ANALYSIS OF CHANGES IN DISCHARGE AND FLOOD POTENTIAL AND CHANGES IN THE MORPHOLOGY OF THE TRUNEN RIVER DUE TO THE DEVELOPMENT OF THE IKN AREA, PENAJAM PASER UTARA DISTRICT

• Main Author: Harya Wisanggeni, Dimas
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87219
• Institution: Institut Teknologi Bandung

Driven by critical conditions in the capital city of Jakarta such as traffic congestion, land subsidence, pollution, flooding, and increased population density, in 2022 the State Capital Law has been enacted regarding the relocation of the capital city of DKI Jakarta to the Capital City of the Archipelago (IKN) in Penajam Paser Utara Regency, East Kalimantan. As a result, in the next few years the watershed area in IKN will experience land use change, especially in the Trunen River, Trunen Sub Das. This study discusses the effect of land use change due to the construction of the State Capital of the Archipelago which results in changes in flood discharge so that it is necessary to research the effects of moving the state capital and minimize negative effects if they occur such as potential flooding. The analysis carried out includes hydrological analysis, tidal analysis and hydraulics analysis. Flood Discharge Modeling using HEC-HMS with Qbankfull discharge calibration. Flood modeling using HEC-RAS dmodel 1-D and 2-D using 100-year return period discharge as upstream boundary and tidal HWL as downstream boundary of modeling. Sediment modeling was conducted with quasi unsteady flow and sediment rating curve at the upstream boundary and tidal hydrograph as the downstream boundary. Flood and sediment modeling was carried out with several scenarios of combinations between discharge, geometry and flood control buildings in the form of retention ponds, normalization, embankments and groundsills. The output produced in this research is the effect of land use change due to the construction of IKN on flood discharge, flow velocity, and how riverbed changes occur before and after the existence of flood control structures. Based on the results of the modeling, the land use change resulted in a change in CN value from 78.3 to 83.9 as well as a change in the 2-year return period flood discharge from 67.6 m3/s to 83.4 m3/s and a change in the 100-year return period flood discharge from 270.1 m3/s to 301.8 m3/s. In flood modeling a return period of 100 years is used and there is an average runoff between 0.5-2 m in existing conditions. In sediment modeling there is an average degradation of 15.8 cm/year. From these results, an alternative of building 1 retention ponds, river normalization and widening, embankments, 6 groundsills was proposed and was able to reduce the average water level by ± 31 cm, reduce the average flow velocity by ± 0.36 m/s, reduce the average degradation of the riverbed by ± 13.4-13.9 cm/year and reduce the erosion rate by ± 2.42 tons/day. The results of this study are expected to be a reference for stakeholders in making decisions related to flood management and sedimentation/erosion in the Trunen River so as to reduce the negative impacts that may occur in the region.