Analysis of Surface Flow Rate (Runoff) on Land Use Case Study in Loa Bakung Sub-District

Abstract— This study aimed to analyze the runoff rate on land use in the Loa Bakung Village. The results of this study are expected to be the basis for flood management in the region. The research was carried out from February - April 2021 at the Water and Soil Conservation Laboratory, Faculty of Agriculture, Mulawarman University. The object of this research is the land use of the Loa Bakung sub-district. The stages of conducting research are as follows: (1) preparation, (2) field observations, (3) data collection, (4) data processing, (5) interpretation, and (6) reporting. The data collected is in the form of; (1) an Administrative boundary map of the Loa Bakung sub-district, (2 Topographical maps, (3) Soil type maps, (4) Loa Bakung sub-watershed maps, and (5) Maximum rainfall data for the last ten years (2011-2020). This is done by calculating the surface flow rate using the rational method. The results showed that: (1) The results of the GIS analysis showed that there were five types of land use in Loa Bakung Village, namely shrubs, settlements, roads, mining, open land, and dry mixed agriculture. The use of shrubland has the largest area of 481.34 hectares, and the smallest is land without vegetation, namely 27.18 hectares; (2) The highest runoff coefficient (C) is in the use of shrubland, namely 0.13463. While the value of C or the smallest runoff coefficient is on the use of open land with a C value of 0.00493; and (3) The maximum runoff rate (Q) in the land use of Kelurahan Loa Bakung occurs in the 100-year return period (Q100) with a value of 157.4292 m3/sec and the lowest Q value appears in the five year return period (Q5) with a deal 86.1099 m3/sec.