Applying water sensitive urban design to new development

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When it rains stormwater flows into our waterways untreated off our urban landscape.

Before the land was developed, rain would have soaked into the ground and nutrients like nitrogen that occurs naturally in rainfall would have been used up by the vegetation.

Hard surfaces in urban areas including roofs, roads and pathways cause an increase in runoff fast tracking a variety of nutrients directly into our waterways picking up additional pollutants such as sediments, petrochemicals, faecal coliforms, and heavy metals along the way.

When nitrogen is in excess in our estuaries it fuels algal blooms. Too much algae reduces the amount of light reaching seagrass, limiting its growth.

Seagrass is the basis of the estuary food web and is very important habitat for fish and aquatic bugs, it oxygenates the water. Compared to algae, seagrass is long lived and when algae decompose oxygen from the water body is consumed resulting in low oxygen conditions, impacting on the health of aquatic life.

Sediment from the land smothers seagrass, clogs the gills of fish and aquatic bugs.

When the condition of the aquatic environment is compromised its inhabitants become stressed and are more prone to disease causing issues such as red spot in fish.

Our community value the waterways and they not only support our lifestyle but also a thriving fishing, oyster growing and tourism.

Council is focused on protecting waterways from the effects of urban development through the implementation of a water sensitive design policy that makes up part of the Development Control Plan (DCP).

This policy requires all new developments to design and install water quality treatments such as raingardens and water tanks to help filter nutrients and sediment out of stormwater before it enters our waterways.

In large developments like subdivisions, there is a target in the DCP to ensure that there are no new impacts on our waterways this is called a neutral or beneficial effect target. Since 2015/16, 26 large subdivisions have achieved the ‘no new impact’ target. In the 2018/19 financial year 4 large subdivisions across the MidCoast region and an additional 10 large developments such as commercial, industrial and multi dwellings have also been assessed.

Small scale, infill developments such as single dwellings are also included in the DCP providing further protection from nutrient and sediment input to our waterways, these controls are only applied to the Great Lakes region. Since 2015, 596 individual houses have been approved that were required to address water sensitive design. It is estimated that by reducing pollutant loads to the required standard on these lots through raingardens, swales and rainwater tanks we have prevented 147 kg of total nitrogen and 18 kg of total phosphorous from being washed into our waterways annually. In addition to the nutrient reductions, it is estimated that 9 tonnes of sediment has been intercepted by these water quality treatments on single dwellings each year.

These figures are considered to be conservative as additional nutrient and sediment removal will be achieved on the dual occupancies and other developments such as commercial and industrial development during this time frame.

Council have continued to refine the water sensitive design section of the DCP to ensure that developments are utilising best practice methodology and providing the best possible water quality outcomes.

Improvements have included simplifying the water sensitive design chapter of the DCP and establishing a wider range of standard drawings for single dwellings, mapping the location of priority areas and pre-existing stormwater strategies, education materials and guidelines.

As a result of these improvements customers have clear information on what water quality information needs to be prepared for development application.

These improvements resulted in MidCoast Council receiving the National Stormwater Award for Policy or Education in 2018.

For further information on how to apply these conditions in your development click here.

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