Using directly connected imperviousness mapping to inform Stormwater management strategies

Directly connected imperviousness (DCI) has been established as a catchment indicator of waterway ecological condition, and waterways with DCI above 2% have been shown to be in poor ecological condition. As a result, stormwater management needs to be undertaken to ensure a more natural hydrological cycle is maintained. Melbourne's rapid growth means there is increasing imperviousness in many areas. This is especially concerning where waterways are currently in excellent condition. Whilst protection of 'the best' is an important aspect of stormwater programs, restoration efforts are also required to achieve long-term goals. To ensure that limited budgets are spent wisely, an approach is needed to target catchments where management effort will produce the greatest returns. To this end, Melbourne Water in conjunction with partners has undertaken two related projects. Both use a DCI dataset in conjunction with a multi-criteria analysis to take into account other factors that influence river health and the efficiency of restoration/protection efforts. This paper presents an overview of these projects, providing an insight into the way they are informing stormwater management strategies.