FLOOD OVERFLOW MODELING FOR ANALYSIS OF IMPACT LOSS AND FLOOD CONTROL SCENARIO SELECTION (Case Study: Karang Mumus River Samarinda City)

• Main Author: Khafid, Abdul
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/39978
• Institution: Institut Teknologi Bandung

Samarinda is one of the cities in Indonesia that develops in the area around the Mahakam River which has a high potential for flooding. Various studies and plans for the flood control infrastructure have been carried out and some have been carried out, but flooding still occurs every year. Flood hydrograph analysis was carried out using the SCS and Nakayasu methods. Hydraulic analysis and flood overflow modeling were carried out using HEC-RAS 5.0.5 1D/2D software. The analysis of losses due to floods is calculated based on criteria from BNPB. The flood discharge design of the Karang Mumus Hilir sub-watershed at the time of the return of 2 years, 5 years, 10 years, 20 years, 25 years, 50 years, and 100 years was 185.5 m3/s; 213 m3/s; 231.2 m3/s; 248.6 m3/s; 254.1 m3/s; 271,1 m3/s; and 288 m3/s. The inundation area of the existing simulation in Q25 years discharge reaches 903.9 ha. The scenario of dredging the Benanga Dam in the simulation of the Q25 years flood shows an inundation area of 856.6 ha; the construction of the Muang Dam shows an inundation of 885.4 ha; and normalization of the Karang Mumus Hilir River shows an inundation of 873 ha. The normalization of Karang Mumus Hilir River has the effect of reducing the number of houses most affected by floods, reaching 1680 units, compared to dredging the Benanga Dam as many as 340 units and the construction of the Muang Dam as many as 122 units. Economically, the normalization of the Karang Mumus Hilir River provides the greatest benefits, with an NPV of IDR 912.5 billion; BCR of 2.13; and IRR of 17.82%. Dredging of Benanga Dam gives an NPV of IDR 33.5 billion; BCR of 1.43; and IRR of 12.55%. While the construction of the Muang Dam is not profitable with an NPV of minus (IDR 8.1 billion); BCR of 0.97; and IRR of 7.20%. Qualitative level of risk analysis shows that the risk category in the flood mitigation scenario above for Q25 years flood discharge is included in the moderate risk category, except for river normalization scenarios which are included in the low risk category.