Quantifying the Effects of Water Management Decisions on Streambank Stability

Abstract Both natural processes and human activities alter streamflow conditions, which can significantly affect streambank erosion and stability, leading to negative consequences including sedimentation of reservoirs, contamination of streams, loss of productive land, and damage to infrastructure. Hydrological conditions, which are often controlled by water management infrastructure (e.g., reservoirs and dams) and decisions, are a major factor affecting streambank erosion and stability. While significant research has studied the relationships between hydrology and water management, as well as hydrology and streambank stability, there is little research that considers the connection between water management and streambank stability. The objective of this work is to develop a module to investigate how water management decisions, particularly reservoir operations, affect streambank stability. A module was developed to estimate streambank stability using a factor of safety approach, with hydrologic conditions derived from an established integrated hydrologic model. This module is validated and then demonstrated using integrated hydrologic model results from the Lower Republican River Basin in Kansas, USA. Results applied to this basin indicate that several water management decisions, such as groundwater pumping and timing of reservoir releases, may negatively affect streambank stability by changing pore water pressure, the weight of the streambank soil, and the pressure differential between surface and subsurface. Given that most of the rivers and streams of the world are regulated by reservoir operations, this work demonstrates why this water management needs to be considered in simulations of streambank stability.