Predictions of Vulnerability Flood and Flood Prone Areas in Watershed West Sumatra Province using Arc-GIS and Category Value

Daoed, Darwizal and Rusman, Bujang and Istijono , Bambang Istijono and Hakam, Abdul (2016) Predictions of Vulnerability Flood and Flood Prone Areas in Watershed West Sumatra Province using Arc-GIS and Category Value. international Journal of Earth Sciences and Engineering, 09 (03). pp. 274-279. ISSN 0974-5904

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Abstract

WestSumatra is an area of west coast of Sumatra; the topography is hilly to steep. It consistsof 20 small watersheds with the area from 20 km2 to 690 km2. The annual rainfall is approximately 4950 mm / year or 340 mm / month(BWS,2008). The area along the coast and estuaries are often vulnerable by flooding. Based on this phenomenon, it can be predicted thatthe flooding in the west Sumatra is caused by the combination of extremely heavy rainfall, length of the rivers which are mostly short and tides. The morphologically rivers that are relatively straight with many branches on the upstream side of the river also cause the situation getting more vulnerable. Flood vulnerability assessment and areas prone to flooding assessment was performed using the results of the land area of the satellite image map, Arc-GIS and hydrological data. The analysis was conducted by using quantitave approarch to categorize and give dignity/values for each parameter that causes flooding. Data were collected from local government and field measurements. The classification of vulnerability was divided into five categories. According to the three watersheds, it was obtained the value that shows the characteristic with rather vulnerable and medium level to flooding and flood-prone areas. It is more dominant determined by rainfall, land use, specific discharge, and the influence of the coast and the existence of waterworks. If the rain occurs at the upstream of watershed at the same time with the rising of sea levels (tide), then there will be inudation due to the stagnant of drainage network systems where the city crosses. It happened for those watersheds of West Sumatra, for small watershed with area more vulnerable in the appeal of a large watershed. Therefore, an integrated flood management plays important role on this particular areas.

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