THE EFFECT OF RETURN PERIOD AND SEDIMENTATION ON THE CAPACITY OF RIVER DISCHARGE CAPACITY IN SAMARINDA CITY, EAST KALIMANTAN

Abstract

Factors that affect flooding are due to the dense population that occupies the floodplain of the river, the city's drainage channel which has a relatively flat topography, the rapid development of housing in the floodplain area, the topography of the river in the upstream area has a steep slope so that if heavy rains and high erosion rates causes high peak flows resulting in flooding and erosion, siltation and reduction of river capacity can cause flooding caused by erosion of river beds and river banks due to the absence of vegetation cover, accumulation of sediment in the river sediment deposition causes elevation of the river bed and can reduce the capacity of river channels.Topography greatly influences flood inundation, the lower elevation of the area than the surrounding area often becomes an obstacle to the rate of surface runoff towards the river. Areas on the banks of the river are areas that are most prone to flooding in the event of a river overflow. Areas with a slope of <8% are areas that are difficult to absorb water, such as residential areas with solid pavement, which are more prone to flooding.The aim of this research is to predict the carrying capacity of the river's discharge capacity and provide an overview of flood-prone areas. Design flood discharge, maximum flood discharge and actual river capacity in the KarangMumus sub-watershed return period (years) for the planned flood discharge (Q_rcn) = 578.39m³/s, maximum flood discharge (Q_mak) = 578.62 m³/s, actual river capacity Q = 404.62m³/s, recommended river capacity = 987.85m³/s. Less capacity = 173.77m³/s. So it is necessary to have a recommended river capacity of = 987.85 m³/s. Due to sedimentation of = 0.2198m³/s so that the maximum capacity of the river is =  988.0698m³/s.