STUDY ON FLOOD REDUCTION FROM URBAN DRAINAGE AND RIVERS THROUGH RETENTION POND IN LANGSA CITY – ACEH PROVINCE
Flooding Langsa City is caused by the weakening of a river and urban drainage in accommodating excess discharge due to extreme rain events. due to this flood every year several villages in Langsa City experience flood inundation. partly sourced from rivers and urban drainage. this is an important task in overcoming flooding in Langsa Cityto reduce peak flood discharge during the high rainy season in the future. The aim of this study was to find out the magnitude of the planned Q100 annual peak flood discharges in urban drainage and the Langsa river by simulating 1-D and 2-D runoff flows that are able to determine the distribution of land that has the potential to flood hazard risk. find out the location of the appropriate retention pond. to reduce flood peaks from urban and river drainage in order to be able to store water as raw water supply in urban areas. There are several methods used for analysis in this study. namely the method of maximum rainfall frequency. Nakayashu Synthetic Unit Hydrograph (SUH) and rational method used for peak river discharge and urban drainage analysis with the aid of integrity between HECRAS 5.01 and GIS. The results indicated that good locations for retention ponds were located in Pondok Keumuning Village, Meurandeh Dayah Village, lengkong village, Pondok Kelapa village, and Sungai Pauh village resulted in a 24.64% reduction in flooding on the Langsa river. but to increase the reduction of flood discharge. normalization of the river needs to beundertaken.
Water Level, Flood Risk, Retention Pond Location, And Flood Discharge.