Flood Analysis on Lake Tempe, South Sulawesi

Tempe Lake is one of the largest lakes in Wajo, Sopen, and Siddenreng Rappang in southern Sulawesi. Lake Tempe is the reservoir of his five major rivers: Bilokka, Lidaratangu, Masaka, Siddenreng, Bira and Walane. The lake offers many benefits to the community such as securing water resources, flood control, agriculture, fishing, and tourism. However, approximately 20–40 cm of silt is produced annually. This can cause flooding in the surrounding areas. Therefore, the restoration of Lake Tempe is necessary to mitigate flooding caused by continuous sedimentation. The Department of Public Works and Housing has developed a phased dredging plan to improve the capacity of Lake Tempe. Later, as no disposal sites were available, dredged materials were used to build several artificial islands along the perimeter of the lake. After the reconstruction project was completed, two major floods occurred, overtopping embankments. Therefore, the design analysis of embankments is required. Analysis indicates that two flood events occur, with a 20-year return period flood and a 50-year return period flood at elevations of 8.36 m and 9.2 m. From hydraulic analysis it is found that flood embankment height of 10 m is overtopped by water level of total 9.56 m and 10.4 m respectively because of wave run up. For a 20-year return period, there is an indication that slope stability and settlement problems affect flood events. It can be concluded that flood problems occur because of extreme events and the failure of flood embankments due to overtopping.