A New Flash Flood Warning Scheme Based on Hydrodynamic Modelling
2. Hydrodynamic Model
3. Materials and Methods
3.1. Hazard Index
3.2. Building Database of Critical Threshold Rainfalls
3.2.1. Modelling Scenarios
3.2.2. Calculation of Critical Rainfall
3.3. Flood Warning Operation Flow
- Determine the rainfall duration time according to the rainfall forecast.
- Determine the antecedent soil moisture type according to the 5-day accumulated rainfall (Table 2).
- Based on the rainfall duration and antecedent soil type determination, determine the corresponding critical rainfall from the database.
- Calculate the accumulated rainfall at the decision moment, . Calculate the accumulated rainfall at the warning moment, . The calculation time steps for both and are 15 min for a 1-h rainfall duration, while they are 30 min for both 3-h and 6-h rainfall durations.
- Compare the rainfall at the warning time, , and the critical rainfall, ; if > , send the warning information to the target community.
3.4. Comparison with Existing Systems and Limitations
4. Case Study
4.1. Introduction of Lengkou Catchment
4.2.1. Impact of Critical Hazard Index
4.2.2. Impact of Rainfall Duration
4.2.3. Impact of Antecedent Rainfall
4.3. Example of Flood Warning Operation
- According to the rainfall forecast (Table 3), the rainfall duration can be determined to be 3 h.
- As the flood season of the Lengkou catchment occurs in the growing season and the antecedent rainfall is 30 mm, the initial soil saturation is classified as dry (Table 2).
- Choose the critical rainfall for the catchment in relation to a 3-h rainfall duration and initial dry soil conditions from the critical rainfall database.
- Compute the accumulative rainfall at the warning moment, such as the last row of Table 3.
- Taking location Pa as an example, the critical rainfalls are 35 mm and 40 mm for PE and IE, respectively. At decision time = 1.0 h, the cumulative rainfall is 25 mm, and the rainfall forecasted for the next 30 min is 15 mm. Therefore, the cumulative rainfall at the warning time is 40 mm. If the rainfall intensity is assumed to be uniform during the next 30 min (i.e., from t = 1.0 to 1.5 h), the cumulative rainfall will reach 35 mm at t = 1.17 h (as shown in Figure 11). Thus, a PE warning will be sent to the people at Pa. The cumulative rainfall will reach 40 mm at = 1.5 h (as shown in Figure 12). Therefore, an IE warning should be sent to people at both locations Pa and Pb.
Conflicts of Interest
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|Rainfall Duration (h)||Total Rainfall (mm)||Modelling Duration (h)||Number of Scenarios||Notes|
|1||10, 20, 30, 40, 50, 60, 70, 80||3||8||Initial soil moistures are dry, medium, and saturated.|
|3||10, 25, 40, 55, 70, 85, 100||6||7|
|6||10, 30, 50, 70, 90, 110, 130, 150, 170||12||9|
|Antecedent Moisture Classes (AMC)||Total 5-day Antecedent Accumulated Rainfall (mm)||Ratio|
|Dormant Season||Growing Season|
|Cumulative rainfall at warning time:||10||25||40||45||65||63||60|
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Huang, W.; Cao, Z.; Huang, M.; Duan, W.; Ni, Y.; Yang, W. A New Flash Flood Warning Scheme Based on Hydrodynamic Modelling. Water 2019, 11, 1221. https://doi.org/10.3390/w11061221
Huang W, Cao Z, Huang M, Duan W, Ni Y, Yang W. A New Flash Flood Warning Scheme Based on Hydrodynamic Modelling. Water. 2019; 11(6):1221. https://doi.org/10.3390/w11061221Chicago/Turabian Style
Huang, Wei, Zhixian Cao, Minghai Huang, Wengang Duan, Yufang Ni, and Wenjun Yang. 2019. "A New Flash Flood Warning Scheme Based on Hydrodynamic Modelling" Water 11, no. 6: 1221. https://doi.org/10.3390/w11061221