STUDY ON THE EFFECTIVENESS OF TONDANO AND TIKALA RIVER’S NORMALIZATION IN FLOOD RISK REDUCTION AT TIKALA RIVER’S FLOOD PLAIN MANADO CITY

• Main Author: Intan Sukmajati, Erha
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/50067
• Institution: Institut Teknologi Bandung

Manado is one of the major cities in Indonesia. Among six rivers that pass through the city of Manado, the area around the Tondano River and Tikala River is an area with a high level risk of flooding as occurred during the 2014 floods where there was a large flood giving considerable impact on the City of Manado. This study was carried out in the floodplain affected by the Tikala River which is a sub basin of Tondano River in the Manado City. Hydrological analysis using Nakayasu synthetic hydrograph unit of Q50 flood discharge downstream of the Tikala River was 420.503 m3/sec. Hydraulic analysis and 2D flood modeling using HEC-RAS 5.0.7 under existing conditions without flood control measures resulted an inundation area of 2.454 km2 with 43.90% on low hazard class (DV <0.75m2 / s), 9.62% on moderate hazard class (0.75 <DV <1.1 m2 / s), and 46.48% on high hazard class. Risk level analysis based on Perka BNPB No. 2 tahun 2012 in an existing condition resulted high risk level in Tikala Ares, Paal IV, Dendengan Luar, Dendengan Dalam, Ranomuut, Perkamil and Malendeng. Whereas in 2 villages, Tikala Baru and Banjer are in moderate risk level. The first scenario of flood control measures resulted an inundation area of 2.09 km2 or reducing inundation area by 14.59% and reduced flood risk in 4 sub-district i.e. Paal IV, Ranomuut, Perkamil dan Malendeng to moderate level. Second scenario of flood control measures resulted an inundation area of 0.95 km2, reducing the inundation area by 61.29% and reducing the risk level in Dendengan Luar from high risk level to low risk level. In Tikala Ares, Paal IV, Dendengan Dalam, Ranomuut, Perkamil and Malendeng from high risk level to moderate risk level, and also Banjer from moderate level to low level. Third scenario of flood control measures resulted an inundation area of 0.16 km2 or reducing the inundation area as wide as 93.09% and reducing the flood risk level of Paal IV, Dendengan Dalam and Malendeng to moderate risk level. The flood risk level of Tikala Ares, Dendengan Luar, Ranomuut and Perkamil reduced from high risk level to low risk level. And also reducing the flood risk level of Tikala baru and Banjer to low risk level. The first scenario reduced the flood losses potential of Rp272,420,621,446.00 and a BCR value of 1.04. The second scenario of flood control measures reduces the flood losses potential of Rp281,116,130,140.00 and a BCR value of 1.09. While the third scenario reduced potential flood losses of Rp306,042,271,191.00 and a BCR value of 1.03.