Flood debit analysis based on land use: A case of Batang Arau Watershed, Padang

Abstract

A flood may occur for both climatology and human action factors. The climatology factors can be in the form of land degradation, land-use changes, and population increase. The land-use changes can identify when there is a conversion of recharge area into a built area. The conversion may happen because there is potency for a flood area to transform into a place of cities development and settlements. When the population increases, space needed also enlarges. Consequently, the surface flow increase and can cause a flood. Padang - Indonesia, has high rainfall intensity around 3,329 to 4,296 mm/year, which results in a frequent flood. The worst flood occurred on 26 September 2018 and 2 November 2018, which washed away a bridge and caused a 3-meter high puddle. In analyzing those phenomena, this study applied a descriptive qualitative method. The image used in the map was analyzed with Argis X quantum program to get a flood-prone map. The rainfall was calculated by using methods of Thiesen, Gumbel, and Log Pearson III, while the debt calculated using the rational method. The difference debit between these was 42,030m3/second. The results, the amount of land used to discharge was higher than due to the rainfall.