Peak Discharge in Jemelak Subwatershed, Sintang District

Jemelak Sub Watershed is close to the junction of two big rivers, i.e. , Kapuas and Melawi. Therefore, this location faces environmental issues such as a flood. To avoid its possible damages, information o n  peak discharge becomes critical ,  particularly  in calculating the drainage structure. This study was aimed to predict the peak discharge in this area using a rational method. The maximum daily rainfall data from 1998 to 2017 were divided into two  periods of 10 years and analyzed. In the first period,  maximum rainfall range s from 98.6 to 176.3 mm, while the second period fluctuates from 67 . 6 to 190 mm. Analysis of land cover described that 43.97% of secondary swamp forest s turned into shrubs and swamp shrubs in the first period. Furthermore, about 800.71 ha of secondary swamp forest tuned into 582.80 ha of bare land, 181.04 ha of a plantation, and 36.88 ha of swamp shrubs in the second period. About 95.15% of shrubs w ere  also turned into agricultural land mixed with shrubs in the second period. The result showed that the changes in the maximum daily rainfall and land cover simultaneously affected the improvement of the peak discharge by about 2.53% in the first period and 28.30% in the second period. If the peak discharge exceeds the river capacity, then the local flooding will occur along the river border. Keywords: land cover, peak discharge, rainfall, Jemelak