SURFACE FLOW DISCHARGE FROM FOREST AREA ON THE UPSTREAM OF CIDURIAN LITTLE WATERSHED, BANDUNG REGENCY, WEST JAVA

• Main Author: Darul Hilmawan, Rofie
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/46676
• Institution: Institut Teknologi Bandung

The upstream of Cidurian little watershed currently only has a forest area of 253.17 hectares out of a total land cover area of 10,616.74 hectares. The unequal allocation between forest area with agricultural land area, which dominates in this upstream area, results in the rain falling in this region mostly flowing into Cidurian river, causing a large runoff discharge in the downstream, in this case is Bandung City. Therefore, this study was conducted to determine the total amount of river discharge from the forest area, both from springs and surface runoff water that flowing into the river when it rains so that a rehabilitation plan in the upstream of Cidurian little watershed can be made to reduce excess river flow discharge to downstream. The data collected in this study include land cover data, Cidurian river discharge, and the amount of runoff water depth. Land cover data is obtained by digitizing the map of upstream area so that a land cover map and its area are produced. Cidurian river discharge is measured at 3 (three) points based on its land cover along the river stream. The runoff water depth is estimated using the SCS method with monthly rainfall data input downloaded every month from the BMKG website. From the digitization results of the upstream area of Cidurian little watershed, the total area is 129.31 hectares, which is divided into 3 (three) parts, namely the first part is pine agroforestry (20.77 hectares), the second part is pine forest with several points of clear land (17.47 hectares), and the third part is agricultural land area (91.07 hectares). From each measurement point, respectively under normal and rainy conditions, the highest river discharge obtained from pine agroforestry was 84.16 m3/day and 135.94 m3/rainy day, in mixed pine forest was 153.1 m3/day dan 360.48 m3/rainy day, and in agricultural area was 588.8 m3/day and 1,044 m3/rainy day. Then the average runoff water depth obtained in pine agroforestry area was 93.6 mm, in mixed pine forest was 134.2 mm, and in agricultural area was 184.4 mm. This shows that the more a land cover exposed, the greater runoff water discharge. The absence of forest vegetation cover reduces amount of water retained above the soil surface, thereby increasing the amount of water that runs off the ground.