Kajian Stabilitas Lereng Sungai Dodokan Desa Kebon Ayu, Kabupaten Lombok Barat

Abstract

The Dodokan River is a vital river in West Lombok Regency that plays a role in drainage, flood control, and environmental balance. However, hydrological and geotechnical conditions can affect the stability of the riverbanks and trigger landslides. This study aims to determine the geotechnical characteristics of the soil composing the slopes, analyze hydrological conditions such as rainfall and design flood discharge, assess the impact of geotechnical and hydrological characteristics on slope stability, and identify effective mitigation alternatives. The research methodology involved collecting disturbed soil samples from three slope zones: upper, middle, and lower. The samples were tested in the laboratory to determine the physical and mechanical properties of the soil. Subsequently, a hydrological analysis was conducted to determine the design flood discharge, a hydraulic analysis was performed to assess erosion potential, and a slope stability analysis was carried out using GeoStudio SLOPE/W with the Morgenstern-Price method. The results of the study indicate that the soil composing the slope is classified as coarse-grained soil with cohesion values ranging from 0.814 to 7.590 kPa and internal friction angles ranging from 22.36° to 39.02°. The design flood discharge for a 25-year return period of 136.315 m³/s with a flow velocity of 2.372 m/s has the potential to increase scouring at the base of the slope. The Factor of Safety (FoS) for the existing conditions is 1.913 under dry conditions but decreases to 1.047 during a flood. After the landslide, the FoS was 1.752 under dry conditions and 0.979 during flooding. Remediation using a combination of riprap, regrading, geotextiles, and surface drainage increased the FoS to 2.556 under dry conditions and 2.068 during flooding. This combination effectively improved slope stability and is recommended as an alternative for addressing landslides along the Dodokan River.