CN116821268A - Urban inlet inflow process line determination method - Google Patents
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Abstract
The application provides a determining method of urban inlet inflow process lines, which is fit with actual urban runoff conditions and can effectively reduce errors of calculation results. Dividing the urban area into a plurality of subareas according to a road network, discharging the net rainfall from the rain gutters, and respectively calculating single rain gutters in the subareas; calculating urban surface runoff by adopting comprehensive runoff coefficient method to obtain runoff coefficient not greater than 1Representing the produced flow after rainfall is trapped and lost on the ground; rainfall is carried out on urban small areas, and the ground water flow state is slope flow and shallow water concentrated flow; the water collecting time is the sum of the two, the flow line is not more than 90m of slope flow, and the Manning dynamics method is adopted to calculate the surface runoff flow time; after the slope flow stops for 90m, shallow water concentrated flow with the water depth being more than 3cm appears at the moment, and a gully design flow inflow calculation formula is as follows:wherein: q is inlet flow of a rain inlet, and L/min; f is the average catchment area controlled by each inlet, m 2 。
Description
Technical Field
The application belongs to the field of urban rainfall inlet inflow calculation, and particularly relates to a method for determining urban inlet inflow process lines.
Background
At present, the important research targets of watershed hydrology are gradually turned to urban watershed, and a series of problems caused by the effect of increasing the surface runoff of water impermeability cause more and more views. Under the large background of rapid expansion of urban scale, urban building density is high, pavement hardening proportion is large, surface building is updated rapidly, and surface rainfall runoff is influenced by not only rainfall intensity and rainfall, but also complicated land utilization types of the surface.
High density, high occupancy hardened pavement and watertight construction are the main factors affecting urban surface runoff. Compared with the permeable pavement, the traditional impermeable pavement has the advantages of low cost, good durability and quick construction, so that the application range is wider. The manual river basin rainwater yield and confluence process of the traditional waterproof pavement with the high-density building is quite different from the traditional river basin yield and confluence process, and is difficult to explain in a traditional calculation mode. The slope confluence MODEL simulates the hydrological sub-process of the watershed from precipitation to the runoff and then to the slope confluence, the current urban ground confluence calculation method is mainly divided into a hydrologic method and a hydrodynamic method, and a plurality of MODELs such as TOP-MODEL, GBHM, SHE MODELs and the like are developed and established. Urban rainwater flow research generally utilizes coverage classification data and urban design scheme to divide areas to obtain a flow model suitable for subareas, and the flow model can be classified into a water surface flow model, a green water permeable layer flow model, a building and road water impermeable layer flow model and an open land depression filling water impermeable layer flow model according to types. In the research of the production converging process of the building and the road watertight area, students consider the rainwater at the top of the building as common rainfall to count into the surface rainwater runoff so as to neglect the real influence of the building on the rainfall, in fact, many building tops are processed so that the rainfall ponds directly enter the underground drainage system through the pipeline, the area of the building watertight layer is extremely high in the central urban area, the building density is high, the influence of the rainwater runoff by the building and the rainwater port is extremely high, and the larger error exists in the urban rainwater port inflow calculation result. In addition, in order to ensure smooth drainage without causing related problems, the rainwater ports in urban roads are extremely widely distributed, and the water collecting area is extremely small. The traditional inlet inflow calculation method has a plurality of assumption conditions, the uncertainty has a large influence, and the calculation result cannot be well fit with the actual situation.
Disclosure of Invention
Aiming at the technical problems, the application provides a determining method for urban inlet inflow process lines, which is attached to the actual urban runoff condition and can effectively reduce the error of the calculation result.
The specific technical scheme is as follows:
the urban areas have complex terrains and different rainfall loss causes. Greenbelts, plants, water surfaces, etc. can cause net interception and large rainfall losses caused by infiltration; other impervious surfaces in urban areas such as buildings, roads and other types of impervious layers due to depression loss; the surface rainwater evaporation mainly occurs after the rainfall is finished, and influences the early humidity of the next rainfall, so that the rainfall loss caused by evaporation can be avoided for single rainfall.
In the application, the fact that only a small number of surface flood flows from the inspection well into the pipe network and the rainfall loss caused by the seepage of the impervious ground is ignored is considered, most of rainwater enters the rainwater well through the rainwater inlets at two sides of the road, and the surface water is converged on the road and is discharged from the rainwater inlets which are slightly lower than the ground at two sides of the road. Therefore, the urban area is divided into subareas according to the main road network, the net rainfall is discharged from the rain gutters, and the single rain gutters in the subareas are respectively calculated, so that the systematic error generated by a model in calculation is reduced.
The single catchment area is extremely small, and in order to avoid the complex problems caused by more rainfall loss types and complex urban ground surface, and reduce the influence of the runoff difference of part of the gully catchment areas, the application calculates the urban surface runoff by adopting a comprehensive runoff coefficient method, so as to ensure that the runoff coefficient is not more than 1Representing the produced flow after rainfall is lost through ground interception.
Wherein:is a runoff coefficient, dimensionless; r is the runoff of a certain area in a certain period of time, and mm; p is precipitation in the same period of time in the area, and mm;
the outdoor drainage design standard (GB 50014-2021) (hereinafter referred to as standard) specifies the surface coverage class runoff coefficients as follows:
table 1 surface coverage runoff coefficient of species
The calculation formula of the comprehensive runoff coefficient is as follows:
wherein:is a comprehensive runoff coefficient; s is S i Covering various earth surfaces on regional topography; />And corresponding to the runoff coefficients for the corresponding ground types. The rainfall on the impervious layer of the building directly enters the drainage pipe network through the pipeline and does not account for the calculation of the confluence of the surface production, so that the comprehensive runoff coefficient is corrected according to the actual topography by considering that the building area does not participate in the weight ratio when the comprehensive runoff coefficient is calculated.
The calculation formula of the surface rain water flow intensity is as follows:
wherein: r is the net flow strength of the region, mm/min; i is regional rainfall intensity, mm/min.
The urban surface is different from a natural river basin, the difference of the surface runoff production process and the net rain runoff process is large, the water impermeable surface ratio of the urban area is high, the runoff coefficient is large, the runoff production and collection time is short, the water draining effect of the rain inlet is obvious, and the rain runoff is finished rapidly. The application aims at urban areas, and the application assumes that the rainfall is generated immediately after the rainfall, the flow generating time is ignored, and the water collecting time of the rainfall and the water withdrawal time after the rainfall is finished are considered. The standard has no specific calculation formula for the ground water collection time and the water withdrawal time, a suggested value range of the ground water collection time is provided, the requirement for limiting the water withdrawal time is met for ponding and waterlogging which have larger influence on densely populated, economical and road-dense areas, and the requirement for general rainfall is avoided. In order to solve the problem of uncertainty of the value of the water collection time, a formula is adopted for calculation.
For rainfall in urban small areas, the ground water flow state is mainly slope flow and shallow water concentrated flow. The water collection time is the sum of the two, the slope flow with the streamline not more than 90m is calculated by adopting a Manning dynamics method, and the calculation formula of the flow time is as follows:
wherein: t is t 1 Flow time, min; l (L) 1 The water collecting distance is m; n is corresponding toManning coefficient of 3cm and below water depth; s is the ground gradient; p (P) 2 The rainfall is 24 hours in a reproduction period of two years, and is mm.
After the slope flow stops for 90m, shallow water concentrated flow with water depth more than 3cm appears at the moment, and the flow time t 2 The calculation formula is as follows:
wherein: t is t 2 Flow time, min; l (L) 2 The water collecting distance is m; k is the surface runoff coefficient of shallow water concentrated flow;
the calculation methods such as the isochrone method, the linear reservoir method and the nonlinear reservoir method have good effect in a natural drainage basin, the surface runoff process of the drainage basin is different from the converging system, and the actual water converging area of a single drainage basin is far less than 2km 2 The standard prescribes that the design flow of the rainwater pipe channel is calculated according to an inference formula method at the moment, so that the application calculates the inflow process line of the design flow of the urban rain inlet by adopting the inference formula method after the correction coefficient, and the influence of the non-uniformity of the rainfall on a small water collecting area is small, so that the rainfall distribution can be considered to be uniform.
The design flow inflow calculation formula of the rain inlet is as follows:
wherein: q is inlet flow of a rain inlet, and L/min; f is the average catchment area controlled by each inlet, m 2 If the generalizable selection cannot be determined; the rest are the same as above.
For the determination of the F control paving area, the application considers that a reduction coefficient beta is multiplied on the basis of the control area to represent the actual condition that the rainfall on the roof of the watertight building does not sink into the rain inlet, and beta is related to the building density.
The related norms have no specific deep standard on the impermeable surface in the urban area rainfall runoff, the rainfall on the impermeable surface at the top of the building is eliminated by further subdividing the rainfall on the urban high-density impermeable surface, and the urban rainfall runoff and the inlet of the rain water inflow calculation result is more reliable.
Drawings
FIG. 1 is a flow chart of a computing method according to the present application;
FIG. 2 is a digital elevation model of Wu Hou Ou of the present application;
FIG. 3 is a graph of the grade of the terrain of the present application for Wu Hou Ou;
FIG. 4 is a diagram of the type of surface utilization of the Wu Hou Ou of the present application;
fig. 5 is a plot of the intensity of rainfall (2 years recurring period, rainfall duration 120 minutes) according to the present application.
Detailed Description
Specific embodiments of the present application are described with reference to the examples.
In this embodiment, for example, the process of Wu Hou Ou in Chengdu is shown in FIG. 1:
the city Wu Houou is slightly inclined from northwest to southeast, has flat topography, takes a butterfly shape, and belongs to subtropical humid monsoon climate in the interior, and is hotter in summer and rainy and storm-free. The total area of the land is 75.36km 2 Wu Houou governs 15 streets.
The application calculates the related parameters of the urban land surface by means of ARC GIS software and introduces urban yield convergence calculation method and flow. The Wuhou district is located between 103 degrees 56 '45' -104 degrees 05 '33', 30 degrees 34 '31' -30 degrees 39 '49' of north latitude, ASTER GDEM M resolution digital elevation data are downloaded and obtained in a geospatial data cloud, DEM is loaded by using GIS and embedded and fused, the projection method adopts Mokatuo projection, a calculated projection coordinate system is WGS_1984_UTM_Zone_48N, the calculated projection coordinate system is shown in figure 2 after cutting, gradient calculation is carried out on the terrain, and the average gradient of the Wu Houou surface is 3.73% as shown in figure 3. The construction, road and green land data are projected to wgs_1984_utm_zone_48n in a unified manner, and other land coverage utilization data such as water systems are ignored, and the regional topography is shown in fig. 4. The total area of the building is calculated to be about 24.4km 2 The occupied ratio reaches 32.4 percent, and the green area is about 1.91km 2 The ratio is 2.5%.
Other impervious surfaces have no specific data, 70% of the other surfaces except for buildings and green land are generalized to asphalt and concrete pavement, and the other 30% are generalized to stone paved pavement. The area surface area is as follows:
TABLE 2 Chengdu Wu Hou Ou surface type area Table
| Ground type | Building construction | Asphalt and concrete pavement | Block stone road surface | Greenbelt |
| Area (km) 2 ) | 24.4 | 34.34 | 14.71 | 1.91 |
The integrated runoff coefficient is calculated by equation 2 as follows:
the formula of the storm intensity in the central urban area of the Chengdu city is as follows:
wherein: i is the average rainfall intensity in time period, mm/min; p is the period of reproduction, year; t is rainfall duration, min; taking the period of reproduction of 2 years, and the rainfall duration of 120min, and calculating i to be 0.468mm/min. The area average flow strength is then r=0.79×0.468=0.370 mm/min.
The rainfall adopts the Chicago synthetic rainfall process line method, as shown in figure 5, the peak ratio r 1 Substituting the rainfall intensity of the rainfall into relevant parameters to calculate to obtain an instantaneous rainfall intensity table, wherein the instantaneous rainfall intensity table is as follows:
TABLE 3 rainfall instantaneous intensity meter
The actual instantaneous yield strength of rainfall obtained from the above table is shown below:
TABLE 4 rainfall instantaneous flow intensity meter
The quantity and the position of the rain water inlet in the area have no accurate data, and the paving area is controlled to be 200m 2 The reduction coefficient β is calculated as follows:
the actual value F is calculated to be =0.67×200=134 m 2 。
The average control area of a single rain inlet is extremely small, and only slope flow occurs on the ground surface, so the rainfall water collection time is the flow time of the slope flow, the rainfall duration is changed into 24 hours, and the other conditions and the mould are adoptedThe rainfall is similar to be consistent, and the rainfall P in the period of reproduction in two years 2 45.0869mm; urban rainfall runoff flows on the surfaces of asphalt and concrete, and the Manning coefficient n is 0.015; the ground slope S is 3.73%; the water collecting distance is set to be 90m, and t is calculated by the method of 4 1 3.86min, and actually 4min.
The calculation results of the inlet design flow and the inlet inflow are as follows:
table 5 inlet for stom water inflow rain gauge
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (2)
1. A method for determining inflow process line of a gully in an urban area is characterized by comprising the following steps:
dividing the urban area into a plurality of subareas according to a road network, discharging the net rainfall from the rain gutters, and respectively calculating single rain gutters in the subareas;
calculating urban surface runoff by adopting comprehensive runoff coefficient method to obtain runoff coefficient not greater than 1Representing the produced flow after rainfall is trapped and lost on the ground;
wherein:is a runoff coefficient, dimensionless; r is the runoff of a certain area in a certain period of time, and mm; p is precipitation in the same period of time in the area, and mm;
the calculation formula of the comprehensive runoff coefficient is as follows:
wherein:is a comprehensive runoff coefficient; s is S i Covering various earth surfaces on regional topography; />Corresponding runoff coefficients for the corresponding ground types;
the calculation formula of the surface rain water flow intensity is as follows:
wherein: r is the net flow strength of the region, mm/min; i is regional rainfall intensity, mm/min;
rainfall is carried out on urban small areas, and the ground water flow state is slope flow and shallow water concentrated flow; the water collection time is the sum of the two, the slope flow with the streamline not more than 90m is calculated by adopting a Manning dynamics method, and the calculation formula of the flow time is as follows:
wherein: t is t 1 Flow time, min; l (L) 1 The water collecting distance is m; n is a water depth corresponding to 3cm and belowManning coefficients; s is the ground gradient; p (P) 2 The rainfall is 24 hours in a two-year-meeting reproduction period, and is mm;
after the slope flow stops for 90m, shallow water concentrated flow with water depth more than 3cm appears at the moment, and the flow time t 2 The calculation formula is as follows:
wherein: t is t 2 Flow time, min; l (L) 2 The water collecting distance is m; k is the surface runoff coefficient of shallow water concentrated flow;
the design flow inflow calculation formula of the rain inlet is as follows:
wherein: q is inlet flow of a rain inlet, and L/min; f is the average catchment area controlled by each inlet, m 2 If the generalizable selection cannot be determined; the rest are the same as above.
2. A method of determining a process line for inflow of urban area gullies according to claim 1, wherein the determination of the F-controlled paving area is multiplied by a reduction factor β to indicate the actual condition that the rain drops from the roof of the watertight building do not enter the gullies, β being related to the building density.
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