Korea experiences increasing annual torrential rains owing to climate change and river flooding. The government is expanding a new drainage pump station to minimize flood damage, but the river level has not been adjusted because of torrential rains. Therefore, the river level must be adjusted to operate the drainage pump station, and it can be adjusted through the reservoir of the drainage pump station. In this study, we developed a method for operating drainage pump stations to control the river level and verify the effectiveness of the proposed method. A stormwater management model (SWMM) was used to simulate the Suyeong River and Oncheon River in Busan, Korea. The rainfall data from 2011 to 2021 were investigated. The data were sorted into ten big floods that occurred in Busan. The model was calibrated with actual rainfall data. The water level of the Suyeong River and the Oncheon River was the highest in most simulations. The simulation results showed an average decrease of 3018.2 m3 in Suyeong River flooding, and the Oncheon River needed to be supplemented due to structural problems. As a result of the recombination by simply supplementing the structural problems of the Oncheon River, the average flooding of 194.5 m3 was reduced. The proposed method is economical and efficient for reducing urban stream flooding in areas susceptible to severe damage caused by climate change.
The friction velocity is a quantity with the dimensions of velocity defined by the friction stress and density of a wall surface at near wall of flow condition. Also, the friction velocity is the hydraulic parameter describing shear force at the bottom flow. Moreover, it is a very important factor in designing open channel and essential to determine the mixing coefficient in the main flow direction. The estimation of the friction velocity are such as methods using channel slope, linear law of the mean velocity at viscous sub-layer and direct measurement of wall shear stress, etc. In the present study, we propose a friction velocity equation that has been optimized by combining the concept of entropy, which is used in stochastic method, and to verify the proposed equation, the experimental data measured by Song was used. The R squared for friction velocities between proposed equation and friction velocity formula analyzed 0.999 to 1.000 in a very good agreement with each equation.
As stream discharge changes rapidly during a typhoon or stormy weather, it is very difficult to measure and calculate the real-time flow rate to create an effective disaster response plan in a short span of time. Existing bed slopes and energy slopes in particular are tricky to measure as they experience abrupt changes in their flow profiles. However, when the water level changes as the flow rate changes, the measurement is relatively simple. Therefore, an acoustic Doppler current profiler (ADCP) was installed at approximately 400 m north of Gangchang Bridge on the Geumho River to compare the measured flow rate with the actual flow rate. The mean velocity and the discharge were reflected in the Manning's mean velocity equation, and the water surface slopes were compared with the measured discharge using the ADCP data. The accuracy verification with R-squared yielded a fairly good result (0.8 to 0.9). The results of this study could help deliver quick and effective disaster forecasts in the future.
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