CN104268409A - Calculation method for ground surface water collection time - Google Patents

Abstract

The invention discloses a calculation method of ground surface water collection time, and belongs to the calculation method of the ground surface water collection time in the fields of municipal water supply and drainage engineering, water conservancy projects as well as soil and water conservation projects. The calculation method comprises the following steps of: 1, dividing N rainwater collection regions based on a DEM map of an area; 2, calculating and selecting a ground average slope Si and the maximum water collection distance Li (m) of a rainwater collection region i; (3) dividing flow states of flow lines of the rainwater collection regions; 4, selecting ground surface design parameters; 5, calculating the ground surface water collection time. The calculation method is clear in physical significance, clear and systemic in calculation step and fast in calculation speed, is easy to obtain the parameters, fully considers influences from different areas, different landforms, land cover and surface roughness to the ground surface water collection time, and provides a scheme under a complex condition. The calculation method can be used for design and planning of outdoor rainwater pipe systems, flood control projects as well as soil and water conservation projects, assessment on an existing project, and planning and design of reconstruction and expansion schemes.

Description

The computing method of a kind of ground inlet time

Technical field

The present invention relates to the computing method of ground inlet time in a kind of outdoor rain water pipe canal system system, flood control works and erosion and torrent control works design, for the computing method in municipal water supply and sewage work, hydraulic engineering and erosion and torrent control works design.

Background technology

In recent years, domestic a lot of city takes place frequently urban waterlogging Disaster Event, and after suffering that heavy rain attacks flood season, urban rainwater drainage system is paralysed, the method for designing of China's Storm Sewer System system and flood control works is faced with serious test, and design standards and method need revision further, improve and carry mark.Research based on the relevant method for designing of municipal drainage system and flood control works is the research emphasis in this field always, as patent of invention " a kind of computing method of the water catchment area rainfall depth of accumulated water based on DEM ", and application number 201210420043.6; Patent of invention " urban design rainstorm calculation method ", application number 201210190613.7; Patent of invention " a kind of LID type storm-collector and design and calculation method thereof ", application number 201310555523.8.

" Code for design of outdoor sewerage engineering " (GB50014-2006,2014 editions) comprise the revision of Storm Sewer System design method: be less than 2km for water catchment area ², adopt push pull azobenzene compounds to calculate design flow of storm drain; When water catchment area is more than 2km ²time, should consider that rainfall is at the unevenness of spatial and temporal distributions and pipe network Process of Confluence, adopt mathematical model method to calculate design flow of storm drain; Improve the Designed recurrence period standard of Storm Sewer System; Cancel reduction coefficient m etc.

But existing specification, to the regulation of ground inlet time, does not but still change, that is: according to domestic data, the data that ground inlet time adopts, scarcely as calculated, determine by experience., rainfall intensity close in ground even, floor type is more or less the same, ground distance of catchmenting is the principal element determining inlet time length; The catchment zone of reasonableness of distance of ground is 50m ~ 150m, and the inlet time of employing is 5min ~ 15min.

When water catchment area reaches 2km ²time, according to square and 90 degree fan-shaped charge for remittance shapes calculating, streamline can reach 2000m and 1596m, creates certain conflicting with specification provision " ground catchment the zone of reasonableness of distance be 50m ~ 150m ".Therefore, when water catchment area is comparatively large, when distance of catchmenting is more than 150m, specification does not provide the computing method of a rational ground inlet time, and selection inlet time 5min ~ 15min blindly, can cause the mistake of push pull azobenzene compounds to use.In addition, when distance is catchmented for 50m ~ 150m in ground, deviser has no basis for the selection of the ground inlet time recommended, these computing method of not being correlated with mainly due to China.

Summary of the invention

The object of the invention is to provide a kind of to calculate reliably, precision is higher, is conducive to the ground inlet time computing method that project planner uses, and solves blank and the probabilistic technical matters of value of China's ground inlet time computing method.

For solving the problems of the technologies described above, the present invention adopts following technical proposals to realize, and comprises the following steps:

Step 1, to scheme based on the DEM in region, divide N number of rainwater watershed; For rainwater watershed i, its water catchment area A _i; I=1,2 ... N, A _i<2km ², select the 24 hourly rainfall depth P that design area is met for 2 years, unit mm, determines to grow the streamline that catchments most;

Step 2, calculate and choose the ground mean inclination S of rainwater watershed i _i, the maximum distance L that catchments _i(m); Wherein the selection gist of maximum distance of catchmenting has landform, the gradient, watershed shape, generally should be not more than 1600m, maximumly must not be greater than 2000m;

The division of fluidised form on step 3, rainwater watershed streamline; Work as L _i≤ 90m, then X on streamline _iplace is sheet stream; Work as L _i>90m, then X on streamline _iplace is sheet stream, 0≤X _i<90; Work as L _i>90m, then X on streamline _ilocate as shallow water concentrates stream, 90≤X _i<L _i;

Choosing of step 4, earth's surface design parameter; Work as L _iduring≤90m, according to earth's surface coverage condition, choose the earth's surface Manning coefficient n that sheet stream occurs _i; Work as L _iduring >90m, choose the earth's surface Manning coefficient n that sheet stream occurs respectively _iearth's surface, the region situation COEFFICIENT K of stream is concentrated with generation shallow water _i;

Step 5, calculating ground inlet time t ₁=t ₁₁+ t ₁₂(min);

Work as L _i≤ 90m,

$t_1=t_{11}+t_{12}=\frac{5.476{\left(n_i{L}_i\right)}^{0.8}}{P^{0.5}{S_i}^{0.4}}$

Work as L _i>90m,

$t_1=t_{11}+t_{12}=\frac{5.476{\left(90n_i\right)}^{0.8}}{P^{0.5}{S_i}^{0.4}}+\frac{0.0547(L_i-90)}{K_i{S_i}^{0.5}}$

In formula: parameter P is 24 hourly rainfall depths of meeting for 2 years in design area, mm; Parameter S _ifor ground mean inclination; Parameter L _imaximum distance of catchmenting, m; Parameter n _ifor there is the earth's surface Manning coefficient of sheet stream; Parameter K _iearth's surface, the region situation coefficient of stream is concentrated for there is shallow water;

During design planning for outdoor rain water pipe canal system system, flood control works and erosion and torrent control works, parameter S _i, n _iand K _iselection should consider in 20 year project period least favorable situation.

Concrete:

1, in described step 1, the selection of P with reference to local data or National Meteorological Bureau's data, if data disappearance, should can consider the data selecting close city.

2, in described step 1, if the landform of rainwater watershed i, ground mulching, roughness of ground surface are very complicated, then consider on the i of region, select different streamline analyses of catchmenting, to determine the ground inlet time in least favorable situation.

3, in described step 2, when topographic features is more complicated, parameter S _ifor the weighted mean value of surface slope, area weighted average should be adopted;

4, in described step 4, when earth's surface coverage condition is more complicated, parameter n _i, K _ifor weighted mean value, area weighted average should be adopted.

5, in described step 5, for the flood control system that there is open channel, ground inlet time t ₁should comprise before entering storm-water system, the flowing time t of rainwater in open channel ₁₃;

$t_{13}=\frac{L^{\&prime;}}{V}=\frac{L^{\&prime;}}{\frac{R^{\frac{2}{3}}{S}^{\&prime;\frac{1}{2}}}{n^{\&prime;}}}=\frac{n^{\&prime;}{L}^{\&prime;}}{R^{\frac{2}{3}}{S}^{\&prime;\frac{1}{2}}}$

Above formula uses Manning formula to estimate mean flow rate, calculates by flowing full; In formula, V is mean flow rate, m/s; R is hydraulic radius, m; S' is the plane gradient of open channel; L' is the flow distance of rainwater in open channel, m; N' is the Manning's roughness coefficient in open channel.

Beneficial effect, owing to have employed such scheme, computing method explicit physical meaning of the present invention, calculation procedure system orderliness, computing velocity is fast, calculating parameter easily obtains, and has taken into full account that different regions, different terrain landforms, ground mulching and roughness of ground surface are on the impact of ground inlet time, and has proposed the solution in complicated landform, ground mulching and roughness of ground surface situation.

Computing method of the present invention may be used for the design planning of outdoor rain water pipe canal system system, flood control works and erosion and torrent control works, assess existing engineering, and the planning and design of modified threshold.Solve the blank that distance of catchmenting is selected more than ground inlet time in specification during 150m, and catchment apart from the two problems that has no basis for the selection of ground inlet time during 50m ~ 150m in ground simultaneously.

Result of calculation of the present invention can realize visual based on GIS, the ground inlet time result calculated marks in each geographical grid with the form of landform, uses different colors to play up, for the situation in Analysis of Complex region.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of ground of the present invention inlet time computing method.

Fig. 2 is that the present invention catchments apart from the result of calculation of the ground inlet time in situation to Harbin City's difference.

Fig. 3 is that the present invention catchments apart from the result of calculation of the ground inlet time in situation to Shanghai City difference.

Embodiment

Below in conjunction with embodiment, the specific embodiment of the present invention is described in further detail, specific embodiment of the invention step and effect are described.Following examples for illustration of the present invention, but are not used for limiting the scope of the invention.

Comprise the following steps:

Step 1, to scheme based on the DEM in region, divide N number of rainwater watershed; For rainwater watershed i, its water catchment area A _i; I=1,2 ... N, A _i<2km ², select the 24 hourly rainfall depth P that design area is met for 2 years, unit mm, determines to grow the streamline that catchments most;

Step 2, calculate and choose the ground mean inclination S of rainwater watershed i _i, the maximum distance L that catchments _i(m); Wherein the selection gist of maximum distance of catchmenting has landform, the gradient, watershed shape, generally should be not more than 1600m, maximumly must not be greater than 2000m;

The division of fluidised form on step 3, rainwater watershed streamline; Work as L _i≤ 90m, then X on streamline _iplace is sheet stream; Work as L _i>90m, then X on streamline _iplace is sheet stream, 0≤X _i<90; Work as L _i>90m, then X on streamline _ilocate as shallow water concentrates stream, 90≤X _i<L _i;

Choosing of step 4, earth's surface design parameter; Work as L _iduring≤90m, according to earth's surface coverage condition, choose the earth's surface Manning coefficient n that sheet stream occurs _i; Work as L _iduring >90m, choose the earth's surface Manning coefficient n that sheet stream occurs respectively _iearth's surface, the region situation COEFFICIENT K of stream is concentrated with generation shallow water _i;

Step 5, calculating ground inlet time t ₁=t ₁₁+ t ₁₂(min);

Work as L _i≤ 90m,

$t_1=t_{11}+t_{12}=\frac{5.476{\left(n_i{L}_i\right)}^{0.8}}{P^{0.5}{S_i}^{0.4}}$

Work as L _i>90m,

$t_1=t_{11}+t_{12}=\frac{5.476{\left(90n_i\right)}^{0.8}}{P^{0.5}{S_i}^{0.4}}+\frac{0.0547(L_i-90)}{K_i{S_i}^{0.5}}$

In formula: P is 24 hourly rainfall depths of meeting for 2 years in design area, mm; S _ifor ground mean inclination; L _imaximum distance of catchmenting, m; n _ifor there is the earth's surface Manning coefficient of sheet stream; K _iearth's surface, the region situation coefficient of stream is concentrated for there is shallow water.

Concrete:

1, the selection of design parameter; The selection of P with reference to local data or National Meteorological Bureau's data, if data disappearance, should can consider the data selecting close city; When topographic features is more complicated, S _ifor the weighted mean value of surface slope; When earth's surface coverage condition is more complicated, n _i, K _ifor weighted mean value; Time normal, adopt area weighted average;

If the landform of 2 rainwater watershed i, ground mulching, roughness of ground surface are very complicated, then can consider to select different streamline analyses of catchmenting on the i of region, to determine the ground inlet time in least favorable situation;

3, when for outdoor rain water pipe canal system system or the design planning of flood control works, S _i, n _iand K _ithe selection of parameter should consider the least favorable situation in 20 year project period;

4, for the flood control system that there is open channel, ground inlet time t ₁should comprise before entering storm-water system, the flowing time t of rainwater in open channel ₁₃;

$t_{13}=\frac{L^{\&prime;}}{V}=\frac{L^{\&prime;}}{\frac{R^{\frac{2}{3}}{S}^{\&prime;\frac{1}{2}}}{n^{\&prime;}}}=\frac{n^{\&prime;}{L}^{\&prime;}}{R^{\frac{2}{3}}{S}^{\&prime;\frac{1}{2}}}$

Above formula uses Manning formula to estimate mean flow rate, calculates by flowing full; In formula, V is mean flow rate, m/s; R is hydraulic radius, m; S' is the plane gradient of open channel; L' is the flow distance of rainwater in open channel, m; N' is the Manning's roughness coefficient in open channel.

Adopt above-mentioned computing method to China Harbin and Shanghai, different ground mulching, difference catchment distance situation under ground inlet time calculate.

The 24h rainfall amount that Shanghai and 2 years one, Harbin are met is respectively 100 and 59mm.Suppose that water catchment area can reach critical value 2km ²time, gradient computer capacity is 0.001 ~ 0.5, and calculate according to 90 degree of fan-shaped charge for remittance shapes, distance of catchmenting can reach 1596m.During sheet stream, Manning coefficient gets 0.011 and 0.15 two kind of situation respectively; When shallow water is concentrated and flowed, consider by ground paving is thorough, K _i=20.33.

Fig. 2 with Fig. 3 is respectively the result of calculation of the ground inlet time in Harbin City's distance situation of catchmenting different from Shanghai City.As can be seen from the figure, concerning same city, earth's surface mean inclination is larger, and ground inlet time is shorter; Earth's surface Manning coefficient is larger, and ground inlet time is longer; The 24h rainfall amount of meeting for 2 years one is larger, and ground inlet time is shorter.It can thus be appreciated that computing method of the present invention, well consider landform, ground mulching, roughness of ground surface, different cities rainstorm pattern to the impact of ground inlet time.

Catchmenting (in figure rectangular box) in distance range at 50-150m, the invention provides the selection gist of ground inlet time; When distance of catchmenting is more than 150m, the invention provides the computing reference value of ground inlet time.In addition, " Code for design of outdoor sewerage engineering " (GB50014-2006,2014 editions) the regulation of provision " the catchment zone of reasonableness of distance of ground is 50m ~ 150m, and employing inlet time is 5min ~ 15min ", from the present embodiment, also reflected the uncertainty of this provision.

As can be seen from above-described embodiment, the present invention is under different terrain, ground mulching, roughness of ground surface, urban storm type cases, provide the computing method of a kind of ground inlet time, and solution when proposing complicated landform, ground mulching and roughness of ground surface.

It should be pointed out that for project planner, under the prerequisite not departing from the technology of the present invention principle, can make some improvement or distortion, these improve or distortion also should be considered as protection scope of the present invention.

Claims (6)

1. computing method for ground inlet time, is characterized in that: comprise the steps:

Step 1, to scheme based on the DEM in region, divide N number of rainwater watershed; For rainwater watershed i, its water catchment area A _i; I=1,2 ... N, A _i<2km ², select the 24 hourly rainfall depth P that design area is met for 2 years, unit mm, determines to grow the streamline that catchments most;

Step 2, calculate and choose the ground mean inclination S of rainwater watershed i _i, the maximum distance L that catchments _i(m); Wherein the selection gist of maximum distance of catchmenting has landform, the gradient, watershed shape, generally should be not more than 1600m, maximumly must not be greater than 2000m;

The division of fluidised form on step 3, rainwater watershed streamline; Work as L _i≤ 90m, then X on streamline _iplace is sheet stream; Work as L _i>90m, then X on streamline _iplace is sheet stream, 0≤X _i<90; Work as L _i>90m, then X on streamline _ilocate as shallow water concentrates stream, 90≤X _i<L _i;

Choosing of step 4, earth's surface design parameter; Work as L _iduring≤90m, according to earth's surface coverage condition, choose the earth's surface Manning coefficient n that sheet stream occurs _i; Work as L _iduring >90m, choose the earth's surface Manning coefficient n that sheet stream occurs respectively _iearth's surface, the region situation COEFFICIENT K of stream is concentrated with generation shallow water _i;

Step 5, calculating ground inlet time t ₁=t ₁₁+ t ₁₂(min);

Work as L _i≤ 90m,

$t_1=t_{11}+t_{12}=\frac{5.475{\left(n_i{L}_i\right)}^{0.8}}{P^{0.5}{S_i}^{0.4}}$

Work as L _i>90m,

$t_1=t_{11}+t_{12}=\frac{5.476{\left(90n_i\right)}^{0.8}}{P^{0.5}{S_i}^{0.4}}+\frac{0.0547(L_i-90)}{K_i{S_i}^{0.5}}$

In formula: parameter P is 24 hourly rainfall depths of meeting for 2 years in design area, mm; Parameter S _ifor ground mean inclination; Parameter L _imaximum distance of catchmenting, m; Parameter n _ifor there is the earth's surface Manning coefficient of sheet stream; Parameter K _iearth's surface, the region situation coefficient of stream is concentrated for there is shallow water;

During design planning for outdoor rain water pipe canal system system, flood control works and erosion and torrent control works, parameter S _i, n _iand K _iselection should consider in 20 year project period least favorable situation.

2. as right 1 require as described in the computing method of a kind of ground inlet time, it is characterized in that, in described step 1, the selection of parameter P is with reference to local data or National Meteorological Bureau's data, if data disappearance, or considers the data selecting close city.

3. as right 1 require as described in the computing method of a kind of ground inlet time, it is characterized in that, in described step 1, if the landform of rainwater watershed i, ground mulching, roughness of ground surface are very complicated, then consider on the i of region, select different streamline analyses of catchmenting, to determine the ground inlet time in least favorable situation.

4. as right 1 require as described in the computing method of a kind of ground inlet time, it is characterized in that, in described step 2, when topographic features is more complicated, parameter S _ifor the weighted mean value of surface slope, area weighted average should be adopted.

5. as right 1 require as described in the computing method of a kind of ground inlet time, it is characterized in that, in described step 4, when earth's surface coverage condition is more complicated, parameter n _i, K _ifor weighted mean value, area weighted average should be adopted.

6. as right 1 require as described in the computing method of a kind of ground inlet time, it is characterized in that, in described step 5, for the flood control system that there is open channel, before ground inlet time t1 should comprise and enters storm-water system, the flowing time t13 of rainwater in open channel;

$t_{13}=\frac{L^{\&prime;}}{V}=\frac{L^{\&prime;}}{\frac{R^{\frac{2}{3}}{S}^{\&prime;\frac{1}{2}}}{n^{\&prime;}}}=\frac{n^{\&prime;}{L}^{\&prime;}}{R^{\frac{2}{3}}{S}^{\&prime;\frac{1}{2}}}$

Above formula uses Manning formula to estimate mean flow rate, calculates by flowing full.In formula, V is mean flow rate, m/s; R is hydraulic radius, m; S' is the plane gradient of open channel; L' is the flow distance of rainwater in open channel, m; N' is the Manning's roughness coefficient in open channel.