Analysis of Flood Control Effectiveness in Kali Sadar Regency and City of Mojokerto

Abstract

Kali Sadar is part of the main drainage system in some areas of Mojokerto Regency and City. The main channel of Kali Sadar has a length of ± 23,211 Km with a drainage area of ± 614,92 Km². And has an upstream elevation of + 900 meters and an elevation of + 20 meters downstream from sea level. Flood control planning is carried out through river normalization analysis, slope reinforcement work planning, and embankment planning. All schemes are carried out so that the planned flood discharge is able to reach the ideal condition of the flood water level in the river. The study also reviewed through the planning of drainage facilities in the form of pump houses and retention ponds. In the results of the HEC-RAS analysis the results of the planned discharge used were a 25-year return period with a maximum discharge of 1080 m2/s. After simulating there is a cross section experiencing overtopping, to overcome overtopping, parape embankments are installed and with slope reinforcement work (revetment) on the slopes of the right and left sides of the river. The purpose of slope reinforcement is to accelerate the direction of river flow towards downstream so that there is no sediment erosion, by changing the manning value. However, after the flood control circuit, the cross section of the stream is only able to accommodate a maximum discharge capacity of 151.98 m2/s. For that, it is necessary to plan a pump house. Drainage facilities, in tackling the problem of excess runoff, pump houses are used in 5 locations with a plan of 80,000 m2 and a depth of 4.5 m. The plan uses 3 pump units with a capacity of 4.32 m2/s through an operating system of 4 inflow gates and 4 outflow gates which have a door width of 4.125 m and a height of 3.5 meters. pumps turn on when the water level is 0.08 m, 2 pumps will turn on when the water level is 0.30 m, and 3 pumps will turn on when the water level is 0.39 m.