Feasibility study of flooding mitigation by physical river modification by lining method on slopes and river bed: case study of Yom River, Sukhothai province
Abstract:
This study is to propose the feasibility study for flood mitigation in the Lower Yom River basin of Sukhothai Provinces Muang District. The hypothesis is to improve the Yom Rivers discharge while flowing through the district. The mathematical simulation model HES-RAS version 5.0.1 (USACE, 2016) was applied to analyze in this study. The length of rivers improvement was varied from 2 km. in case 1 to 20 km. in case 10. The Yom Rivers station Y.4 (Sukhothais Muang District) was applied to be the center point of the study. The condition of maximum discharge capacity and the highest level of the Yom Rivers station Y.4 in the 2011 were used to compare with the Yom Rivers maximum flow after improving by concrete lining of river bottom and side slopes. In the 2011, at the Yom Rivers station Y.4 (Sukhothais Muang District) had a maximum flow rate of 685.20 cubic meters/second and the highest water level of 50.74 m. (MSL.). The numbers were used for calibration purpose. The result of calibration was the Yom Rivers Mannings n = 0.025 - 0.050 and the Yom Rivers Mannings n at the Yom Rivers station Y.4 = 0.025. The analysis of the physical river modification was simulated by letting Mannings n = 0.013, which represented concrete linings improvement at the Yom Rivers station Y.4. Different scenarios were simulated as the lining length of the river reach of 2 km., 4 km., 6 km., 8 km., 10 km., 12 km., 14 km., 16 km., 18 km., and 20 km., respectively. The result of this simulating study can reduce the water level of the Yom River by 0.06 m., 0.37 m., 0.52 m., 0.67 m., 0.82 m., 1.04 m., 1.19 m., 1.33 m., 1.46 m., and 1.59 m., respectively. The efficiency in case 2 (reducing the water level = 0.37 m.) can be compared to a diversion channel of 50 cubic meters/second and in case 3 (reducing the water level = 0.52 m.) can be compared to a diversion channel of 100 cubic meters/second. The best case in this study which is appropriate to mitigate in the Lower Yom River basin of Sukhothai Provinces Muang District is the case 5 (reducing the water level = 0.82 m.)