Riverbed Erosion Analysis of Winongo River Using HEC-RAS 5.0.7

Abstract

Winongo River originates from small rivers on the slopes of Mount Merapi. This creates potential debris floods that will carry material such as sand and gravel, which can cause erosion and sedimentation in rivers. Riverbed erosion is the process of transporting materials on the riverbed that causing the elevation on the riverbed to fall. If the riverbed elevation decreases, it will cause the retaining wall building to become unstable and collaps. If this happens, it will have a negative impact on the people who live along the riverbanks. The impact of erosion and erosion analysis at the bottom of Winongo River is carried out using HEC-RAS 5.0.7. There are 200 cross-sections that had been analyzed. The analysis reveals that the locations have the potential of erosion on the riverbed and the damage that can occur in the riverbank. From the results of the analysis that have been carried out using the 2-year return period (Q2), there are erosion in 9 cross-sections on Winongo River which is located in Bambanglipuro District and Jl. Parangtritis. The depth of erosion that occurs reaches 0.96 m in the cross-section WN 173. The erosion causes damage to the retaining wall, such as cracks, flattening, and collaps.