General geology and a study on characteristics of Betis River, Kuala Betis, Gua Musang.

A study of general geology and river characteristics were done in Kuala Betis area which covers 25 km². The aim of this study is to produce geological map of l:25000. Next, this study is conducted to identify the characteristics of Betis River as well as to correlate between the characteristics with the catastrophic flood that occurred in Kelantan last year. Based on the result of geological mapping, the study area composed of two different formation which are Gua Musang formation and Karak Formation which belong to Bentong Group. Gua Musang Formation covers three types of lithology unit which are argillaceous, limestone, and conglomerate. The argillaceous unit composed of shale, mudstone and siltstone. This Gua Musang Formation is predicted to be age from Permian to Triassic. While the other lithology unit was assumed as Karak Formation which is the quartzite unit. This quartzite unit is the oldest lithology that can be found in study area, assumed age as Devonian period in Middle Palaeozoic. The quartzite unit together with conglomerate unit covers some parts of western part of study area, the middle part is covered by limestone unit and the remaining part was mostly covered dominantly by argillaceous unit. The study river characteristics covers 9.39 km of Betis River, which divided into ten station. By using combination of HEC-RAS 4.1 and ArcMap 10.2, all the characteristics of Betis River were irregular trend from upper stream to downstream. The correlation between those characteristics indicates that the river depth was inversely proportional to its width, while the river velocity and cross sectional area were directly proportional to its width and discharge respectively. Based on the daily rainfall data, there was a maximum volmne of rainfall measured as 3.896 m²during 22 December 2014. Continuous this amount of rain lead to the overflow of water in Betis River and caused flood at Kuala Betis on that time.