Bank retreat study of a meandering river reach case study: River Irwell

Lack of data is often considered a limitation when undertaking morphological studies. This research deals with morphological studies of small rivers experiencing bank erosion processes when only limited data are available. A reach of the meandering gravel-bed river Irwell (United Kingdom) is taken as a case study in order to analyze the bank retreat process that is endangering the stability of structures located in the area. Two models of different complexity are applied. The first is a physic-based one-line meander model, computing bed topography, flow field and migration rate of meandering rivers in areas with non-uniform erodibility. The second is a 2D physic-based morphological model with a simplified bank erosion formulation. The model predictions show that the morphological development of the river may endanger the existing structures within the next five years, if no mitigation works are carried out. The simple meander model produces satisfactory results in much less time using less data. Moreover it allows taking into account the effect of riparian trees and soil heterogeneity on bank erosion. Besides, the simple meander model appears appropriate for probabilistic analysis of future river migration trends. A particular application of this analysis is the study of climate change effects. The probabilistic analysis will be done in a second phase of the study.Hydraulic EngineeringCivil Engineering and Geoscience