Model application to assess effects of urbanisation and distributed flow controls on erosion potential and baseflow hydraulic habitat

The catchment model SWMM was modified to include on-site flow-control devices, and then linked with models of hydraulic habitat suitability and erosive potential for specific reaches in a study catchment. Urbanisation decreased the modelled baseflow by up to 33% and reduced the area of suitable hydraulic habitat by 0.5-13.3%, depending on the reach and species. Hypothetical infiltration devices increased the baseflow to pre-development levels, with an associated increase in habitat, but other measures were not effective. Urbanisation increased the erosion potential index by a factor of 1.58-9.32, depending on the reach. Erosion-control ponds decreased the erosion potential to pre-development level in some reaches. Detention tanks reduced the erosion potential significantly, but not to pre-development levels. The poor predictive ability of the models for baseflow compromised the utility of the hydraulic habitat assessment. Predictions of the effects of urbanisation on baseflow habitat should therefore be treated cautiously.