Study of the Effect of River Basin Morphology Change on Threshold Parameters in Cimahi Flood Early Warning System

EasyChair Preprint 338

Abstract

Flood early warning systems are used for flood disaster preparedness to reduce disaster risks. The problem that happened was flooding but the warning alarm did not ring. For threshold rainfall parameters, floods occur before the precipitation reaches the threshold limit. The purpose of this research is to determine the influence of river basin morphology change on threshold parameters in flood early warning system. There are 15 cross-sections of the river that are used scattered in the upstream, midstream  and downstream areas of Cimahi river basin, and then one of the cross section of the river is determined as a threshold. The measured hydraulic parameters are the flow depth, flow velocity and the slope of the river bed. The land cover analysis was conducted using the Cimahi river basin land use map to determine the runoff coefficient. The results of this study indicate that the morphological changes of the watershed significantly influence the parameters of the threshold. A 0.5 m rise in river water level can reduce river capacity by 14.3% and narrowing of the 2 m-wide river border lowers river capacity by 11.6%. If it occurs at the same time as the rise of the river basin as high as 0.5 m and the narrowing of the 2 m wide border then the decrease of river capacity up to 35%. The runoff coefficient affects linearly to direct runoff discharges. An increase of the drain coefficient of 17% increased the direct runoff rate by 17%. If the change occurs simultaneously ie the elevation of the river basin as high as 0.5 m, the narrowing of the river border by 2 m and the increase of drain coefficient of 17% then the river capacity will decrease by 45%. Reducing this river capacity makes the threshold parameters in the flood warning system invalid causing flood events can not be detected early by the system.

Keyphrases: Flood Early Warning System, Threshold Parameters, runoff coefficient, water level, watershed morphplogy

@booklet{EasyChair:338,
  author    = {Ariani Budi Safarina and Iin Karnisah and Ade Sena Permana},
  title     = {Study of the Effect of River Basin Morphology Change on Threshold Parameters in Cimahi Flood Early Warning System},
  howpublished = {EasyChair Preprint 338},
  year      = {EasyChair, 2018}}