Module 6: Bank erosion hazard index (Part 2: Water watch programme for young leaders modules)

Abstract

Streams and rivers are formed by natural geological processes, fluvial dynamics, and human disturbance (Sulaiman et al., 2021). As a result, water resources must be carefully managed to ensure the long term viability of river landscapes and a steady supply of clean water. We might notice that the river landscape keeps changing each year after a major flood event. River landscapes are altered due to erosion, sediment transport, and deposition (Julien, 2010). An interruption of natural river equilibrium through land-use change, in-stream sand mining or other causes will result in erosion or deposition downstream of the river networks. We are interested in having a stable channel and river bank which can be defined as the least degraded channel caused by natural and anthropogenic alterations, with the most ecologically and morphologically dynamic states, self-sustaining and resilient to external perturbations (Palmer et al., 2005) and the best condition that the river can balance the human alterations given the catchment conditions (Brierley & Fryirs, 2013). An unstable river bank will lead to excessive erosion, sediment transport and deposition processes. Although these three processes are natural phenomena that shape our river landscape (Julien, 2010), the excessive process will lead to river encroachment, the retreat of the river bank, damaging hydraulic structure and machines as well as shallowing the navigational passage (Vanoni, 2006; García, 2008).