Page - 887 - in Book of Full Papers - Symposium Hydro Engineering

4.1. FLOOD CONDITIONS AFTER DAM BREAK The study of flood conditions based on dam break is aimed at applying the result of flood conditions and the flood flow period to the preparation of action plans in case of emergency to cope with situations arising in the event of dam failure. Three dam failure events are identified: flood loading, static loading and earthquake loading. [1] Flood loading is analyzed to obtain the maximum flood boundary. The study of six case studies found that the most severe flood case that is caused by the failure of mae suai dam in case of the pmf to mae suai reservoir and the 10,000-year return flood in downstream or mae lao river basin areas. Flood conditions of case study are shown in figure 6. The flooded area is about 181 km2. [2] Static Loading is analyzed to determine the flood boundary in case of dam failure by considering that water levels and downstream or Mae Lao River Basin areas are normal and no overflow occurs. The study result revealed that flooded areas are less than the first event. where the reservoir water is at normal high water level. Flood conditions are shown in Figure 7. Flooded areas are about 102 km2. [3] Earthquake Loading is analyzed as a scenario to consider impacts of dam failure in the event of earthquakes and in case of the 10,000-year return flood in downstream or Mae Lao River Basin areas. The study result shows that flooded areas are the same as case 1 4.2. AREAS AFFECTED BY DAM BREAK The boundary of areas affected by floods due to failure of Mae Suai Dam will change in accordance with characteristics and severity of dam failure in different scenarios. As a result of hydraulics analysis using mathematical models in preparation for flood maps, Mae Suai dam failure is analyzed in various scenarios to study flood conditions, the boundary of affected areas and severity so that damages can be assessed by using flood map data overlapping with area condition data. The analysis of different case studies indicated that the failure of Mae Suai Dam in case of flood conditions results in the most flooded areas as shown in Figure 8. Affected areas include both banks of the Mae Suai River from the area below Mae Suai Dam to the confluence of the Mae Lao River and both banks of the Mae Lao River from Ban Thung Yao, Si Thoi Sub-district, Mae Suai District to the confluence of the Kok River. The boundary of flooded areas in each area depends on topography and drainage potential of the Mae Suai and Mae Lao Rivers in that period. Flooded areas cover some areas in five districts of Chiang Rai Province – Mae Suai, Mae Lao, Phan, Mueang Chiang Rai and Wiang Chai districts and four municipalities: Wiang Suai, Mae Suai, Mae Lao and Pa Ko Dam sub-district municipalities. 887