Riverbank retreat analysis of the U-Tapao River, southern Thailand

Riverbank retreat is a result of complex combinations of several processes, including subaerial processes, fluvial erosion, and bank failure. The objective of this study was to analyze riverbank retreat of six representative riverbanks along the U-Tapao River in southern Thailand using a process-based riverbank retreat model. Field and laboratory tests were conducted to determine index and engineering properties of the riverbank soil required in the modeling. In particular, the erodibility parameters of the riverbank soil were estimated using empirical formulae, measured in situ by performing a submerged jet test, and estimated from long-term bank retreat simulations using the Bank Stability and Toe Erosion Model (BSTEM) incorporated with a lumped adjustment factor. The observed bank retreat over the period from 2002 to 2016 obtained from analysis of aerial imagery was used to verify the validity of the riverbank retreat results. Good agreement with the observations was obtained from BSTEMs using adjusted erodibility parameters.