Environmental watering

Delivery of environmental water is undertaken by water corporations in consultation with the catchment management authorities (CMAs) and DSE. Operating rules include provision for flooding so that when high rainfall events are forecast, water corporations ensure environmental flows are reduced, so as to not exacerbate flooding.

The release of environmental water did not contribute to the recent major floods in Victoria in 2010 and 2011, because the high rainfall events were forecast by the Bureau of Meteorology and environmental flows were subsequently reduced so that they would not contribute to major flood peaks. Environmental watering was resumed after major peaks had passed.

Impact of vegetation

In major floods flood height is controlled primarily by the intensity and amount of rainfall. Vegetation only has a minor effect, as most floodwaters are conveyed in the adjacent floodplain, and not the natural waterway encompassing  the bed and banks of the water course. In fact vegetation.within and along riverbanks can have a beneficial effect on flooding in lowland areas as it slows the rate of water movement within the waterway, reducing erosion.

However, willows can have an adverse affect on the stream environment. Willows invade the bed and banks of streams, reducing the size of the waterway. This reduces the capacity of the stream to carry flood waters. The result is that willows increase the height of flood waters in small and moderate sized floods.

The Victorian Government has invested in willow management through the catchment management authorities (CMAs). The CMA willow removal programs are decreasing flood risk and also improving waterway health across Victoria.