CN112651659B - Flood control risk assessment method for water transfer project to left bank area of engineering area - Google Patents

Abstract

The invention relates to a flood control risk assessment method for a left bank area of an engineering area by water transfer engineering, which takes a catchment basin corresponding to a hydraulic structure involved in the water transfer engineering as an assessment unit and comprises the following steps: the method comprises the steps of evaluating the change of original flood control design conditions, analyzing the influence of the change of the river basin underlying surface on design flood, calculating the submerging area, the submerging water level and the submerging water depth aiming at the units with the flood control design conditions changed compared with the original design and the influence of the change of the river basin underlying surface conditions on the design flood, and evaluating the economic loss and the influence population consequence of the flood. The invention has the beneficial effects that: by adopting a systematic and scientific risk assessment method, the flood control influence risk of the catchment watershed corresponding to each type of building involved in the flood engineering can be quantitatively assessed, the method comprises the steps of analyzing and assessing the influence of the change degree of the current actual flood condition compared with the original flood control design condition, the change of the design flood, the change of the original flood control design condition and the change of the underlying surface on the flood design in the watershed, such as the submerging depth and the submerging range of an assessment unit, and the corresponding social economy and population influences, and the like, and provides scientific and technical support for the planning and construction of flood control and disaster reduction and water conservancy engineering.

Description

Flood control risk assessment method for water transfer project to left bank area of engineering area

Technical Field

The invention relates to the technical field of flood control of water transfer engineering, in particular to a flood control risk assessment method for a left bank area of an engineering area by water transfer engineering.

Background

After the cross-river basin water transfer project is built, some original slope surface flow areas are changed into centralized outflow, some small rivers are merged and diverted, the downward drainage channels of natural flood of the water transfer project are cut off or changed, the converging conditions of the river are changed, and the situations of river closure, river harmony and the like are possibly caused. The evaluation on the local flood control influence is already carried out in the early design of the general water diversion project, and corresponding treatment measures are adopted for the flood control influence of buildings, but after the water diversion project is built, social economy development along the project is fast, the design conditions of cross rivers and the local social economy condition are changed, and particularly the conditions of the bottom surface of the river in northern areas, working conditions and the like are changed greatly. Therefore, the change conditions of the flood control design conditions and the actual flood conditions after the flood control design conditions and the actual flood conditions are required to be analyzed, and the change degree of the change conditions is evaluated; and analyzing the change condition of the current river basin characteristic value compared with the design period, and analyzing the influence of the change of the underlying surface on the river basin design flood by adopting an original calculation method with obvious change of the river basin characteristic value. And carrying out detailed flood risk assessment on the influence of the change of the original flood control design condition and the change of the underlying surface on the flood designed in the watershed.

Disclosure of Invention

The invention aims to provide a flood control risk assessment method for a left bank area of an engineering area by a water transfer project, which is used for scientifically and specifically assessing the risk of the change of the original flood control design condition of the water transfer project and the influence of the change of an underlying surface on the flood design of a watershed.

In order to achieve the purpose, the technical scheme of the invention is as follows: a flood control risk assessment method for a left bank area of an engineering area by water transfer engineering takes a catchment basin corresponding to a hydraulic structure involved in the water transfer engineering as an assessment unit, and the hydraulic structure comprises five types: river channel inverted siphon and flood drainage culvert types, flood drainage aqueduct types, channel inverted siphon and culvert type aqueducts, beam type aqueducts and underdrains; a left row inverted siphon and left row culvert type and a left row aqueduct type; the steps of the evaluation method include:

A. evaluating the change of original flood control design conditions, wherein evaluation indexes of the evaluation of the change of the original flood control design conditions comprise: the change of catchment area of the basin, the change of river length, the change of construction land area proportion, the degree of narrowing of the flood section of the upstream river, the change of flood capability of the downstream river, the degree of self-blockage of the building, the risk of easy blockage of the building, and the change of social and economic development;

A1. grading each evaluation index by adopting a grading point, measuring the change degree of a plurality of evaluation indexes by adopting a membership degree concept, and obtaining the fuzzy membership degree of the evaluation indexes to the change degree;

A2. carrying out fuzzy mathematics comprehensive evaluation, grading according to the evaluation indexes of the step A1, and carrying out fuzzy mathematics comprehensive evaluation calculation;

B. analyzing the influence of the condition change of the lower pad surface of the drainage basin on the design flood, and obtaining drainage basin characteristic parameter information above the cross section of each evaluation unit according to DEM data, wherein the drainage basin characteristic parameter information comprises drainage basin water collection area, river length and average specific drop, and is compared with the original design value; and for the evaluation unit with obvious change of the characteristic value, analyzing the influence of the change of the conditions of the underlying surface of the drainage basin on the design flood by adopting the same calculation method as the original design of the water transfer engineering.

C. Aiming at the flood control design condition which is changed compared with the original design and the unit which has influence on the designed flood due to the condition change of the lower surface of the drainage basin, the flood submerging simulation calculation is carried out to obtain the submerging area, the submerging water level and the submerging water depth;

D. flood economic loss and population impact outcome assessment including direct economic loss estimation and flooding impact population estimation.

Further, in order to more scientifically establish an evaluation index system, in step a, in the index of the change evaluation of the originally designed flood control condition, the river basin water collection area change value, the river length change value and the construction land area proportion change value are quantitative indexes, and the upstream river channel flood section narrowing degree, the downstream river channel flood discharge capacity change, the building self-plugging degree, the building easy-plugging risk and the social and economic development change are qualitative indexes; in step a1, three of the rating points are used to classify each of the evaluation indexes into four evaluation grades of no change, general change, large change and significant change.

Further, in order to reasonably grade the evaluation index, the evaluation grading index of the watershed water collection area change value is as follows: no change is less than 10%, the general change belongs to 10-20%, the larger change belongs to 20-30%, and the major change belongs to 30%;

the evaluation grading index of the river length change value is as follows: no change is-5%, the general change belongs to-10% -5%, the larger change belongs to-20% -10%, and the larger change falls below-20%;

the evaluation grading index of the construction land area proportion change value is as follows: no change is less than 3%, the general change belongs to 3-5%, the larger change belongs to 5-10%, and the major change is more than 10%;

the evaluation grading index of the upstream river flood discharge section narrowing degree is as follows:

no change: no river channel is crowded by building houses in rural areas or cities and towns, no river channel is crowded by engineering waste slag, mound and the like,

general variations: building houses in rural areas or towns, abandoning residues in engineering, extruding piled soil to occupy less than 1/3 of the width of a river channel,

the larger the change: building houses in rural areas or towns, abandoning residues in engineering, extruding piled soil to occupy the width of a river channel which is more than 1/3 and less than 2/3,

the great change is that: building houses in rural areas or towns, abandoning residues in engineering, and extruding piled soil to occupy a river channel with a width larger than 2/3;

the evaluation grading index of the downstream river flood discharge capacity change is as follows:

no change: without water-blocking buildings, engineering muck and newly-built roads occupying river channels,

general variations: the width of the water blocking building, the engineering muck, the newly repaired road and the like occupying the river channel is less than 1/3,

the larger the change: the width of the water blocking building, engineering muck, newly repaired road and the like occupying the river is more than 1/3 and less than 2/3, and the method has the following important changes: the width of the river channel occupied by water-blocking buildings, engineering muck, newly-built roads and the like is more than 2/3;

the evaluation grading index of the self-blocking degree of the building is as follows:

no change: the building does not have any clogging per se,

general variations: silt deposition and garbage blockage account for less than 10 percent of the height of the building,

the larger the change: silt deposition and garbage blockage account for more than 10 percent and less than 50 percent of the height of the building,

the great change is that: silt siltation and garbage blockage account for more than 50% of the height of the building;

the evaluation grading index of the building easy-to-block risk is as follows:

no change: the domestic garbage and the tree firewood floater are not arranged near the inlet, the building is far away from the mountain, the vegetation in the drainage basin is good, no geological breaking is caused, the geological disaster is not easy to happen,

general variations: a small amount of floating objects such as domestic garbage, trees, firewood and the like are arranged near the inlet, the proportion is less than 10 percent of the inlet space,

the larger the change: a certain amount of floating objects such as domestic garbage, trees, firewood and the like are arranged near the inlet, the proportion is more than 10 percent and less than 50 percent of the inlet space,

the great change is that: the quantity of domestic garbage, trees, firewood and other floating objects near the inlet is more than 50 percent of the inlet space, or the buildings are close to the mountain, the vegetation in the drainage basin is poor, the geology is broken, and the geological disasters are easy to occur;

the evaluation grading index of the socioeconomic development change is as follows:

no change: the left bank area of the water diversion project is a village,

general variations: the left bank area of the water transfer project is the periphery of the villages and towns,

the larger the change: the left bank area of the water transfer project is a village and a town,

the great change is that: the left bank area of the water transfer project is a city or the periphery of the city.

Further, in order to obtain the scientific evaluation result, in step a2, the fuzzy mathematical synthesis evaluation includes:

A21. establishing a fuzzy relation matrix A of the factor discourse domain X and the comment discourse domain U:

x is the index of flood condition change evaluation corresponding to the evaluation unit, and U is the evaluation index grading corresponding to the evaluation unit, wherein: a is_ijRepresenting the ith factor X in the factor universe X_iCorresponding to the jth level u in the comment domain_jRelative affiliation of;

A22. determining the weight fuzzy vector W of the evaluation factor according to the entropy weight method₁，W₂，…，W_n) Wherein, in the step (A),

A23. and (3) realizing the synthesis of the weight vector W and the fuzzy relation matrix A through fuzzy synthesis operation to obtain a fuzzy comprehensive evaluation result B:

wherein:

for the fuzzy synthesis operator, the fuzzy synthesis operator adopts a weighted average operator

And (3) carrying out synthesis, namely:

A24. performing comprehensive evaluation according to the maximum membership degreeIn principle, take the maximum value maxb of each component of B_jAnd taking the corresponding comment as a final comprehensive evaluation result.

Further, in order to obtain more accurate evaluation index weight, the entropy weight weighting calculation step includes:

a. standardizing data, standardizing data of each index, and giving n indexes X for flood condition change evaluation₁，X₂，…，X_nWherein X is_i＝{x_i1，…，x_ij，…x_iLL is the number of samples, and the value normalized for each index data is Y₁，Y₂，…，Y_nWherein Y is_i＝{y_i1，,…y_ij,…y_iLL, L is the number of samples, 1,2,. n, j is1, 2,. L,

b. calculating the information entropy of each index, and calculating the information entropy of a group of data according to the definition of the information entropy in the information theory

Wherein

If p is_ijWhen 0, then

c. Determining the weight of each index, and calculating the information entropy of each index to be E according to a calculation formula of the information entropy₁，E₂,…，E_n. Calculating the weight of each index through the information entropy:

furthermore, in order to obtain a good analysis result of influence of the change of the underlying surface on the design flood, in the step B, according to 1:5 DEM data, by using an ArcGIS10.1 platform and a hydrologic analysis module Hydrology in a Spatial analysis tool Spatial analysis Tools, basin characteristic parameter information such as a basin catchment area, a river length, an average specific drop and the like above a cross section of each evaluation unit is obtained by a method combining automatic extraction and manual correction, and is compared with an original design value of a water regulation project; and for the evaluation unit with obvious change of the characteristic value, analyzing the influence of the change of the conditions of the underlying surface of the drainage basin on the design flood by adopting the same calculation method as the original design.

Further, in order to obtain an accurate flood inundation simulation calculation result, in step C, the step of flood inundation simulation calculation includes:

a. creating a distinguishing image for storing distinguishing flooding information, wherein the size of the area is the same as that of an evaluation unit (DEM), each pixel is consistent with the size of a DEM grid, and all values of the pixels are given to the elevation value of the flooding water level;

b. marking all grid points smaller than the water level elevation in the area to obtain a possibly submerged area; then, the isolated region is removed, and a set of all grid points with connected associated distribution, namely a flooding area, is found.

Furthermore, in order to obtain an accurate submerging water level, the method for determining the submerging water level includes setting a preset water level, calculating the filling amount by using a Surface analysis function Surface in a 3D Analyst extension module in ArcGIS, and performing trial calculation until the filling amount under the preset water level is close to the flood amount, so as to obtain the submerging water level.

Further, a more specific method for evaluating economic loss of flood and consequences on influencing population is that, in the step D, the evaluation of economic loss of flood and consequences on influencing population includes:

a. direct economic loss estimation:

and (3) field inundation loss:

wherein：L_FarmlandFor economic loss of farmland (ten thousand yuan), O_{First industry}Is the total value (ten thousand yuan) of the first industry, A_{Agricultural land}For agricultural land area (km)²)，A_{Submerging farmland}To submerge the farmland area (km)²)，η_FarmlandIs the farmland flood loss rate (the ratio of the value of farmland loss to the value of farmland property before disaster or in normal years).

Greenfield flooding loss:

L_greenbelt＝R_{Greenery patches remediation}×A_{Submerging green land}×η_Greenbelt

Wherein: l is_GreenbeltFor economic loss in greenland (ten thousand yuan), R_{Greenery patches remediation}Unit price for repairing greenbelt (ten thousand yuan/km)²)，A_{Submerging green land}To submerge in green area (km)²)，η_GreenbeltThe greenfield flood loss rate (the ratio of the value of greenfield loss to the value of the greenfield property before disaster or in the normal year).

The enterprise inundates and loses:

wherein: l is_EnterpriseFor economic loss of enterprise (ten thousand yuan), O_{Fixed assets of an enterprise}For an enterprise fixed asset Total value (ten thousand dollars), N_{Enterprise unit}Number of units of a business, A_{Flooding enterprises}To flood the enterprise area (km)²)，A_EnterpriseFor the land area (km) of the enterprise²)，η_{Industrial and mining enterprises}The flood loss rate of the enterprise (the ratio of the loss value of the enterprise to the property value of the enterprise before the disaster or in the normal year).

And (3) house submerging loss:

L_house＝R_{Affected premises}×A_{Submerged house}×η_House

Wherein: l is_HouseFor economic loss of house (ten thousand yuan), R_{Affected premises}For the unit price of the affected house (ten thousand yuan/km)²)，A_{Submerged house}To submerge a building area (km)²)，η_HouseFor housesFlood loss rate (the ratio of house lost value to the house financial value before disaster or in the normal year).

b. Flooding affects the population:

wherein: p_{Affecting the population}To influence population (people), P_{Total population}Is the total population (people) of the town (village), N_{Number of family}Is the number of families in town (village), A_{Submerged house}To submerge a building area (km)²)，A_{Every family residence}For each family residence area (km)²)。

The invention has the beneficial effects that: by adopting a risk assessment method of systematic science, the influence risk of flood control in catchment watershed corresponding to various types of buildings involved in flood engineering can be quantitatively assessed, the influence risk comprises the variation degree of the current actual flood condition compared with the original flood control design condition, the variation of design flood, the influence of variation of the original flood control design condition and variation of underlying surface on the flood design in the watershed on the submerging depth and submerging range of an assessment unit, and the influence of corresponding social economy, population and the like, and scientific and technical support is provided for the planning and construction of flood control and disaster reduction and water conservancy engineering.

The invention is described in detail below with reference to the figures and examples.

Drawings

FIG. 1 is a membership function graph corresponding to a change in catchment area of a drainage basin and a change in proportion of area of construction land;

FIG. 2 is a graph of membership functions for river length changes;

fig. 3 is a flow chart of flood inundation simulation calculations.

Detailed Description

A flood control risk assessment method for a left bank area of an engineering area by water transfer engineering takes an assessment unit as an object, and the assessment unit is a catchment basin related to various types of hydraulic structures in the water transfer engineering. The present invention divides the hydraulic structure into five types: the channel type of the river channel is inverted siphon type and flood drainage culvert type, the flood drainage aqueduct type is inverted siphon type and culvert type aqueduct type, beam type aqueduct type and closed canal type; the left discharge inverted siphon and left discharge culvert type and the fifth left discharge aqueduct type.

The steps of the evaluation method include:

A. and (5) evaluating the change of original flood control design conditions. The original flood control design condition change evaluation adopts eight evaluation indexes, including: the method comprises the following steps of firstly, changing the catchment area of a drainage basin, secondly, changing the river length, thirdly, changing the proportion of the area of a construction land, fourthly, narrowing the section of an upstream river channel for flood discharge, fifthly, changing the capacity of the downstream river channel for flood discharge, sixthly, changing the self-blocking degree of a building, seventhly, easily blocking the risk of the building, and finally, changing the economic development of society.

A1. And grading each evaluation index by adopting a grading point, measuring the change degree of a plurality of evaluation indexes by adopting a membership degree concept, and obtaining the fuzzy membership degree of the evaluation indexes to the change degree.

The degree of the change of the evaluation index is obtained by adopting a quantitative method and a qualitative method, and the evaluation index is correspondingly divided into a quantitative index and a qualitative index.

The quantitative indexes are obtained by GIS technology comparison and comprise a river basin water collection area change value, a river length change value and a construction floor area proportion change value. And dividing each evaluation index into four evaluation grades of no change, general change, large change and significant change by adopting three grading points.

The evaluation grading index of the watershed water collection area change value is as follows: no change is less than 10%, the general change belongs to 10-20%, the larger change belongs to 20-30%, and the major change belongs to 30%; the three classification points used were 10%, 20%, 30%.

The evaluation grading index of the river length change value is as follows: no change is-5%, the general change belongs to-10% -5%, the larger change belongs to-20% -10%, and the larger change is less than-20%; the three classification points used were-5%, -10%, -20%.

The evaluation grading index of the construction land area proportion change value is as follows: no change is less than 3%, the general change belongs to 3-5%, the larger change belongs to 5-10%, and the major change is more than 10%; the three classification points used were 3%, 5%, 10%.

The calculation algorithm of the membership degree of the two quantitative indexes of the basin catchment area change and the construction land area ratio change is represented as follows:

in the formula, X_iIs one of the two evaluation indexes, beta₁、β₂And beta₃And as three grading points, u is the grading of the evaluation index corresponding to the evaluation unit, and the fuzzy membership of the variation value to the variation grade is calculated through formulas 1 to 4 to obtain a corresponding membership function graph, as shown in fig. 1.

The membership calculation algorithm for the river length change quantitative index is represented as:

in the formula, X_iEvaluating an indicator for said river length variation, beta₁、β₂And beta₃And as three grading points, u is the grading of the evaluation index corresponding to the evaluation unit, and the fuzzy membership of the variation value to the variation grade is calculated through formulas 5 to 8 to obtain a corresponding membership function graph, as shown in fig. 2.

The qualitative indexes are quantitatively graded according to the variation property of the evaluation object, and the qualitative indexes include the degree of narrowing of the flood section of the upstream river, the variation of the flood capability of the downstream river, the self-plugging degree of the building, the easy-plugging risk of the building, and the social and economic development variation. And dividing each evaluation index into four evaluation grades of no change, general change, large change and great change by adopting three grading points. After the qualitative index is determined to belong to a certain class, the membership degree of the qualitative index is directly given as 1.

The evaluation grading index of the upstream river flood discharge section narrowing degree is as follows:

no change: no river channel is crowded by building houses in rural areas or cities and towns, no river channel is crowded by engineering waste slag, mound and the like,

general variations: building houses in rural areas or towns, abandoning residues in engineering, extruding piled soil to occupy less than 1/3 of the width of a river channel,

the larger the change: building houses in rural areas or towns, abandoning residues in engineering, extruding piled soil to occupy the width of a river channel which is more than 1/3 and less than 2/3,

the great change is that: building houses in rural areas or towns, abandoning residues in engineering, and extruding piled soil to occupy a river channel with a width larger than 2/3;

the three classification points used were 0, 1/3, 2/3.

The evaluation grading index of the downstream river flood discharge capacity change is as follows:

no change: without water-blocking buildings, engineering muck and newly-built roads occupying river channels,

general variations: the width of the water blocking building, the engineering muck, the newly repaired road and the like occupying the river channel is less than 1/3,

the larger the change: the width of the water blocking building, engineering muck, newly repaired road and the like occupying the river is more than 1/3 and less than 2/3, and the method has the following important changes: the width of the river channel occupied by water-blocking buildings, engineering muck, newly-built roads and the like is more than 2/3;

the three classification points used were 0, 1/3, 2/3.

The evaluation grading index of the self-blocking degree of the building is as follows:

no change: the building does not have any clogging per se,

general variations: silt deposition and garbage blockage account for less than 10 percent of the height of the building,

the larger the change: silt deposition and garbage blockage account for more than 10 percent and less than 50 percent of the height of the building,

the great change is that: silt siltation and garbage blockage account for more than 50% of the height of the building;

the three classification points used were 0, 10%, 50%.

The evaluation grading index of the building easy-to-block risk is as follows:

no change: the domestic garbage and the tree firewood floater are not arranged near the inlet, the building is far away from the mountain, the vegetation in the drainage basin is good, no geological breaking is caused, the geological disaster is not easy to happen,

general variations: a small amount of floating objects such as domestic garbage, trees, firewood and the like are arranged near the inlet, the proportion is less than 10 percent of the inlet space,

the larger the change: a certain amount of floating objects such as domestic garbage, trees, firewood and the like are arranged near the inlet, the proportion is more than 10 percent and less than 50 percent of the inlet space,

the great change is that: the quantity of domestic garbage, trees, firewood and other floating objects near the inlet is more than 50 percent of the inlet space, or the buildings are close to the mountain, the vegetation in the drainage basin is poor, the geology is broken, and the geological disasters are easy to occur;

the three classification points used were 0, 10%, 50%.

The evaluation grading index of the socioeconomic development change is as follows:

no change: the left bank area of the water diversion project is a village,

general variations: the left bank area of the water transfer project is the periphery of the villages and towns,

the larger the change: the left bank area of the water transfer project is a village and a town,

the great change is that: the left bank area of the water transfer project is a city or the periphery of the city.

The three classification points adopted are villages, towns and cities.

A2. And D, carrying out fuzzy mathematics comprehensive evaluation, grading according to the evaluation indexes of the step A1, and carrying out fuzzy mathematics comprehensive evaluation calculation. The fuzzy mathematical comprehensive evaluation comprises the following steps:

A21. establishing a fuzzy relation matrix A of the factor discourse domain X and the comment discourse domain U:

x is the index of flood condition change evaluation corresponding to the evaluation unit, and U is the evaluation index grading corresponding to the evaluation unit, wherein: a is_ijRepresenting the ith factor X in the factor universe X_iCorresponding to the jth level u in the comment domain_jRelative affiliation of;

A22. determining the weight fuzzy vector W of the evaluation factor according to the entropy weight method₁，W₂，…，W_n) Wherein, in the step (A),

the basic idea of the entropy weight method is to determine objective weights according to the size of index variability. Generally, if the information entropy E of a certain index is E_jThe smaller the index value, the larger the variation degree, the more the information amount provided, the larger the effect in the comprehensive evaluation, and the larger the weight. In contrast, the information entropy E of a certain index_jThe larger the index value, the smaller the degree of variation, the smaller the amount of information provided, the smaller the effect exerted in the overall evaluation, and the smaller the weight.

The entropy weight method weighting calculation steps of the invention are as follows:

a. and (6) standardizing data. Standardizing the data of each index, and giving n indexes X for flood condition change evaluation₁，X₂，…，X_nWherein X is_i＝{x_i1，…，x_ij，…x_iLL is the number of samples, and the value normalized for each index data is Y₁，Y₂，…，Y_nWherein Y is_i＝{y_i1，，…y_ij，…y_iLL, L is the number of samples, 1,2,. n, j is1, 2,. L,

b. and solving the information entropy of each index. According to the definition of information entropy in information theory, the information entropy of a group of data

Wherein

If p is_ijWhen 0, then

c. Determining each index weight. According to the calculation formula of the information entropy, calculating the information entropy of each index to be E₁，E₂，…，E_n. Calculating the weight of each index through the information entropy:

A23. and (3) realizing the synthesis of the weight vector W and the fuzzy relation matrix A through fuzzy synthesis operation to obtain a fuzzy comprehensive evaluation result B:

wherein:

for the fuzzy synthesis operator, the fuzzy synthesis operator adopts a weighted average operator

And (3) carrying out synthesis, namely:

A24. carrying out comprehensive evaluation, and taking the maximum value maxb of each component of B according to the maximum membership rule_jAnd taking the corresponding comment as a final comprehensive evaluation result.

B. Analyzing the influence of the condition change of the lower pad surface of the drainage basin on the design flood, and obtaining drainage basin characteristic parameter information above the cross section of each evaluation unit according to DEM data, wherein the drainage basin characteristic parameter information comprises drainage basin water collection area, river length and average specific drop, and is compared with the original design value; for an evaluation unit with obvious change of the characteristic value (such as a unit with the river basin area increased by more than 20% or the river length reduced by more than 10%), the influence of the change of the river basin underlying surface condition on the design flood is analyzed by adopting the same calculation method as the original design of the water diversion engineering.

The more specific method is as follows: according to 1:5 million DEM data, acquiring watershed characteristic parameter information such as watershed water collection area, river length, average specific gravity and the like above cross sections of each evaluation unit by using an ArcGIS10.1 platform and a hydrological analysis module in Spatial analysis Tools through a method combining automatic extraction and manual correction, and comparing the watershed characteristic parameter information with an original design value of a water regulating project; and for the evaluation unit with obvious change of the characteristic value, analyzing the influence of the change of the conditions of the underlying surface of the flow field on the design flood by adopting the same calculation method as the original design.

The flood rechecking method corresponding to the actual flow measurement data comprises the following steps: and calculating according to the measured flow data of the hydrological station. And if the flood extension series has extra-large rainstorm flood, rechecking the calculation parameters of the design flood and calculating the design flood.

The flood rechecking method corresponding to the data without measured flow comprises the following steps: for rivers without measured flow data, the design flood of the cross section is calculated by a method of calculating the design flood through designing rainstorm according to the method in the atlas of the region where the river is located according to the regulations of the design flood calculation Specification for Water conservancy and hydropower engineering (SL 44-2006). The drainage basin output flow is calculated by designing rainstorm through the rainfall runoff relation recommended in the atlas, the rainfall runoff relation of part of areas is checked and adjusted, and the adjusted rainfall runoff relation is used for calculation. And selecting and determining a rainstorm period and a flood period according to the size of the drainage basin and the characteristics of the rain flood in different drainage basins. For rivers with large drainage basin area and long duration of rainstorm flood, 3d design of rainstorm is available to calculate drainage basin runoff; and for the drainage basin with small area and the duration of the rainstorm flood within 1d, calculating the drainage basin runoff rate by designing the rainstorm for 24 h.

C. Aiming at the flood control design condition, the flood control design condition is changed compared with the original design, and the flood flooding simulation calculation is carried out on the units which have influences on the design flood due to the condition change of the lower pad surface of the drainage basin, so that the flooding area, the flooding water level and the flooding water depth are obtained.

More specifically, the flood inundation simulation calculation is carried out by taking ArcGIS10.1 as a supporting platform according to the concept of 'plane simulation'. The method comprises the following specific steps:

a. creating a distinguishing image which is specially used for storing distinguishing submerging information, wherein the size of the distinguishing image is the same as that of a research area DEM, each pixel is consistent with the size of a DEM grid, and the values of the pixels are all given to the elevation value of the submerging water level;

b. marking all grid points smaller than the water level elevation in the area to obtain a possibly submerged area; then, the isolated region is removed, namely the region which is not communicated with the actual inundated region is removed, and the set of all grid points with the communication association distribution is found, so that the actual inundated region is determined.

When the flood simulation calculation is carried out by using a plane simulation method, a key problem is how to determine the submergence level. Knowing the process of a flood, the flood volume in the flood generation period can be counted according to the peak flow and the duration of the flood in different periods. As shown in fig. 3, a preset water level is set, the Surface analysis function Functional Surface in the 3D analysis extension module in ArcGIS is used to calculate the filling amount, and after trial calculation, the filling amount under the preset water level is close to the design flood amount with different frequencies, that is, the flooding water level corresponding to the flood in the field is obtained, so that the flooding area and the average flooding depth can be calculated.

D. Flood economic loss and population impact outcome assessment including direct economic loss estimation and flooding impact population estimation.

a. Direct economic loss estimation:

and (3) field inundation loss:

wherein: l is_FarmlandFor economic loss of farmland (ten thousand yuan), O_{First industry}Is the total value (ten thousand yuan) of the first industry, A_{Agricultural land}For agricultural land area (km)²)，A_{Submerging farmland}To submerge the farmland area (km)²)，η_FarmlandIs the farmland flood loss rate (the ratio of the value of farmland loss to the value of farmland property before disaster or in normal years).

Greenfield flooding loss:

L_greenbelt＝R_{Greenery patches remediation}×A_{Submerging green land}×η_Greenbelt(formula 13)

Wherein: l is_GreenbeltFor economic loss in greenland (ten thousand yuan), R_{Greenery patches remediation}Unit price for repairing greenbelt (ten thousand yuan/km)²)，A_{Submerging green land}To submerge a greenbelt area (km)²)，η_GreenbeltThe greenfield flood loss rate (the ratio of the value of greenfield loss to the value of the greenfield property before disaster or in the normal year).

The enterprise inundates and loses:

wherein: l is_EnterpriseFor economic loss of enterprise (ten thousand yuan), O_{Fixed assets of an enterprise}For an enterprise fixed asset Total value (ten thousand dollars), N_{Enterprise unit}Number of units of a business, A_{Flooding enterprises}To flood the enterprise area (km)²)，A_EnterpriseFor the land area (km) of the enterprise²)，η_{Industrial and mining enterprises}The flood loss rate of the enterprise (the ratio of the loss value of the enterprise to the property value of the enterprise before the disaster or in the normal year).

And (3) house submerging loss:

L_house＝R_{Affected premises}×A_{Submerged house}×η_House(formula 15)

Wherein: l is_HouseFor economic loss of house (ten thousand yuan), R_{Affected premises}For the unit price of the affected house (ten thousand yuan/km)²)，A_{Submerged house}To submerge a building area (km)²)，η_HouseThe house flood loss rate (the ratio of the house loss value to the house financial value before the disaster or in the normal year).

The flood damage rate refers to the ratio of the loss value of each property to the original value of each property before the flood or in the normal year. Factors affecting the loss rate of flood disasters are many, such as the degree of flooding (water depth, duration, etc.), property types, disaster seasons, rescue measures, etc. Generally, a relation curve or a relation table of flood damage rate and submergence degree (water depth, duration, flow rate, flood-avoiding time) is respectively established according to different regions and categories of disaster-bearing bodies.

b. Flooding affects the population:

flooding influences are indirectly derived from the area of the affected house within the flooding domain. Firstly, estimating the number of affected families according to the total area of affected houses in a submerging range, then obtaining the average number of residents of each family in cities and towns (villages) according to population data in the statistical yearbook of each region, and further estimating the affected population:

wherein: p_{Affecting the population}To influence population (people), P_{Total population}Is the total population (people) of the town (village), N_{Number of family}Is the number of families in town (village), A_{Submerged house}To submerge a building area (km)²)，A_{Every family residence}For each family residence area (km)²)。

Based on the superposition analysis function of ArcGIS software, the flooding map layer is superposed with the administrative district, land utilization and residential map layer by combining remote sensing images to obtain the distribution of affected farmlands, greenbelts, residential areas and industrial and mining enterprises in the flooding range under different schemes of the evaluation unit, and then the direct economic loss and the population affected by flooding are estimated according to the method.

The first embodiment is as follows:

in this embodiment, for a certain section of the left bank area in the actual water diversion project, the risk assessment method provided by the present invention is adopted to perform quantitative assessment on the flood control influence risk of each design unit, including analysis and assessment of the influence on the change degree compared with the original flood control design condition, the submergence depth and the submergence range of the original design unit, and the corresponding social economy and population, etc., to obtain the following assessment processes and results:

1) evaluation of original flood control design condition change

And analyzing the change of the actual flood conditions of the current situation compared with the original flood control design conditions. In this embodiment, the left bank area includes nineteen evaluation units, and the evaluation units are divided into five types according to the corresponding hydraulic structures:

the sand pit ditches are of river channel inverted siphon and flood discharge culverts;

the oxtail middle branch and the small Mongolian village are of a flood discharge aqueduct type;

the Qili river, the Baima river, the Xiaoma river and the Li Yangye river are of inverted siphon, culvert aqueduct, beam aqueduct and underdrain types;

the kou ditch, the Liang-sourced store ditch, the Fengtang ditch, the Lutinge ditch, the Zhongxiyang ditch, the Liujiazhuang ditch, the BeizhongFeng ditch, the former five Guoguo store ditch and the five Guoguo store ditch are of left-row inverted siphon type and left-row culvert type;

zhangdong ditch, Zhao Guzhuang ditch and Huining ditch are of the type of the left row aqueduct.

A. The basic information of each evaluation unit is as follows:

table-evaluation unit quantitative index change

Qualitative grading of Table two evaluation units

B. Evaluation unit one-factor fuzzy evaluation

And evaluating the change degree of the flood control design conditions of the left bank area of the engineering area and the actual flood conditions after construction according to 4 grades, namely no change, general change, large change and great change. And each flood risk evaluation unit classifies and lists the evaluation matrix of the single factor according to the building type.

And according to various actual materials and research data of the engineering project risk evaluation, carrying out quantitative estimation on each evaluation index by adopting a fuzzy mathematical method, and then sequentially evaluating each index according to the determined evaluation grade standard. On the basis, the evaluation matrix of the single element in each subset is obtained respectively, and the evaluation matrix is shown in the third table.

Evaluation index evaluation matrix example of inverted siphon and flood discharge culvert of table three river channels

According to the five types of hydraulic buildings related to the water transfer project, the evaluation matrix is divided into five categories, and the categories are defined as river channel inverted siphon and flood discharge culverts A₁Drainage flume A₂Inverted siphon and culvert aqueduct, beam aqueduct and underdrain A₃(ii) a Left-row inverted siphon and left-row culvert A₄Left row aqueduct A₅。

The evaluation indexes of corresponding evaluation units of five different types of hydraulic buildings are different: for example, the flood discharge aqueduct and the left flood discharge aqueduct do not relate to the self-clogging degree of the building, and the inverted siphon, the culvert type aqueduct, the beam type aqueduct and the closed channel do not relate to the self-clogging degree of the building and the easy-clogging risk of the building. The evaluation indexes of various types of hydraulic buildings are shown in the fourth table.

Evaluation index of corresponding evaluation unit of four types of hydraulic buildings

According to the evaluation units contained in each large type of hydraulic structure, the evaluation matrixes of 19 evaluation units are respectively defined, and the evaluation matrixes specifically comprise: shawo gou A₁₁The middle branch of oxtail A₂₁Small mengchun river a₂₂Qilihe A₃₁White horse river A₃₂Small horse river A₃₃Li Yanghe A₃₄Oral sulcus A₄₁Beam source store ditch A₄₂Von Tanggou A₄₃Lu Ting ditch A₄₄Middle house sunny ditch A₄₅Liu Jia Zhuang ditch A₄₆Northern Feng Gou A₄₇Front five Guo store ditch A₄₈Grove of five guo shops a₄₉Zhangdongcao A₅₁Zhao Guzhuang ditch A₅₂Huining gou A₅₃。

According to the analysis of the evaluation indexes, the judgment matrix of each evaluation unit single factor can be obtained as follows:

sand pit ditch A of river course inverted siphon₁₁:

Wherein:

the first is the relative membership degree of the change of the water collecting area of the sand pit ditch basin of the inverted siphon of the riverway relative to four change levels. As can be seen from Table I, the catchment area of the drainage basin of the sand pit ditch is changed to-3%, and the membership degree corresponding to each grade is [1,0,0,0] according to the formulas (1) to (4).

The second action is relative membership degree of the change of the length of the sand pit ditch of the inverted siphon of the riverway relative to four change grades. As can be seen from Table I, the river length of the sand pits varies by-6.9%, and the degrees of membership corresponding to the respective grades are [0,0.62,0.38, 0] according to the formulae (5) to (8).

The third row is relative membership degree of the proportional change of the area of the sand pit ditch construction of the inverted siphon of the riverway relative to four change levels. As can be seen from Table I, the proportion of the area of the construction land of the sand pit ditch is changed to-1%, and the membership degree corresponding to each grade is [1,0,0,0] according to the formulas (1) to (4).

The fourth row is relative affiliation degree of the narrowing degree of the flood discharge section of the river channel upstream of the sand pit ditch of the inverted siphon of the river channel relative to four change levels. As can be seen from the second table, the flood section of the upstream river of the sand pit ditch is not narrow and is unchanged, so that the membership degree corresponding to each grade is [1,0,0,0 ].

The fifth element is relative membership degree of flood discharge capacity change of a river channel downstream of the sand pit ditch of inverted siphon of the river channel relative to four change levels. As can be seen from table two, the downstream river of the sand pit ditch occupies the river without the water-blocking structures, and is unchanged, so the membership degree corresponding to each grade is [1,0,0,0 ].

And the sixth action is relative membership degree of the self clogging degree of the sand pit ditch building with inverted siphon of the river channel relative to four change levels. As can be seen from Table II, the sand pit ditch itself is clogged by less than 10%, and is a general variation, so that the membership degree corresponding to each grade is [0,1,0,0 ].

And the seventh behavior is relative membership of the blockage-prone risk of the sand pit ditch building with inverted siphon of the riverway relative to four change levels. As can be seen from the second table, a small amount of floating objects such as domestic garbage and the like exist near the sand pit ditch inlet, and the floating objects belong to general changes, so that the membership degree corresponding to each grade is [0,1,0,0 ].

The eighth line is the relative membership degree of the social and economic development change of the sand pit ditch with inverted siphon of the riverway relative to four change levels. As can be seen from the second table, the social and economic development of the sand pit ditch is unchanged, and the sand pit ditch belongs to no change. So that its membership degree corresponding to each grade is [1,0,0,0 ].

The judgment matrix of the single factor of other evaluation units is calculated according to the method, and is not described again.

Oxtail middle branch A of flood discharge aqueduct₂₁：

Small Mongcun river A of flood discharge aqueduct₂₂：

Channel inverted siphon qili river A₃₁：

White horse river A with inverted siphon channels₃₂：

Small river a with inverted siphon canal₃₃：

Channel inverted siphon Li Yanghe A₃₄：

Head ditch A of inverted siphon for drainage₄₁：

Beam source store ditch A with inverted siphon drainage₄₂：

Von Tanggou A of drainage inverted siphon₄₃：

Drainage inverted siphon rutting ditch A₄₄：

Drainage inverted siphon middle house sunny ditch A₄₅：

Liu Jiazhuang ditch A with inverted siphon drainage₄₆：

North middle Von ditch A of inverted siphon drainage₄₇：

Front five Guo store ditch A with inverted siphon for drainage₄₈：

Drainage inverted siphon five guo shop ditch A₄₉：

Zhangdongchun A of drainage aqueduct₅₁：

Zhao Guzhuang ditch A of drainage aqueduct₅₂：

Huining ditch A of drainage aqueduct₅₃：

C. Determination of index weight by entropy weight method

In the comprehensive evaluation model, aiming at different building types, the evaluation index data of various buildings are subjected to standardization treatment according to the corresponding evaluation index content, the information entropy of each index is obtained, the weight of each index is determined through the information entropy, and the weight is respectively as follows:

evaluation index weight W of inverted siphon and flood discharge culvert of river channel₁：

W₁Building self clogging degree of change of building easy risk social and economic development change of construction site area ratio change of river basin water collection area change construction site area narrowing degree of upstream river channel flood passage section and downstream river channel flood passage capacity change]

Not [ 0.1070.1070.0000.1730.2230.2190.000 ] (formula 36)

W₁The calculation process of (2) is as follows:

from the calculation result of the formula 17, the indexes of the sand pit ditch of the inverted siphon of the river channel belong to the grades of 1,2, 1, 1, 1,2, 2 and 1 respectively, as shown in the fifth and tenth rows of the table. Since the evaluation range of this embodiment only relates to a certain section of left bank area in the actual engineering area, to obtain the weights of the indexes of the buildings of this type, the grades of the evaluation indexes of all the buildings of the same type in the entire engineering area are also required, as shown in the following table (table five).

Table five grades of inverted siphon and flood discharge culvert of river channel

By formulae in entropy weight

The data of the above indices were normalized, and the normalized results are shown in the following table (table six).

Table six river channel inverted siphon and flood discharging culvert each evaluation index belonged grade standardization result

According to formula in entropy weight method by table six

The information entropy of each index can be obtained, as shown in the following table (table seven).

Information entropy of evaluation indexes of inverted siphons and flood discharge culverts of seven river channels in table

By formulae in entropy weight

The weights of the indexes of the river inverted siphon and the flood discharge culvert can be obtained, and are shown in the following table (table eight).

Table eight river channel inverted siphon and flood discharging culvert each evaluation index weight

The method for calculating the weight of indexes such as flood discharge aqueducts, inverted siphons of channels, culvert type aqueducts and the like of other types of buildings is similar to that of W1, and the calculation results are as follows:

weight W2 of flood discharge aqueduct:

W₂construction land area ratio change of river basin water collection area change construction land area ratio change upstream river channel flood discharge section beam narrow degree change downstream river channel flood discharge capacity change building easy-blockage risk social and economic development change]

Not [ 0.0910.1360.1880.1690.2780.1390.000 ] (formula 37)

Weight W of inverted siphon, culvert aqueduct, beam aqueduct and underdrain of channel₃：

W₃Change of construction land area ratio of river basin water collection area change construction land area change upstream river channel flood discharge section beam narrow degree and change of downstream river channel flood discharge capacity]

Not [ 0.0460.0000.1470.3200.4870.000 ] (formula 38)

Weight W4 of left-row inverted siphon and left-row culvert:

W₄building self clogging degree of building self clogging degree easy to risk social and economic development change of construction site area ratio change upstream river channel flood passage section beam narrow degree and downstream river channel flood passage capacity change building self clogging degree]

Not rate [ 0.0860.1810.1430.1590.2190.0880.1230.000 ] (formula 39)

Weight W5 of drainage aqueduct:

W₅construction land area ratio change of river basin water collection area change construction land area ratio change upstream river channel flood discharge section beam narrow degree change downstream river channel flood discharge capacity change building easy-blockage risk social and economic development change]

Not [ 0.0910.1360.1880.1690.2780.1390.000 ] (formula 40)

D. Fuzzy comprehensive evaluation

According to the principle of the fuzzy comprehensive evaluation, the change comprehensive evaluation matrix of the current flood-driving conditions of the left bank area of the water transfer engineering area compared with the original flood-control design conditions can be expressed as follows:

wherein, W is a weight matrix of various buildings obtained by an entropy weight method, A is a judgment matrix of each evaluation unit according to a single-factor evaluation method, and n is the number of evaluation indexes of different building types.

Through calculation, the comprehensive evaluation matrix of each evaluation unit is as follows:

sand pit ditch B of river course inverted siphon₁₁:

B₁₁＝[0.453 0.5083 0.0407 0](formula 42)

The maximum membership is 0.5083, and the degree of change is 2 grades, and the degree of change is general.

Oxtail middle branch B of flood discharge aqueduct₂₁：

B₂₁＝[0.7385 0.0744 0.1007 0](formula 43)

Wherein, the maximum membership is 0.7385, the degree of change is1 grade, and there is no change.

Small Mongchun river B of flood discharge aqueduct₂₂：

B₂₂＝[0.584 0.139 0.278 0](formula 44)

Wherein, the maximum membership degree is 0.584, the grade of the variation degree is1 grade, and no variation exists.

Channel inverted siphon seven river B₃₁：

B₃₁＝[0.9798 0.0202 0 0](formula 45)

Wherein, the maximum membership is 0.9798, the degree of change is1 grade, and there is no change.

White horse river B with inverted siphon channels₃₂：

B₃₂＝[0.513 0.487 0 0](formula 46)

Wherein, the maximum membership degree is 0.513, the grade of the variation degree is1 grade, and no variation exists.

Small river B with inverted siphon canal₃₃：

B₃₃＝[1 0 0 0](formula 47)

Wherein, the maximum membership degree is1, the grade of the variation degree is1 grade, and the variation degree is unchanged.

Channel inverted siphon Li Yanghe B₃₄：

B₃₄＝[1 0 0 0](formula 48)

Wherein, the maximum membership degree is1, the grade of the variation degree is1 grade, and the variation degree is unchanged.

Head ditch B of inverted siphon for drainage₄₁：

B₄₁＝[0.7417 0.2573 0 0](formula 49)

Wherein, the maximum membership is 0.7417, the degree of change is1 grade, and there is no change.

Beam source store ditch B with inverted siphon drainage₄₂：

B₄₂＝[0.695 0.123 0.0418 0.1392](formula 50)

Wherein, the maximum membership degree is 0.695, the grade of the variation degree is1 grade, and no variation exists.

Von Tanggou B with inverted siphon drainage₄₃：

B₄₃＝[0.695 0.157 0.147 0](formula 51)

Wherein, the maximum membership degree is 0.695, the grade of the variation degree is1 grade, and no variation exists.

Drainage inverted siphon rutting ditch B₄₄：

B₄₄＝[0.4933 0.2866 0.219 0](formula 52)

Wherein, the maximum membership is 0.4933, the degree of change is1 grade, and there is no change.

Middle house sunny ditch B with inverted siphon drainage₄₅：

B₄₅＝[0.317 0.282 0.3786 0.0213](formula 53)

Wherein, the maximum membership degree is 0.3786, the grade of the variation degree is 3 grades, and the variation degree is not changed greatly.

Liu Jiazhuang ditch B with inverted siphon drainage function₄₆：

B₄₆＝[0.476 0.123 0.37 0.029](formula 54)

Wherein, the maximum membership degree is 0.476, the grade of the variation degree is1 grade, and no variation exists.

North middle Von ditch B for inverted siphon drainage₄₇：

B₄₇＝[0.876 0.123 0.0906 0](formula 55)

Wherein, the maximum membership degree is 0.876, the grade of the variation degree is1 grade, and no variation exists.

Front five Guo store ditch B with inverted siphon for drainage₄₈：

B₄₈＝[0.657 0.123 0 0.219](formula 56)

Wherein, the maximum membership degree is 0.657, the grade of the variation degree is1 grade, and no variation exists.

Water drainage inverted siphon five guo shop ditch B₄₉：

B₄₉＝[0.528 0.252 0.219 0.44](formula 57)

Wherein, the maximum membership degree is 0.528, the grade of the variation degree is1 grade, and no variation exists.

Zhangdongchun B of drainage aqueduct₅₁：

B₅₁＝[0.3243 0.4054 0.0832 0.188](formula 58)

The maximum membership is 0.4054, and the degree of change is 2 grades, and the degree of change is general.

Zhao Guzhuang ditch B of drainage aqueduct₅₂：

B₅₂＝[0.496 0.1664 0.3386 0](formula 59)

Wherein, the maximum membership degree is 0.496, the grade of the change degree is1 grade, and no change exists.

Huining ditch B of drainage aqueduct₅₃：

B₅₃＝[0.444 0.0482 0.4753 0.0334](formula 60)

Wherein, the maximum membership is 0.4753, the degree of change is 3 grades, and the change is larger.

Through comprehensive evaluation, the current flood conditions of the inverted siphon of the drainage of the male ditches of the middle house and the drainage aqueduct of the Hunning ditch are greatly changed compared with the original flood control design conditions, the inverted siphon of the drainage of the sand pit ditch river channel and the drainage aqueduct of the Zhangdong ditch are generally changed, and the rest 15 units are unchanged.

2) Analysis of influence of river basin underlying surface condition change on design flood

According to the principle of selecting the lower mat surface with larger change (namely, a unit with the catchment area of the drainage basin increased by more than 20% or the river length reduced by more than 10%), selecting the influence of the change of the inverted siphon lower mat surface for drainage of the beam source store on the design flood of the drainage basin. Based on 1:5 ten thousand DEM, hydrological analysis modules (Hydrology) in Spatial analysis Tools (Spatial analysis Tools) are adopted to obtain drainage basin characteristic parameter information such as drainage basin catchment area, river length, average ratio reduction and the like above the beam source store ditch cross section by a method combining automatic extraction and manual correction, and the drainage basin characteristic parameter information is compared with an original design value and is shown in the following tables (table nine and table ten).

Table nine present state cross section basic condition table

Comparing the characteristic value of table ten current state drainage basin with the design time

Analyzing and calculating according to the method for analyzing and calculating the influence of the change of the underlying surface condition of the drainage basin on the design flood introduced in the step 2, wherein the result of analyzing and calculating the influence of the change of the underlying surface on the design flood of the drainage basin is as follows:

analysis result of influence of surface eleven underlying surface changes on basin design flood

3) Left bank region flood inundation calculation

Aiming at the flood control design condition, the flood control design condition is changed compared with the original design, and the flood flooding simulation calculation is carried out on the units which have influences on the design flood due to the condition change of the lower pad surface of the drainage basin, so that the flooding area, the flooding water level and the flooding water depth are obtained. And (3) carrying out detailed risk evaluation on 5 evaluation units, namely the beam source store ditch, the Huining ditch, the Zhongcheng sunny ditch, the sand pit ditch and the Zhangzhuang ditch which have influence on the basin design flood due to the change of the original flood control design conditions and the change of the underlying surface, and calculating the submerging range and the water depth by using the flood submerging calculation method introduced in the step 3.

The statistical information of the submerging characteristics of each evaluation unit is shown in a table (table twelve), submerging characteristic parameters such as total submerging area, average and maximum submerging water depth, submerging area with water depth respectively larger than 2m and 3m and the like of the left bank area under the working conditions of 5 years and 20 years of each unit and design flood and check flood are respectively counted, and the submerging characteristic parameters are used for describing the submerging degree of the left bank area.

Statistical table of left bank inundation characteristics of twelve evaluation units

4) Flood economic loss and population impact consequence assessment

According to the remote sensing image, in the 5 evaluation units, the farmland is basically all in the flow areas of the beam source store ditch and the Zhangzhuang ditch, wherein industrial and mining enterprises are distributed in the flow areas of the Zhangzhuang ditch, and a small part of enterprise workshops can be submerged in flood in 200 years. The villages flow through the upstream of the middle house sunny ditches and the sand pit ditches, the population is relatively dense, the influence of the left bank submerging on the population and the house is large, the middle house sunny ditches are sloping water areas, although the submerging range is large, the average submerging depth is small, and the direct economic loss caused by the small submerged ditches is smaller than that of the sand pit ditches. Villages are arranged at the upstream of the guining drainage area, but the positions of the villages are relatively high, so that the villages have small influence on population and houses. The farmland is not submerged by flood in 5 years in each unit, and villages are not affected by flood in 20 years. According to the economic statistical yearbook of a certain year in a certain city, the agricultural land production value per unit area is 2609 yuan/mu, and the agricultural land inundation economic loss value can be counted. And (4) obtaining the specific information of the influenced population and the economic evaluation of the submerged areas of each evaluation unit by using the flood economic loss and the influenced population post-result evaluation method introduced in the step (4), and the specific information is shown in the following table (table thirteen).

Economic and social influence evaluation statistical table for thirteen evaluation units

Claims (9)

1. A flood control risk assessment method for a left bank area of an engineering area by water transfer engineering is characterized in that the assessment method takes a catchment basin corresponding to a hydraulic structure involved in the water transfer engineering as an assessment unit, and the hydraulic structure comprises five types: river channel inverted siphon and flood drainage culvert types, flood drainage aqueduct types, channel inverted siphon and culvert type aqueducts, beam type aqueducts and closed channels types, left row inverted siphon and left row culvert types and left row aqueducts types; the steps of the evaluation method include:

A. evaluating the change of original flood control design conditions, wherein evaluation indexes of the evaluation of the change of the original flood control design conditions comprise: the method comprises the following steps of (1) changing the catchment area of a drainage basin, changing the river length, changing the proportion of the area for construction, narrowing the section of an upstream river channel for flood discharge, changing the flood discharge capacity of a downstream river channel, changing the self clogging degree of a building, easily clogging risks of the building and changing the social and economic development;

A1. grading each evaluation index by adopting a grading point, measuring the change degree of a plurality of evaluation indexes by adopting a membership degree concept, and obtaining the fuzzy membership degree of the evaluation indexes to the change degree;

A2. carrying out fuzzy mathematics comprehensive evaluation, grading according to the evaluation indexes of the step A1, and carrying out fuzzy mathematics comprehensive evaluation calculation;

B. analyzing the influence of the condition change of the lower cushion surface of the drainage basin on the design flood, and obtaining drainage basin characteristic parameter information above the cross section of each evaluation unit according to DEM data, wherein the drainage basin characteristic parameter information comprises drainage basin water collection area, river length and average specific drop, and is compared with the original design value; for the evaluation unit with obvious change of the characteristic value, analyzing the influence of the change of the conditions of the underlying surface of the drainage basin on the design flood by adopting the same calculation method as the original design of the water transfer engineering;

C. aiming at the flood control design condition which is changed compared with the original design and the unit which has influence on the designed flood due to the condition change of the lower surface of the drainage basin, the flood submerging simulation calculation is carried out to obtain the submerging area, the submerging water level and the submerging water depth;

D. flood economic loss and population impact outcome assessment including direct economic loss estimation and flooding impact population estimation.

2. The method for assessing the flood control risk of the water transfer engineering on the left bank area of the engineering area according to claim 1, wherein in the step a, in the indexes of the change assessment of the originally designed flood control conditions, the variation value of the catchment area of the drainage basin, the variation value of the river length and the variation value of the proportion of the construction land area are quantitative indexes, and the narrowing degree of the flood section of the upstream river channel, the change of the flood control capacity of the downstream river channel, the clogging degree of the building, the risk of easy blockage of the building and the change of the socioeconomic development are qualitative indexes; in step a1, each of the evaluation indexes is classified into four evaluation grades of no change, general change, large change, and significant change using three of the classification points.

3. The flood control risk assessment method for the left bank area of the engineering area by the water diversion project according to claim 2,

the evaluation grading index of the watershed water collection area change value is as follows: no change is less than 10%, the general change belongs to 10-20%, the larger change belongs to 20-30%, and the major change belongs to 30%;

the evaluation grading index of the river length change value is as follows: no change is-5%, the general change belongs to-10% -5%, the larger change belongs to-20% -10%, and the larger change falls below-20%;

the evaluation grading index of the construction land area proportion change value is as follows: no change is less than 3%, the general change belongs to 3-5%, the larger change belongs to 5-10%, and the major change is more than 10%;

the evaluation grading index of the upstream river flood discharge section narrowing degree is as follows:

no change: no river channel is crowded by building houses in rural areas or cities and towns, no river channel is crowded by engineering waste slag, mound and the like,

general variations: building houses in rural areas or towns, abandoning residues in engineering, extruding piled soil to occupy less than 1/3 of the width of a river channel,

the larger the change: building houses in rural areas or towns, abandoning residues in engineering, extruding piled soil to occupy the width of a river channel which is more than 1/3 and less than 2/3,

the great change is that: building houses in rural areas or towns, abandoning residues in engineering, and extruding piled soil to occupy a river channel with a width larger than 2/3;

the evaluation grading index of the downstream river flood discharge capacity change is as follows:

no change: without water-blocking buildings, engineering muck and newly-built roads occupying river channels,

general variations: the width of the water blocking building, the engineering muck, the newly repaired road and the like occupying the river channel is less than 1/3,

the larger the change: the width of the water blocking building, the engineering muck, the newly repaired road and the like occupying the river channel is more than 1/3 and less than 2/3,

the great change is that: the width of the river channel occupied by water-blocking buildings, engineering muck, newly-built roads and the like is more than 2/3;

the evaluation grading index of the self clogging degree of the building is as follows:

no change: the building does not have any clogging per se,

general variations: silt deposition and garbage blockage account for less than 10 percent of the height of the building,

the larger the change: silt deposition and garbage blockage account for more than 10 percent and less than 50 percent of the height of the building,

the great change is that: silt siltation and garbage blockage account for more than 50% of the height of the building;

the evaluation grading index of the building easy-to-block risk is as follows:

no change: the domestic garbage and the tree firewood floater are not arranged near the inlet, the building is far away from the mountain, the vegetation in the drainage basin is good, no geological breaking is caused, the geological disaster is not easy to happen,

general variations: a small amount of floating objects such as domestic garbage, trees, firewood and the like are arranged near the inlet, the proportion is less than 10 percent of the inlet space,

the larger the change: a certain amount of floating objects such as domestic garbage, trees, firewood and the like are arranged near the inlet, the proportion is more than 10 percent and less than 50 percent of the inlet space,

the great change is that: the quantity of domestic garbage, trees, firewood and other floating objects near the inlet is more than 50 percent of the inlet space, or the buildings are close to the mountain, the vegetation in the drainage basin is poor, the geology is broken, and the geological disasters are easy to occur;

the evaluation grading index of the socioeconomic development change is as follows:

no change: the left bank area of the water diversion project is a village,

general variations: the left bank area of the water transfer project is the periphery of the villages and towns,

the larger the change: the left bank area of the water transfer project is a village and a town,

the great change is that: the left bank area of the water transfer project is a city or the periphery of the city.

4. The method for evaluating flood control risk of water diversion engineering on left bank area of engineering area according to claim 1, wherein in step a2, the fuzzy mathematical comprehensive evaluation comprises:

A21. establishing a fuzzy relation matrix A of the factor discourse domain X and the comment discourse domain U:

x is the index of flood condition change evaluation corresponding to the evaluation unit, and U is the evaluation index grading corresponding to the evaluation unit, wherein: a is_ijRepresenting the ith factor X in the factor universe X_iCorresponding to the jth level u in the comment domain_jRelative degree of membership;

A22. determining the weight fuzzy vector W of the evaluation factor according to the entropy weight method₁,W₂,…,W_n) Wherein, in the step (A),

A23. and (3) realizing the synthesis of the weight vector W and the fuzzy relation matrix A through fuzzy synthesis operation to obtain a fuzzy comprehensive evaluation result B:

wherein:

for the fuzzy synthesis operator, the fuzzy synthesis operator adopts a weighted average operator

And (3) carrying out synthesis, namely:

；

A24. carrying out comprehensive evaluation, and taking the maximum value maxb of each component of B according to the maximum membership rule_jAnd taking the corresponding comment as a final comprehensive evaluation result.

5. The flood protection risk assessment method for the left bank area of the engineering area by the water transfer engineering according to claim 4, wherein the entropy weighting calculation step comprises:

a. standardizing data, standardizing data of each index, and giving n indexes X for flood condition change evaluation₁,X₂,…,X_nWherein X is_i＝{x_i1,…，x_ij，…,x_iLL is the number of samples, and the value normalized for each index data is Y₁，Y₂，…，Y_nWherein Y is_i＝{y_i1，…,y_ij,…,y_iLL, L is the number of samples, 1,2,. n, j is1, 2,. L,

b. calculating the information entropy of each index, and calculating the information entropy of a group of data according to the definition of the information entropy in the information theory

Wherein

If p is_ijWhen 0, then

c. Determining the weight of each index, and calculating the information entropy of each index to be E according to a calculation formula of the information entropy₁，E₂，…，E_nAnd calculating the weight of each index through the information entropy:

6. the flood control risk assessment method for the engineering area left bank area by the water transfer engineering according to claim 1, wherein in the step B, basin characteristic parameter information such as basin water collection area, river length, average specific gravity and the like above the cross section of each assessment unit is obtained by a method combining automatic extraction and manual correction by using an ArcGIS10.1 platform and a hydrological analysis module in a Spatial analysis tool Spatial analysis Tools according to 1:5 ten thousand DEM data, and is compared with the original design value of the water transfer engineering; and for the evaluation unit with obvious change of the characteristic value, analyzing the influence of the change of the conditions of the underlying surface of the drainage basin on the design flood by adopting the same calculation method as the original design.

7. The method for evaluating flood control risk of water diversion engineering on left bank area of engineering area according to claim 1, wherein in step C, the step of flood inundation simulation calculation comprises:

a. creating a distinguishing image for storing distinguishing flooding information, wherein the size of the area is the same as that of an evaluation unit (DEM), each pixel is consistent with the size of a DEM grid, and all values of the pixels are given to the elevation value of the flooding water level;

b. marking all grid points smaller than the water level elevation in the area to obtain a possibly submerged area; then, the isolated region is removed, and a set of all grid points with connected associated distribution, namely a flooding area, is found.

8. The method for assessing the flood control risk of the water transfer engineering on the left bank area of the engineering area according to claim 7, wherein the determination method of the flooding water level is to set a preset water level, calculate the filling amount by using a Surface analysis function Functional Surface in a 3D analysis extension module in ArcGIS, and obtain the flooding water level through trial calculation until the filling amount under the preset water level is close to the flood amount.

9. The method for assessing flood control risk of water diversion works in the left bank area of the project area according to claim 1, wherein in the step D, the assessment of economic loss and population impact consequences of flood comprises:

a. direct economic loss estimation:

and (3) field inundation loss:

wherein: l is_FarmlandFor economic loss of farmland (ten thousand yuan), O_{First industry}Is the total value (ten thousand yuan) of the first industry, A_{Agricultural land}For agricultural land area (km)²)，A_{Submerging farmland}To submerge the farmland area (km)²)，η_FarmlandThe farmland flood damage rate (the ratio of the value of farmland damage to the farmland property value before the disaster or in the normal year);

greenfield flooding loss:

L_greenbelt＝R_{Greenery patches remediation}×A_{Submerging green land}×η_Greenbelt

Wherein: l is_GreenbeltFor economic loss in greenland (ten thousand yuan), R_{Greenery patches remediation}Unit price for repairing greenbelt (ten thousand yuan/km)²)，A_{Submerging green land}To submerge a greenbelt area (km)²)，η_GreenbeltThe greenfield flood loss rate (the ratio of the value of greenfield loss to the value of the greenfield property before disaster or in the normal year);

the enterprise inundates and loses:

wherein: l is_EnterpriseFor economic loss of enterprise (ten thousand yuan), O_{Fixed assets of an enterprise}For an enterprise fixed asset Total value (ten thousand dollars), N_{Enterprise unit}Number of units of a business, A_{Flooding enterprises}To flood the enterprise area (km)²)，A_EnterpriseFor the land area (km) of the enterprise²)，η_{Industrial and mining enterprises}The flood loss rate of the enterprise (the ratio of the loss value of the enterprise to the property value of the enterprise before the disaster or in the normal year);

and (3) house submerging loss:

L_house＝R_{Affected premises}×A_{Submerged house}×η_House

Wherein: l is_HouseFor economic loss of house (ten thousand yuan), R_{Affected premises}For the unit price of the affected house (ten thousand yuan/km)²)，A_{Submerged house}To submerge a building area (km)²)，η_HouseThe house flood loss rate (the ratio of the house loss value to the house property value before the disaster or in the normal year);

b. flooding affects the population:

wherein: p_{Affecting the population}To influence population (people), P_{Total population}Is the total population (people) of the town (village), N_{Number of family}Is the number of families in town (village), A_{Submerged house}To submerge a building area (km)²)，A_{Every family residence}For each family residence area (km)²)。

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