Utilizing NDWI, MNDWI, SAVI, WRI, and AWEI for Estimating Erosion and Deposition in Ping River in Thailand

Abstract

The Ping River, located in northern Thailand, is facing various challenges due to the impacts of climate change, dam operations, and sand mining, leading to riverbank erosion and deposition. To monitor the riverbank erosion and accretion, this study employs remote sensing and GIS technology, utilizing five water indices: the Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI), Soil-Adjusted Vegetation Index (SAVI), Water Ratio Index (WRI), and Automated Water Extraction Index (AWEI). The results from each water index were comparable, with an accuracy ranging from 79.10 to 94.53 percent and analytical precision between 96.05 and 100 percent. The AWEI and WRI streams showed the highest precision out of the five indices due to their larger total surface water area. Between 2015 and 2022, the riverbank of the Ping River saw 5.18 km2 of erosion. Conversely, the morphological analysis revealed 5.55 km2 of accretion in low-lying river areas. The presence of riverbank stabilizing structures has resulted in accretion being greater than erosion, leading to the formation of riverbars along the Ping River. The presence of water hyacinth, narrow river width, and different water levels between the given periods may impact the accuracy of retrieved river areas.