Geomorphic flow objectives for the Port Phillip and Westernport region

Urban development leads to a number of physical changes in drainage catchments including increased impervious area, increased hydrological connectivity between hillslopes and streams, and a reduction in infiltration and evapotranspiration. The changes lead to alteration in the flow regime in the catchment that can impact on instream ecosystem health through direct impacts (e.g. reduced baseflow) and indirect impacts (e.g. erosion of riffles that provide instream habitat).

Alluvium was engaged by Melbourne Water to develop geomorphic flow objectives (GFOs) to protect the physical form (i.e. the geomorphology) of receiving streams from changes in hydrology following urban development.

The approach documents a series of analyses undertaken to test the impact of various flow objectives on the erosion potential in a sensitive stream. The purpose of the analyses is to determine whether compliance with those objectives will also protect the geomorphology of receiving if investigate if there is a clear link between geomorphic form and processes and instream ecosystem health.