Application of the Digital Shoreline Analysis System (DSAS) to Assess Riverbank Changes of the Kok River, Mueang District, Chiang Rai Province

Abstract

         In recent years, geologic hazards associated with channel changes such as sediment deposition, erosion, and riverbank collapse have occurred more frequently along the banks of the Kok River. This study aims to assess the trends and rates of riverbank change on both the northern and southern banks of the Kok River within Mueang Chiang Rai District, Chiang Rai Province, Thailand. The study applies the Digital Shoreline Analysis System (DSAS) in combination with Geographic Information Systems (GIS) and multi-temporal satellite imagery from Google Earth Pro (GEP) covering the period 2010–2025. The research workflow begins with selecting GEP images for the study period and georeferencing them to a common coordinate system. The riverbanks are then interpreted and manually digitized on an annual basis, separated into the northern and southern banks. Subsequently, DSAS is used to generate a baseline and transects to compute shoreline-change statistics and riverbank change-rate indicators over time. The resulting outputs are further analyzed spatially in GIS to classify erosion and deposition zones and to identify key high-risk locations. The results indicate that erosion is the dominant process along both banks. The northern bank shows an average erosion rate of approximately 1.06 m/year and an average deposition rate of 0.63 m/year. The southern bank exhibits an average erosion rate of about 1.03 m/year and an average deposition rate of 1.00 m/year, contributing to the gradual expansion of newly deposited areas that develop into mid-channel alluvial flats. The most severe erosion on both banks is concentrated near the Kok River bridge (National Highway No. 131), particularly in Mae Yao Subdistrict and Doi Hang Subdistrict. Overall, the Kok River banks are expected to continue changing, with erosion and bank failure remaining the primary hazards in the study area.