What is to be gained by digging a drain?
Sometimes community members take matters into their own hands and dig a drain from an estuary to the sea in an attempt to lower the water level or improve water quality. Unnaturally draining a river by digging a channel to the ocean can cause large numbers of fish to die, can disrupt fish and bird breeding cycles and can have a negative impact on the plants that grow in and beside the river. Even if it looks like the water quality is poor, if a river is unnaturally opened to the sea, it can make the water quality even worse. The river mouth often closes again quickly leaving smelly, unpleasant water behind.
Some estuaries naturally open and close to the sea due to variations in river flows and ocean forces. These rivers rise when sand blocks their path to the sea. The management of each estuary closure requires careful consideration because of the many competing interests and land uses in and around an estuary.
Sometimes the difficult decision is made by government agencies, local government or emergency services to artificially open an estuary. This is done to prevent or respond to a flood emergency that threatens people’s safety or property as there may be critical infrastructure, dwellings and critical access roads at risk of being inundated. As the sea level continues to rise over the coming decades, more land and assets will become inundated more frequently and it will become increasingly difficult to safely open estuary entrances out to the sea. Catchment Management Authorities across the state are working with agencies, local government and communities to remove, raise or modify these assets so that estuary mouths can open and close without human intervention.
It is important to remember that natural flooding influenced by an estuary closure has many ecological benefits. It is a crucial process that maintains and improves the health of ecosystems providing essential habitat and food, while facilitating nutrient exchange and improving soil health. Flooding due to estuary closures is often termed “blue-sky flooding” because it can happen when rainfall and freshwater inflow is low and other parts of the landscape are dry. This is why estuaries can play a critical role as drought refuges for wildlife when inland water bodies have dried up.
If you observe a suspected illegal estuary opening, please notify your EstuaryWatch coordinator as soon as possible. For more information on the known adverse environmental impacts of manually opening an estuary with an excavator or shovel, check out this resource developed by Corangamite Catchment Management Authority and Lloyd Environmental