Urban waterlogging simulation method and system based on terrain catchment unit

Abstract

The application relates to a city waterlogging simulation method and system based on a terrain catchment unit, wherein the city waterlogging simulation method comprises the following steps: acquiring digital elevation model data of a target region; based on the digital elevation model data, terrain in the target region is divided into at least one closed catchment unit; for each catchment unit, an elevation-accumulated water volume index table of the catchment unit is generated in advance; rainfall time series data are acquired, and the accumulated water change process of each catchment unit is dynamically simulated based on the elevation-accumulated water volume index table, and a waterlogging simulation result is output; through the division of the terrain into the catchment unit with clear physical meaning and the adoption of the simplified linear water level-capacity relationship to describe the accumulated water behavior, the calculation complexity is greatly reduced while the natural catchment and water recession physical laws are reserved, and the compatibility of high-precision simulation and second-level response is realized.

Description

Technical Field

[0001] This invention relates to the field of urban flooding simulation technology, and specifically to an urban flooding simulation method and system based on topographic catchment units. Background Technology

[0002] Traditional municipal drainage systems, designed primarily for drainage, often struggle to cope with extreme rainfall far exceeding their capacity.

[0003] Urban stormwater flooding models are crucial tools for scientifically understanding flooding risks, accurately assessing drainage system effectiveness, and supporting emergency decision-making; however, existing mainstream flooding simulation methods mainly suffer from the following two types of technical bottlenecks: One type is the physical mechanism model represented by SWMM, MIKE URBAN, and InfoWorks ICM. It adopts a numerical method that couples a one-dimensional pipeline network with a two-dimensional surface. It has a clear physical mechanism, but it has extremely strict data requirements, takes a long time to calculate, and has complex parameter calibration, making it difficult to support the real-time early warning requirements with a second-level response.

[0004] Another type is the simplified model represented by cellular automata, which simulates water diffusion based on GIS platform and simplified hydraulic rules. It has a faster calculation speed, but its physical mechanism is weaker and the simulation results are not refined enough, making it difficult to accurately reflect the complete dynamic process of water accumulation from occurrence to receding.

[0005] Therefore, how to significantly improve the computational speed of urban flooding simulation while ensuring the authenticity of the physical mechanisms, so as to meet the needs of real-time early warning and high-frequency operational use, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention addresses the technical shortcomings of existing urban flooding simulation methods, which struggle to balance the realism of physical mechanisms with computational speed. It provides an urban flooding simulation method and system based on topographic catchment units, which can significantly improve computational efficiency and meet the needs of real-time early warning while ensuring that the evolution of water accumulation conforms to the hydrodynamic laws of natural terrain.

[0007] To achieve the above objectives, this invention provides a method for simulating urban flooding based on topographic catchment units, comprising the following steps: Obtain digital elevation model data for the target area; Based on the digital elevation model data, the terrain within the target area is divided into at least one closed catchment unit. For each of the aforementioned water catchment units, an elevation-water accumulation volume index table for that water catchment unit is generated in advance; Acquire rainfall time series data, and dynamically simulate the water accumulation change process of each catchment unit based on the elevation-water accumulation volume index table, and output the waterlogging simulation results.

[0008] By adopting this technical solution, the catchment unit is used as the basic calculation unit for urban flooding simulation. This changes the traditional approach of using grids or drainage blocks as single calculation units. Before the simulation calculation, an independent elevation-water volume index table is pre-established for each catchment unit. This simplifies the conversion between water volume and water level during the simulation process from real-time integral calculation to table lookup. While retaining the dominant influence of topography on the water accumulation process, the amount of computation required for each calculation period is significantly reduced. This enables the physical mechanism-based urban flooding simulation to meet the computational speed requirements of real-time operational use.

[0009] Furthermore, the target area is pre-divided into multiple drainage blocks, each of which contains at least one water collection unit.

[0010] By adopting this technical solution, the drainage block, as a hydraulically independent superior unit, has its boundaries corresponding to the urban drainage network system and administrative jurisdiction areas. This allows the results of urban flooding simulation to be aggregated, statistically analyzed, and output according to the drainage block, facilitating integration with the existing urban flood control management system and enabling the zoned release of early warning information and the zoned dispatch of emergency resources.

[0011] Furthermore, the catchment unit is an independent water-collecting basin corresponding to a topographic depression, and each catchment unit has at least the lowest point elevation within the unit and the lowest point elevation on its boundary ridge line as characteristic parameters.

[0012] By adopting this technical solution, the lowest point elevation is the starting point of water accumulation and also the water level benchmark for the water level-capacity relationship; the lowest point elevation on the boundary ridge is the upper limit of independent water storage in the catchment unit and also the threshold for the initiation of overflow; these two characteristic parameters transform the abstract topographic depression into a mathematical model unit with clear boundaries and quantitative characteristics, providing a physical basis and computational foundation for subsequently establishing the functional relationship between water level and water storage capacity.

[0013] Furthermore, the water level of each of the aforementioned water collection units h With water storage capacity V The following relationship exists between them: V ( h )= A 0* ( h - h min ), h min ≤ h ≤ h ridge in, h min This is the elevation of the lowest point in the catchment area. h ridge This is the elevation of the lowest point on the ridge line of the catchment unit's boundary. A 0 represents the baseline area parameter for this catchment unit.

[0014] By adopting this technical solution A Geometrically, 0 can be understood as the average cross-sectional area of ​​the catchment unit in the vertical projection direction. Its value can be predetermined or obtained through topographic data. Compared with the nonlinear surface fitting model, this linear model significantly reduces the complexity of parameter calibration and the consumption of computational resources, while retaining the dominant control of topographic elevation difference on water accumulation capacity. This makes the simulation method based on physical mechanism have computational efficiency comparable to the simplified model.

[0015] Furthermore, the elevation-water volume index table is a lookup table generated by integrating and summing the water catchment units as the basic calculation units, and is used to record the water volume corresponding to different water levels.

[0016] By adopting this technical solution, the binding relationship between the elevation-water accumulation volume index table and the water catchment unit is clarified—the index table uses the water catchment unit as the integration basis, rather than the drainage block or the entire target area as the basis; the index table based on the water catchment unit corresponds to the water accumulation volume and water level relationship within a single topographic depression, preserving the natural dividing effect of the topographic unit boundary on the water accumulation process, and avoiding the physical distortion caused by the global integration forcibly merging multiple independent depressions into a single water accumulation body.

[0017] Furthermore, it also includes: An elevation-water depth index table is pre-generated, which stores the effective elevation value of each grid pixel. The effective elevation value is the ground elevation value of the grid pixel. For the grid pixel where the building is located, its effective elevation value is the sum of the ground elevation value and the water level at the building threshold. During the simulation, the water depth of any grid pixel is obtained by looking up the table based on the given water level and the elevation-water depth index table.

[0018] By adopting this technical solution, the effective elevation value of each grid pixel is stored in advance, simplifying the calculation of water depth from a process of real-time reading of the digital elevation model, comparison with the water level, and calculation of the difference to a single-step table lookup operation of water level minus effective elevation value. At the same time, the correction rules for the flooding height of building thresholds are clearly defined: for the grid where the building is located, its effective elevation value is the sum of the ground elevation and the threshold height. This correction enables the model to simulate the physical process of rainwater overflowing the building threshold before entering the building and accumulating water inside. This solves the problem of premature water accumulation inside buildings caused by conventional digital elevation models treating the building surface and the ground as equal.

[0019] Furthermore, the water accumulation process includes a water accumulation increase phase and a water accumulation receding phase; During the water accumulation phase, when the water level of a catchment unit reaches the lowest point elevation on its boundary ridge, the excess water overflows into adjacent catchment units. During the receding phase of floodwaters, when the water level within a catchment unit drops below its internal topographic ridgeline, the previously connected flooded area is divided into multiple independent catchment units.

[0020] By adopting this technical solution, during the water accumulation phase, the only criterion for overflow is that the water level reaches the lowest point of the boundary ridge, and the overflow direction is from the high-water-level unit to the adjacent low-water-level unit. During the water receding phase, the only criterion for regional segmentation is that the water level drops below the internal topographic ridge. This two-stage model and the overflow / segmentation rules enable the simulation process to achieve a high degree of consistency with the natural hydrological and physical processes at the mathematical level. In particular, it realizes the objective hydrological law of water accumulation-receding asymmetry for the first time in a simplified model, avoiding the systematic biases such as excessively rapid water level drop and incorrect shrinkage paths of water accumulation areas that occur in traditional symmetrical models during the receding phase.

[0021] Furthermore, during the water receding phase, the water receding process of a single catchment unit is simulated using the following model: h ( t )= h 0* e －αt + h residual in, h ( t )for t The depth of the water at any given time h 0 represents the initial water depth. a This is the coefficient for the rate of water discharge. h residual This represents the residual water depth.

[0022] By adopting this technical solution, the complex multi-physics coupled drainage process is simplified into a two-parameter exponential function. While ensuring that the overall shape of the drainage curve conforms to the measured law, the complexity of drainage calculation and the difficulty of parameter calibration are greatly reduced, making it suitable for high-frequency rolling calculation scenarios in operational systems.

[0023] The present invention also provides a system for implementing an urban flooding simulation method based on topographic catchment units, comprising: The data acquisition module is used to acquire digital elevation model data and rainfall time series data for the target area; The preprocessing module is used to divide the terrain within the target area into at least one closed catchment unit based on the digital elevation model data, and to pre-generate an elevation-water volume index table for each catchment unit based on the division results of the catchment units. The simulation calculation module is used to dynamically simulate the water accumulation change process of each catchment unit based on the elevation-water accumulation volume index table and the rainfall time series data, and output the waterlogging simulation results.

[0024] Compared with the prior art, the present invention has the following advantages: 1. By dividing the terrain into water catchment units with clear physical meaning and using a simplified linear water level-capacity relationship to describe their water accumulation behavior, the computational complexity is greatly reduced while preserving the physical laws of natural water catchment and drainage, achieving compatibility between high-precision simulation and second-level response.

[0025] 2. By pre-generating an elevation-water volume index table and an elevation-water depth index table for each catchment unit, the core calculations in the simulation process are converted into table lookup operations, which significantly improves the calculation speed. In actual tests, a single water accumulation calculation can be completed within 7-10 seconds, meeting the requirements of real-time early warning operationalization.

[0026] 3. By simulating the independent water accumulation, water level rise, and overflow merging of the catchment unit during the water accumulation increase stage, as well as the segmentation of connected areas and independent water receding during the water accumulation receding stage, the simulation results realistically reproduce the complete physical process of urban surface water accumulation from occurrence to receding. The correlation between the simulation results and the measured water accumulation distribution is over 80%. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the urban flooding simulation method based on topographic water catchment units in this invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] Please see the appendix Figure 1This invention provides a method and system for simulating urban flooding based on topographic catchment units, the implementation of which is as follows:

[0030] 1. Division of catchment units First, acquire digital elevation model data for the target area; This model adopts a dual division principle of "natural hydrological units + engineering drainage system". It automatically divides the terrain closed units, i.e. water catchment units, through watershed analysis algorithms to ensure that the surface runoff collection logic under natural conditions constructs a calculation zoning system that conforms to the physical mechanism of urban waterlogging.

[0031] Each catchment unit is an independent water-accumulating basin corresponding to a topographic depression. Each catchment unit has at least the elevation of the lowest point within the unit and the elevation of the lowest point on the boundary ridge as characteristic parameters.

[0032] 2. Generation of the Elevation-Water Accumulation Volume Index Table For each catchment unit, an elevation-water volume index table for that catchment unit is generated in advance; The elevation-water volume index table is a lookup table generated by integrating and summing water catchment units as the basic calculation units. It is used to record the water volume corresponding to different water levels.

[0033] Suppose a certain water catchment unit Z k The set of grid pixels covered is G k The planar size of each grid pixel is Δx * Δy (meters), the effective elevation value of each raster pixel is H eff ( i, j ).

[0034] The rules for determining the effective elevation value are as follows: For non-building raster pixels, the effective elevation value is the original digital elevation model (DEM) elevation value of that pixel; for raster pixels containing buildings, the effective elevation value is the sum of the ground surface elevation value and the flooding height of the building threshold.

[0035] The potential water level within the catchment unit h From the lowest elevation to the highest elevation within the unit, according to the set step size. Δh Discretization, for each discrete water level h Calculate all conditions within the catchment unit that satisfy the following conditions. H eff ( i , j )≤ h The sum of the water volumes corresponding to the grid pixels: V k (h )=∑( i, j )∈ G k max(0, h - H eff ( i, j ))* Δx * Δy The above V k ( h ) and water level h The corresponding relationship is stored as a lookup table, which yields the elevation-water volume index table for the catchment unit.

[0036] The volume value of a pixel is based on the catchment unit containing that pixel. That is, the volume value of a point represents the "volume value of the largest and deepest catchment unit corresponding to that point", which is the sum of the elevation integrals of all points below that point in the catchment unit.

[0037] 3. Generation of the Elevation-Water Depth Index Table This embodiment also pre-generates an elevation-water depth index table.

[0038] For each grid pixel ( i , j ), and pre-store its effective elevation values. H eff ( i , j This forms an elevation-water depth index table.

[0039] During the simulation, for a given water level... h water Arbitrary grid pixels ( i , j The depth of the accumulated water can be quickly obtained using the following formula: Depth ( i, j ) = max(0, h water -DEM_H [ i, j ]) 4. Water level-capacity relationship model Water level in each catchment unit h With water storage capacity V The following relationship exists between them: V ( h )= A 0* ( h - h min ), h min ≤ h≤ h ridge in, h min This is the elevation of the lowest point in the catchment area. h ridge This is the elevation of the lowest point on the ridge line of the catchment unit's boundary. A 0 represents the baseline area parameter for this catchment unit.

[0040] The mathematical model for the topographic capacity curve is as follows: For a given "bowl" shaped terrain (i.e., drainage block), its water level-capacity relationship can be approximately expressed as the above formula.

[0041] 5. Dynamic water accumulation evolution simulation For each calculation period Δt The change in water volume within the catchment unit is calculated using the water balance equation: ΔV =( P * A * C - Q out －I )* Δt in, ΔV This represents the change in water volume over a given period of time. P The intensity of rainfall during the period. A The area of ​​the catchment unit. C The comprehensive runoff coefficient, Q out For the outflow of the drainage system, I This represents the amount of infiltration loss.

[0042] Stage of increasing water accumulation: The water accumulation process within a drainage block begins by evenly submerging each "bowl". When the water level in a small "bowl" reaches the ridge line, the water overflows into other lower, unfilled "bowls". When the water level in a lower "bowl" rises to the ridge line of another "bowl", the two "bowls" merge into a larger "bowl" and continue to expand upwards.

[0043] When the water level of a catchment unit reaches the lowest point elevation on its boundary ridge, the excess water overflows into the adjacent catchment unit.

[0044] The floodwaters recede during the receding phase: The drainage process starts from each "bowl" in the whole system. Low-lying areas with relatively small water storage capacity are the first to be drained, while low-lying areas with large water storage capacity take longer to drain. The drainage process is a different hydrological logic from the water accumulation process.

[0045] When the water level in a catchment unit drops below its internal topographic ridge, the originally connected waterlogged area is divided into multiple independent catchment units.

[0046] The recession process of a single catchment unit is simulated using an exponential decay model: h ( t )= h 0* e －αt + h residual in, h ( t )for t The depth of the water at any given time h 0 represents the initial water depth. a This is the coefficient for the rate of water discharge. h residual This represents the residual water depth.

[0047] The drainage process is driven by three mechanisms: surface drainage, infiltration, and evaporation.

[0048] Furthermore, the target area can be pre-divided into multiple drainage blocks, each containing at least one catchment unit. A drainage block refers to the smallest hydrological calculation and management unit in the urban drainage system that is served by a complete, hierarchical network of pipes and facilities and has clear boundaries. Each drainage block is independent, and water will not flow between blocks. The growth and drainage of water are completed independently within the drainage block.

[0049] Furthermore, the rainfall time series data may include historical rainfall data, short-term forecast rainfall data, and numerical model forecast rainfall data. By splicing historical rainfall data with forecast rainfall data, a continuous rainfall input sequence is formed, and the model is driven by historical rainfall data to obtain the initial water accumulation state.

[0050] This embodiment also provides an urban flooding simulation system based on topographic catchment units to implement the above method, including: The data acquisition module is used to acquire digital elevation model data and rainfall time series data for the target area; The preprocessing module is used to divide the terrain within the target area into at least one closed catchment unit based on the digital elevation model data, and to pre-generate an elevation-water volume index table for each catchment unit based on the division results of the catchment units. The simulation calculation module is used to dynamically simulate the water accumulation change process of each catchment unit based on the elevation-water accumulation volume index table and the rainfall time series data, and output the waterlogging simulation results.

[0051] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A method for simulating urban flooding based on topographic catchment units, characterized in that, Includes the following steps: Obtain digital elevation model data for the target area; Based on the digital elevation model data, the terrain within the target area is divided into at least one closed catchment unit. For each of the aforementioned water catchment units, an elevation-water accumulation volume index table for that water catchment unit is generated in advance; Acquire rainfall time series data, and dynamically simulate the water accumulation change process of each catchment unit based on the elevation-water accumulation volume index table, and output the waterlogging simulation results.

2. The urban flooding simulation method based on topographic catchment units according to claim 1, characterized in that, The target area is pre-divided into multiple drainage blocks, and each drainage block contains at least one water collection unit.

3. The urban flooding simulation method based on topographic catchment units according to claim 1, characterized in that, The catchment unit is an independent water-collecting basin corresponding to a topographic depression. Each catchment unit has at least the lowest point elevation within the unit and the lowest point elevation on its boundary ridge as characteristic parameters.

4. The urban flooding simulation method based on topographic catchment units according to claim 3, characterized in that, Water level of each of the aforementioned water collection units h With water storage capacity V The following relationship exists between them: V ( h )= A 0* ( h-h min )， h min ≤ h ≤ h ridge in, h min This is the elevation of the lowest point in the catchment area. h ridge This is the elevation of the lowest point on the boundary ridge line of the catchment unit. A 0 represents the baseline area parameter for this catchment unit.

5. The urban flooding simulation method based on topographic catchment units according to claim 1, characterized in that, The elevation-water volume index table is a lookup table generated by integrating and summing the water catchment units as the basic calculation units, and is used to record the water volume corresponding to different water levels.

6. The urban flooding simulation method based on topographic catchment units according to claim 1, characterized in that, Also includes: An elevation-water depth index table is pre-generated, which stores the effective elevation value of each raster pixel; The effective elevation value is the ground elevation value of the grid pixel. For the grid pixel where the building is located, its effective elevation value is the sum of the ground elevation value and the flooding height of the building threshold. During the simulation, the water depth of any grid pixel is obtained by looking up the table based on the given water level and the elevation-water depth index table.

7. The urban flooding simulation method based on topographic catchment units according to claim 1, characterized in that, The water accumulation process includes a water accumulation increase phase and a water accumulation recede phase; During the water accumulation phase, when the water level of a catchment unit reaches the lowest point elevation on its boundary ridge, the excess water overflows into adjacent catchment units. During the receding phase of floodwaters, when the water level within a catchment unit drops below its internal topographic ridgeline, the previously connected flooded area is divided into multiple independent catchment units.

8. The urban flooding simulation method based on topographic catchment units according to claim 7, characterized in that, During the water receding phase, the water receding process of a single catchment unit is simulated using the following model: h ( t )= h 0* e －αt + h residual in, h ( t )for t The depth of the water at any given time h 0 represents the initial water depth. a The coefficient for water discharge rate. h residual This represents the residual water depth.

9. A system for implementing the urban flooding simulation method based on topographic catchment units as described in any one of claims 1-8, characterized in that, include: The data acquisition module is used to acquire digital elevation model data and rainfall time series data for the target area; The preprocessing module is used to divide the terrain within the target area into at least one closed catchment unit based on the digital elevation model data, and to pre-generate an elevation-water volume index table for each catchment unit based on the division results of the catchment units. The simulation calculation module is used to dynamically simulate the water accumulation change process of each catchment unit based on the elevation-water accumulation volume index table and the rainfall time series data, and output the waterlogging simulation results.

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