Multi-strategy collaborative waterlogging treatment method suitable for multi-scene rainfall and used in urban and rural polder area with limited drainage

Abstract

The invention discloses a drainage limited urban and rural polder area multi-strategy collaborative waterlogging treatment method adapting to multi-scene rainfall. The method comprises the following steps of current situation investigation and multi-angle waterlogging drainage influence factor analysis; the polder area flood drainage is divided and partitioned; setting different levels of rainfall scenes; checking the drainage capacity of different scenes; the invention discloses a multi-strategy fusion collaborative waterlogging treatment method. According to the method, a multi-strategy-fused collaborative waterlogging treatment method of controlling irrigation and recession, enhancing regulation and storage capacity, enhancing gate station scheduling, opening up an emergency discharge bearing area and implementing plan management and responsibility and suitable for multi-scene rainfall is adopted, the corresponding waterlogging treatment plan can be selected according to the forecast rainfall level and by combining the typical section control water level of the inland river, and the water level can be controlled in a real-time manner. The method overcomes the defects that a traditional method is not high in adaptability, insufficient in emergency capacity, weak in collaboration and the like, life and property safety of people in the region is effectively guaranteed, regional waterlogging loss is reduced to the minimum, meanwhile, sustainable development of the regional economy and society is guaranteed, and remarkable economic benefits and social benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of flood control and waterlogging removal in embankment areas, and in particular to a multi-strategy coordinated waterlogging control method for urban and rural embankment areas with limited drainage that is adaptable to multiple precipitation scenarios. Background Art

[0002] The reasons for the limited drainage channels or water volume in the polder area are: first, the external drainage pump station group in the polder area may be forced to shut down when the water level of the external river exceeds the warning line, resulting in aggravated waterlogging; second, the traditional detention area may be insufficient in volume or occupied by a large amount of construction land; third, the underground space in urban areas and the water storage capacity of large fields in agricultural areas may not be fully utilized to reduce or stagger the peak flow; fourth, due to the influence of temporary cofferdams during the construction of water conservancy projects, the external drainage river channel may be cut off, affecting the flood discharge during the flood season, etc. The above reasons may cause the external drainage channels or water volume of the polder area to be affected or restricted to varying degrees, increasing the difficulty and degree of loss in regional waterlogging control during the flood season. The existing methods for flood control in urban and rural embankments have the following defects: the traditional drainage standards are single and fail to consider multi-level rainfall scenarios, which weakens the pertinence and adaptability of flood control methods in urban and rural embankments; the impact and constraints of limited external drainage channels or external drainage volume in urban and rural embankments are ignored, resulting in insufficient emergency response capabilities when encountering excessive or extreme rainstorms; there is a lack of analysis of the characteristics of urban and rural embankments and the integration of flood control measures from the aspects of irrigation, water withdrawal, field water storage capacity, temporary storage space outside the embankment, and emergency plan management, which greatly reduces the coordination and effectiveness of flood control methods.

[0003] Therefore, the flood control method for mixed urban and rural embankment areas under limited external drainage and different rainfall scenarios has important application value and guiding significance for ensuring the safety of life and property and sustainable economic and social development in the region. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage that is adaptable to multiple precipitation scenarios.

[0005] Technical solution: The method described in the present invention comprises the following steps:

[0006] (1) Current situation investigation and multi-angle analysis of factors affecting drainage;

[0007] (2) Drainage areas in the polder area are divided into sections and zones;

[0008] (3) Setting different levels of precipitation scenarios;

[0009] (4) Verification of drainage capacity under different scenarios;

[0010] (5) Multi-strategy integrated and coordinated flood control method.

[0011] Furthermore, the influencing factors of step (1) include underlying surface conditions, water system characteristics within the dike, hydraulic structures, land use properties, farmland types, drainage constraints, and water system characteristics outside the dike.

[0012] Furthermore, the step (2) includes determining the drainage sections and zones according to the topography of the polder area, the characteristics of the water system, the project layout and drainage experience, including high-water self-draining sections and low-water pumping sections, wherein the pumping areas are further divided into urban areas, agricultural areas and mixed areas.

[0013] Furthermore, step (3) includes setting different levels of precipitation scenarios according to the daily precipitation in the area, taking into account daily drainage, design standard drainage, and drainage in excess of the standard or extreme rainstorm conditions, including different rainfall levels of no rain, light rain, moderate rain, heavy rain, rainstorm, torrential rain, and extremely heavy rain.

[0014] Furthermore, the step (4) includes calculating the drainage modulus of urban areas, agricultural areas and mixed areas within the embankment respectively according to different levels of precipitation scenarios, using the average exclusion method, the time-period water balance method and the river network hydraulic model method, and then determining the corresponding drainage flow in combination with the catchment area of the sub-district or river; checking the flow capacity of the typical sections of the main river channels within the embankment area and the scale of the drainage pump stations in each sub-district, and calculating the allowable external drainage volume under the drainage restriction condition.

[0015] Furthermore, the multiple strategies in step (5) include strengthening flooding and water withdrawal control strategy, enhancing the storage capacity of the embankment area, strengthening the joint dispatching strategy of sluice stations, opening up emergency discharge areas, and implementing flood season management and responsibility strategies.

[0016] Furthermore, the enhanced irrigation and drainage control strategy includes:

[0017] In view of the limited drainage channels in the embankment area, irrigation and water discharge control measures in agricultural areas are strengthened to reduce the return water of irrigation in agricultural areas, including controlled irrigation of rice, time-sharing control of irrigation channel heads, and time-sharing control of channel water discharge gates.

[0018] Furthermore, the enhanced gate station joint dispatching strategy includes:

[0019] For different levels of precipitation scenarios, a river network hydrodynamic model is used to simulate different gates and stations, including a joint scheduling scheme for fixed pumping stations and mobile pumping stations. Based on a comprehensive evaluation of the simulation effects, a joint scheduling method for gates and stations corresponding to different precipitation scenarios is proposed, including time-sharing control of gate operation, graded control of drainage stations, emergency deployment of mobile pumping stations, and water level control of key sections of the river.

[0020] Furthermore, the strategy for opening up an emergency discharge area includes:

[0021] In the event of excessive or extreme rainstorms, the amount of water that cannot be discharged normally is determined based on the estimation of waterlogging volume and drainage volume in the dike area; then extraordinary measures are taken to open up a temporary emergency discharge area outside the dike.

[0022] Furthermore, the implementation of flood season management and responsibility strategies includes hierarchical and segmented management, monitoring, inspection and early warning, emergency response in key areas, and tightening of responsibilities, building a three-level responsibility system.

[0023] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: the present invention adopts a collaborative flood control method that integrates multiple strategies of "controlling flooding and water withdrawal + enhancing storage capacity + strengthening sluice station scheduling + opening up emergency discharge areas + implementing plan management and responsibilities" to adapt to multiple rainfall scenarios. It can control the water level according to the predicted rainfall level and the typical section of the inland river, and select the corresponding flood control plan, which makes up for the defects of traditional methods such as poor adaptability, insufficient emergency capacity, and weak coordination. It is conducive to protecting the lives and property of people in the region, minimizing the losses caused by regional flooding, and at the same time ensuring the sustainable development of regional economy and society, with significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flow chart of the steps of the present invention;

[0025] Figure 2 This is the relationship decision matrix diagram corresponding to multi-strategy coordinated flood control under different precipitation scenarios. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0027] The example selected here is a typical mixed urban and rural area, where the urban area is 118 km 2 , agricultural area 159km 2 . The overall terrain of the region is high in the northwest and low in the southeast, and the main drainage direction is from northwest to southeast. Due to the influence of the construction of water conservancy projects outside the polder area, some flood channels outside the polder area have been cut off, resulting in a certain degree of restriction on the drainage routes and water volume of the polder area. Therefore, based on the analysis of the current water system characteristics and drainage capacity of the polder area, the present invention proposes a multi-strategy coordinated flood control method for urban and rural polder areas with limited drainage that is adaptable to multiple precipitation scenarios. This method minimizes the degree of waterlogging losses in the target area under different precipitation scenarios while ensuring the normal irrigation water demand in the agricultural area. Figure 1 As shown, the specific implementation steps of the embodiment are as follows:

[0028] S1: Analysis of factors affecting drainage from multiple angles

[0029] Based on the current status survey and data collection of the target area of the embodiment, a comprehensive analysis is conducted on the internal and external factors that may affect regional waterlogging control, such as the underlying surface conditions, water system characteristics within the dike, supporting buildings, land use nature, farmland type, drainage constraints and water system characteristics outside the dike, to lay the foundation or provide a basis for the division of drainage areas and the selection of multi-scenario waterlogging control measures.

[0030] S2: Division of drainage control areas in multiple areas

[0031] According to the topography, water system characteristics, engineering layout and drainage experience of the polder area, combined with the "four separations and two controls" management requirements of the polder area, the polder area is divided into a high-water self-draining area (15 km northwest highland) and a 2 ) and 3 low-water pumping sections (north, southwest and southeast three pumping sections, a total of 262km 2 ), of which the north pumping area is the urban area, the southwest pumping area is the agricultural area, and the southeast pumping area includes both urban and agricultural areas.

[0032] S3: Multiple scenarios with different precipitation levels

[0033] According to the maximum daily precipitation data of the embodiment area over the years, the design daily precipitation for 5-year, 10-year and 20-year return periods was determined to be 151mm, 183mm and 213mm respectively through the hydrological statistical method. Based on this, the following 10 precipitation scenarios were set, replacing the traditional single design standard and improving the adaptability of the multi-strategy integrated flood control measures in the target area.

[0034] No rain (daily precipitation 0mm)

[0035] Light rain (daily precipitation 0-10mm)

[0036] Moderate rain (daily precipitation 10-25mm)

[0037] Heavy rain (daily precipitation 25-50 mm)

[0038] Heavy rain (daily precipitation 50-100 mm)

[0039] Heavy rain (≤ once every 5 years, daily precipitation 100-151mm)

[0040] Heavy rain (once in 5-10 years, daily precipitation 151-183 mm)

[0041] Heavy rain (once in 10 to 20 years, daily precipitation 183-213 mm)

[0042] Heavy rain (> once every 20 years, daily precipitation 213-250mm)

[0043] Extremely heavy rain (daily precipitation > 250 mm)

[0044] S4: Multi-directional drainage flow calculation and verification

[0045] According to different levels of precipitation scenarios, the average exclusion method and the water balance method by time period are used to calculate the drainage modulus of urban areas, agricultural areas, and mixed areas within the dike, and then the corresponding drainage flow is determined based on the catchment area of the zone. After calculation, the design drainage flow of the 5-year and 10-year flood seasons in the example area is 254m 3 / s and 398m 3 / s, while the total design flow of the existing drainage pump station is 296.5m 3 / s, it can be seen that the overall area of the embodiment has reached the 5-year return standard, and there is still a gap of 101.5m with the 10-year return standard. 3 / s.

[0046] S5: Multi-strategy integrated collaborative flood control method

[0047] Based on the verification of drainage capacity of each area in the implementation example, a collaborative flood control method integrating multiple strategies is proposed, corresponding to different levels of precipitation scenarios, including "controlling water withdrawal in irrigation areas, enhancing storage capacity within dikes, strengthening joint scheduling of sluice stations, opening up emergency discharge areas, and implementing flood season management and responsibilities."

[0048] S51: No rain

[0049] Controlled irrigation is implemented for rice: during the rice flooding period, the irrigation rate is 100m 3 / mu, 5 days to complete the field irrigation, the irrigation quota during the growth period is 25m 3 / mu, with a 6-7 day irrigation cycle, 3 days of irrigation and 3-4 days of rest, for a total of 14 irrigations. The irrigation district management office determined the opening plan for each water outlet gate based on the irrigation system of the irrigation district canals.

[0050] Time-sharing control of the headwaters (discharge gate): management and control are carried out according to irrigation requirements and flood prevention requirements during the irrigation season; control is carried out according to ecological flow requirements during the non-irrigation season; the irrigation system and channel rotation system determined by the rice control irrigation mode along the channels work normally.

[0051] Control of sluice gates and drainage stations: Regulating gates along the main river channels within the polder area will maintain normal water storage according to ecological water storage requirements. Drainage pump stations will be activated when the water level in the river section on the inlet side exceeds the minimum operating level; otherwise, they will remain stationary. See Table 1 for the controlled water levels in the river section on the inlet side of the pump stations.

[0052] River water level control: During the non-flood season, major rivers are generally maintained at normal water levels, which should not fall below the drought limit. During the flood season, major rivers should be maintained below the flood control level. Based on rainfall forecasts and warnings issued by meteorological authorities, measures such as early closure of water intake gates and pre-lowering of river water levels should be implemented. See Table 2 for the control water levels at typical sections of major rivers.

[0053] Table 1 Controlled water level of the river section at the inlet side of the pump station

[0054]

[0055] Table 2 Controlled water levels of typical sections of major rivers

[0056]

[0057] S52: Light rain (daily rainfall <10mm)

[0058] Controlled irrigation of rice: same as above.

[0059] Time-sharing control of the headwaters (discharge gate): management and control are carried out according to irrigation requirements and flood prevention requirements during the irrigation season; control is carried out according to ecological flow requirements during the non-irrigation season; the irrigation system and channel rotation system determined by the rice control irrigation mode along the channels work normally.

[0060] Control of regulating gates and drainage stations: regulating gates are installed along the main rivers within the embankment area to store water normally according to the requirements of ecological water storage; the drainage pump station will be started when the water level in the river section on the inlet side exceeds the minimum operating water level, otherwise it will not be started.

[0061] River water level control: same as above.

[0062] S53: Moderate rain (10-25 mm per day)

[0063] Controlled irrigation of rice: same as above.

[0064] Time-sharing control of the head of the canal (discharge gate): the irrigation discharge gate is closed 6 hours in advance; the canal is managed normally, taking into account the utilization of rainwater resources while ensuring the safety of drainage and waterlogging reduction.

[0065] Control of regulating gates and drainage stations: regulating gates are set up along the main rivers within the embankment area to control the water level in front of the gates according to the scheduling plan; when the water level in the river section on the inlet side of the drainage pump station exceeds the minimum operating water level, the pump station will be started. If moderate rain or above is forecast, the water level must be lowered to the minimum operating level in advance. The number of units started will be adjusted in real time according to changes in water level and rainfall conditions.

[0066] River water level control: same as above.

[0067] S54: Heavy rain (daily rainfall 25-50 mm)

[0068] Controlled irrigation of rice: same as above.

[0069] Time-sharing control of the head of the canal (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 12 hours in advance; when the river water level reaches the warning level during the flood season, the water discharge gate at the tail of the channel will be closed if the weather forecast still shows heavy rain or above.

[0070] Control of regulating gates and drainage stations: regulating gates are set up along the main rivers within the embankment area to control the water level in front of the gates according to the scheduling plan; when the water level in the river section on the inlet side of the drainage pump station exceeds the minimum operating water level, the pump station will be started. If heavy rain or above is forecast, the water level must be lowered to the minimum operating level in advance. The number of units started will be adjusted in real time according to changes in water level and rainfall conditions.

[0071] Enhance the water storage capacity of the polder areas: Fully utilize the water storage capacity of ecological ditches and ponds within the polder areas, sunken green spaces in urban areas, and large fields in agricultural areas (except during direct seeding and transplanting, and the flooding depth and duration during different growth stages meet regulatory requirements) to intercept and store rainwater and drain it after the rain, achieving peak load reduction and staggered regulation. The recommended maximum water storage depth for rice fields in agricultural areas is 80mm during the greening and milky stages, and 120-140mm during other periods to avoid rush drainage, and discharge the water 2-3 days after rain.

[0072] River water level control: same as above.

[0073] S55: Heavy rain (daily rainfall 50-100 mm)

[0074] Controlled irrigation of rice: same as above.

[0075] Time-sharing control of the head of the canal (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 1 day in advance; when the river water level reaches the warning level during the flood season, if the weather forecast still shows heavy rain or above, the water discharge gate at the tail of the channel will be closed.

[0076] Control of regulating gates and drainage stations: regulating gates are set up along the main rivers within the embankment area to control the water level in front of the gates according to the scheduling plan; when the water level in the river section on the inlet side of the drainage pump station exceeds the minimum operating water level, the pump station will be started. If heavy rain or above is forecast, the water level must be lowered to the minimum operating level in advance. The number of units started will be adjusted in real time according to changes in water level and rainfall conditions.

[0077] Enhance the water storage function of the dike area: make full use of the water storage capacity of the ecological ditches and ponds wetlands, sunken green spaces in urban areas and large fields in agricultural areas within the dike area to intercept and store rainwater, drain water after rain, and achieve peak shaving and staggered regulation.

[0078] River water level control: same as above.

[0079] S56: Heavy rain (100-151 mm, ≤ once every 5 years)

[0080] Controlled irrigation of rice: same as above.

[0081] Time-sharing control of the canal head (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 1 day in advance; when the river water level reaches the warning level during the flood season, if the weather forecast still shows heavy rain or above, the water discharge gate at the tail of the channel will be closed.

[0082] Regulating gate control: Based on the river water level and weather forecast of heavy rain or above, Gate A is closed and drainage is carried out in sections; all other gates along the drainage river are opened and joint scheduling is implemented.

[0083] Drainage station control: Drainage pump stations are activated when the water level in the river section on the inlet side exceeds the minimum operating level. If heavy rain or above is forecast, the water level must be lowered to the minimum operating level. The number of pumps in operation is adjusted in real time based on water level and rainfall. During heavy rain with a return rate of less than 1 in 5 years, flood water will be primarily drained through Rivers 1, 2, 3, 4, and 5 within the dike to the southeast low-lying area. Drainage stations B6, B7, B8, and B9 will be activated in sequence, depending on the rainfall intensity. When a torrential rainstorm occurs once every five years, gate A is closed, and the north pumping and drainage area discharges the flood water into the outer-weihe River I through drainage stations B1, B2, B3, and B4; the southwest pumping and drainage area dispatches the flood water through gate B, and some of the flood water is discharged into the outer-weihe River II through drainage station B5, and some of the flood water is collected into River 5 through inner river 6 and then to the southeast pumping and drainage area; in the southeast area, gates C, D, and D are opened, and the flood water is mainly collected into the southeast pumping and drainage area through inner-weihe River 2, River 3, River 4, and River 5, and then discharged into the outer-weihe River III through drainage stations B6, B7, B8, and B9.

[0084] Put into operation mobile (temporary) pumping stations: According to the changes in river water level and rainfall conditions, mobile (temporary) pumping stations will be added along Outer River II and III to assist in pumping and drainage.

[0085] Enhance the water storage function of the dike area: make full use of the water storage capacity of the ecological ditches and ponds wetlands, sunken green spaces in urban areas and large fields in agricultural areas within the dike area to intercept and store rainwater, drain water after rain, and achieve peak shaving and staggered regulation.

[0086] River water level control: same as above.

[0087] S57: Heavy rain (151-183 mm, once in 5-10 years) - implemented according to the 10-year plan

[0088] Example scope 10-year design drainage flow 398m 3 / s, equipped with a drainage station with a design flow of 296.5m 3 / s, the overall gap is 101.5m 3 / s, and the drainage capacity is less than the design standard of once in 10 years.

[0089] Controlled irrigation of rice: same as above.

[0090] Time-sharing control of the canal head (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 1 day in advance; when the river water level reaches the warning level during the flood season, if the weather forecast still shows heavy rain or above, the water discharge gate at the tail of the channel will be closed.

[0091] Regulating gate control: Based on the river water level and weather forecast of heavy rain or above, Gate A is closed and drainage is carried out in sections; all other gates along the drainage river are opened and joint scheduling is implemented.

[0092] Drainage station control: When encountering a 10-year heavy rainstorm, an emergency plan for super-standard drainage will be implemented, and all drainage pump stations will be started to drain water at full capacity.

[0093] Enhance the water storage function of the dike area: make full use of the water storage capacity of the ecological ditches and ponds wetlands, sunken green spaces in urban areas and large fields in agricultural areas within the dike area to intercept and store rainwater, drain water after rain, and achieve peak shaving and staggered regulation.

[0094] Put into use mobile (temporary) pumping stations: Based on changes in river water levels and rainfall conditions, mobile (temporary) pumping stations will be added along the outer rivers I, II, and III as appropriate to ensure emergency drainage; places where local waterlogging may occur within the dike will also be discharged into the inner river through mobile pumping stations.

[0095] Open up emergency storage areas outside the dikes: When a 10-year heavy rainstorm occurs, the riverbed and beach of the diked Outer River IV outside the dikes are used for temporary water storage. According to calculations, a 10-year heavy rainstorm will produce 27.87 million m3 of runoff. 3 The amount of water pumped to outer rivers I, II, and III is 21.35 million m 3 There is still 6.52 million m3 of accumulated water 3 The water cannot be discharged. If the outer river IV channel is activated to store water, with the cofferdam elevation of 8.5m (considering the super-height of 0.5m, the water level elevation is 8.0m), 15.1 million cubic meters of flood water can be stored. 3 , meeting the trough storage requirements for a 10-year rainstorm.

[0096] Emergency Plan Management and Responsibility Implementation: In the event of excessive or extreme rainstorms, it is particularly important to strengthen the management and responsibility implementation of flood season emergency plans. This implementation emphasizes "tiered and segmented management, monitoring, inspection, and early warning, emergency response in key areas, and tightening accountability." A comprehensive rainstorm monitoring system will be established to closely monitor rainfall and water level fluctuations. 24-hour on-call inspections will be organized to track rainfall, water conditions, construction conditions, and disaster situations. A dedicated emergency rescue team will be established to provide timely assistance and ensure life safety. Traffic restrictions will be promptly issued to strengthen water source management, livelihood security, and disease prevention and control in flooded areas. A three-tiered responsibility system will be established, encompassing provinces, cities, and counties (districts), ensuring on-the-ground command.

[0097] River water level control: same as above.

[0098] S58: Heavy rain (183-213 mm, 10-20 year return) - implemented according to the 20-year return plan

[0099] Example scope: 20-year design drainage flow rate 572m 3 / s, equipped with drainage flow rate of 296.5m3 / s, the overall gap is 275.5m 3 / s, and the drainage capacity is seriously insufficient to meet the design standard of a 20-year flood.

[0100] Controlled irrigation of rice: same as above.

[0101] Time-sharing control of the canal head (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 1 day in advance; when the river water level reaches the warning level during the flood season, if the weather forecast still shows heavy rain or above, the water discharge gate at the tail of the channel will be closed.

[0102] Regulating gate control: Gate A is closed and segmented drainage is implemented; all other gates along the river are opened and joint scheduling is implemented.

[0103] Drainage station control: When encountering a 20-year heavy rainstorm, an emergency plan for super-standard drainage will be implemented, and all drainage pump stations will be started to drain water at full capacity.

[0104] Enhance the water storage function of the dike area: make full use of the water storage capacity of the ecological ditches and ponds wetlands, sunken green spaces in urban areas and large fields in agricultural areas within the dike area to intercept and store rainwater, drain water after rain, and achieve peak shaving and staggered regulation.

[0105] Put into use mobile (temporary) pumping stations: Based on changes in river water levels and rainfall conditions, mobile (temporary) pumping stations will be added along the outer rivers I, II, and III as appropriate to ensure emergency drainage; places where local waterlogging may occur within the dike will also be discharged into the inner river through mobile pumping stations.

[0106] Open up emergency storage areas outside the dikes: When a 10-year heavy rainstorm occurs, the riverbed and beach of the diked Outer River IV outside the dikes are used for temporary water storage. According to calculations, a 20-year heavy rainstorm will produce 36.5 million m3 of runoff. 3 The amount of water pumped to outer rivers I, II, and III is 23.48 million m 3 There is still 13.02 million m3 of accumulated water 3 The water in the outer river IV channel is activated, and with the cofferdam elevation of 8.5m, 15.1 million cubic meters of flood water can be stored. 3 , meeting the trough storage requirements of a 20-year rainstorm.

[0107] Emergency plan management and responsibility implementation: same as above.

[0108] River water level control: same as above.

[0109] S59: Heavy rain (213-250 mm, > once every 20 years)

[0110] Controlled irrigation of rice: same as above.

[0111] Time-sharing control of the canal head (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 1 day in advance; when the river water level reaches the warning level during the flood season, if the weather forecast still shows heavy rain or above, the water discharge gate at the tail of the channel will be closed.

[0112] Regulating gate control: Gate A is closed and segmented drainage is implemented; all other gates along the river are opened and joint scheduling is implemented.

[0113] Drainage station control: Implement the super-standard drainage emergency plan, and all drainage pump stations will start up to drain water at full capacity.

[0114] Enhance the water storage function of the dike area: make full use of the water storage capacity of the ecological ditches and ponds wetlands, sunken green spaces in urban areas and large fields in agricultural areas within the dike area to intercept and store rainwater, drain water after rain, and achieve peak shaving and staggered regulation.

[0115] Deployment of mobile (temporary) pumping stations: Based on changes in river water levels and rainfall patterns, mobile (temporary) pumping stations will be added along Outer Rivers I, II, and III as needed to provide emergency drainage. Where localized waterlogging may occur within the dikes, mobile pumping stations will also be used to drain water into the inner rivers. The location, number (flow rate), and feasibility of mobile pumping stations must be fully considered when commissioning.

[0116] Open up emergency storage areas outside the dikes: Use the riverbed and beach of the dike IV outside the dikes for temporary water storage. According to calculations, a 20-year flood will produce 42.84 million m3 of runoff. 3 (Based on a daily rainfall of 250 mm), the amount of water pumped to outer rivers I, II, and III is 25.62 million m 3 There is still 17.22 million m3 of accumulated water 3 The water cannot be discharged. The water in the outer river IV channel is activated. With the existing cofferdam elevation of 8.5m, 15.1 million cubic meters of flood water can be stored. 3 , which cannot meet the storage requirements, it is recommended to raise the cofferdam to 9.0m (considering the super-height of 0.5m, the water storage level elevation is 8.5m), which can store 17.35 million m3 of flood water. 3 , basically meeting the storage requirements for heavy rainstorms (213-250mm) that occur once every 20 years.

[0117] Emergency plan management and responsibility implementation: same as above.

[0118] River water level control: same as above.

[0119] S510: Extremely heavy rain (daily rainfall > 250 mm)

[0120] Controlled irrigation of rice: same as above.

[0121] Time-sharing control of the canal head (discharge gate) and the water discharge gate: the irrigation water discharge gate will be closed 1 day in advance; when the river water level reaches the warning level during the flood season, if the weather forecast still shows heavy rain or above, the water discharge gate at the tail of the channel will be closed.

[0122] Regulating gate control: Gate A is closed and segmented drainage is implemented; all other gates along the river are opened and joint scheduling is implemented.

[0123] Drainage station control: Implement the super-standard drainage emergency plan, and all drainage pump stations will start up to drain water at full capacity.

[0124] Enhance the water storage function of the dike area: make full use of the water storage capacity of the ecological ditches and ponds wetlands, sunken green spaces in urban areas and large fields in agricultural areas within the dike area to intercept and store rainwater, drain water after rain, and achieve peak shaving and staggered regulation.

[0125] Deployment of mobile (temporary) pumping stations: Based on changes in river water levels and rainfall patterns, mobile (temporary) pumping stations will be added along Outer Rivers I, II, and III as needed to provide emergency drainage. Where localized waterlogging may occur within the dikes, mobile pumping stations will also be used to drain water into the inner rivers. The location, number (flow rate), and feasibility of mobile pumping stations must be fully considered when commissioning.

[0126] Open up emergency storage areas outside the dike: Use the riverbed and beach of the diked Outer River IV outside the dike for temporary water storage. With the existing cofferdam elevation of 8.5m, it can store 15.1 million cubic meters of flood water. 3 The cofferdam was raised to 9.0m, which can store 17.35 million cubic meters of flood water. 3 The cofferdam was raised to 9.0m, which can store 17.35 million cubic meters of flood water. 3 The cofferdam was raised to 9.5m, which can store 20.1 million cubic meters of flood water. 3 The cofferdam was raised to 10m, which can store 24.7 million cubic meters of flood water. 3 If there is a heavy rainstorm and the cofferdam has been raised by 1.5m, and the volume of water stored in the river channel is still insufficient, consider draining the water stored in the river channel to other nearby temporary detention areas (using temporary pumping stations for drainage).

[0127] Emergency plan management and responsibility implementation: same as above.

[0128] River water level control: same as above.

Claims

1. A multi-strategy coordinated flood control method for urban and rural areas with limited drainage adapted to multiple precipitation scenarios, characterized by: The steps include: (1) Current situation investigation and multi-angle analysis of factors affecting drainage; (2) Drainage areas in the polder area are divided into sections and zones; (3) Setting different levels of precipitation scenarios; (4) Verification of drainage capacity under different scenarios; (5) Multi-strategy integrated and coordinated flood control method.

2. The multi-strategy coordinated flood control method for urban and rural areas with limited drainage adapted to multiple precipitation scenarios according to claim 1 is characterized in that: The factors affecting step (1) include underlying surface conditions, water system characteristics within the dike, hydraulic structures, land use properties, farmland types, drainage constraints, and water system characteristics outside the dike.

3. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 1 is characterized in that: The step (2) includes determining drainage sections and zoning based on the topography of the polder area, water system characteristics, engineering layout and drainage experience, including high-water self-draining sections and low-water pumping sections, where the pumping and drainage areas are further divided into urban areas, agricultural areas and mixed areas.

4. The multi-strategy coordinated flood control method for urban and rural areas with limited drainage adapted to multiple precipitation scenarios according to claim 1 is characterized in that: The step (3) includes setting different levels of precipitation scenarios according to the daily precipitation in the region, taking into account daily drainage, design standard drainage, and drainage conditions exceeding the standard or extreme rainstorm, including different rainfall levels of no rain, light rain, moderate rain, heavy rain, rainstorm, heavy rainstorm, and extremely heavy rainstorm.

5. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 1 is characterized in that: The step (4) includes calculating the drainage modulus of urban areas, agricultural areas and mixed areas within the embankment respectively according to different levels of precipitation scenarios by using the average exclusion method, the time-period water balance method and the river network hydraulic model method, and then determining the corresponding drainage flow in combination with the catchment area of the sub-district or river; checking the flow capacity of the typical sections of the main river channels within the embankment area and the scale of the drainage pump stations in each sub-district, and calculating the allowable external drainage volume under the drainage restriction condition.

6. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 1 is characterized in that: The multiple strategies in step (5) include strengthening flooding and water withdrawal control strategy, enhancing the storage capacity of the embankment area, strengthening the joint dispatching strategy of sluice stations, opening up emergency discharge areas, and implementing flood season management and responsibility strategies.

7. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 6 is characterized in that: The enhanced irrigation and drainage control strategy includes: In view of the limited drainage channels in the embankment area, irrigation and water discharge control measures in agricultural areas are strengthened to reduce the return water of irrigation in agricultural areas, including controlled irrigation of rice, time-sharing control of irrigation channel heads, and time-sharing control of channel water discharge gates.

8. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 6 is characterized in that: The enhanced joint dispatching strategy for gate stations includes: For different levels of precipitation scenarios, a river network hydrodynamic model is used to simulate different gates and stations, including a joint scheduling scheme for fixed pumping stations and mobile pumping stations. Based on a comprehensive evaluation of the simulation effects, a joint scheduling method for gates and stations corresponding to different precipitation scenarios is proposed, including time-sharing control of gate operation, graded control of drainage stations, emergency deployment of mobile pumping stations, and water level control of key sections of the river.

9. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 6 is characterized in that: The strategies for developing emergency discharge areas include: In the event of excessive or extreme rainstorms, the amount of water that cannot be discharged normally is determined based on the estimation of waterlogging volume and drainage volume in the dike area; then extraordinary measures are taken to open up a temporary emergency discharge area outside the dike.

10. The multi-strategy coordinated flood control method for urban and rural embankment areas with limited drainage adapted to multiple precipitation scenarios according to claim 6, characterized in that: The implementation of flood season management and responsibility strategies includes hierarchical and segmented management, monitoring, inspection and early warning, emergency response in key areas, and tightening of responsibilities, building a three-level responsibility system.

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