Establishing Geomorphic Reference Criteria for Design of River Diversions Around Mine Pits in the Pilbara, Western Australia

Abstract

The poor condition of river diversion channels can prevent mining companies from relinquishing their mine to the government after mining has ceased. Many regions lack a locally derived template for integrating appropriate geomorphic and hydraulic conditions from unmodified river channels into river diversion designs to help guide post-mining closure activities. Establishing baseline geomorphic reference criteria for unmodified catchments can guide restoration efforts to allow recovery and stability of the fluvial system. Design-wise, channels should be built so that flow conditions are able to move sediment, but not high enough to accelerate erosion in the channel. We used natural headwater channels to inform a regional guide for geomorphic criteria for artificial channels constructed in the Pilbara, Western Australia. We provide guideline hydraulic criteria for specific channel types, including velocity, stream power, and bed shear stress values for five key channel types: alluvial single thread (≥ cobble) and single thread (sand), bedrock/confined channel sections, island-barform channels, and heavily vegetated channels.