A strategy is a collection of actions that if implemented together, can reduce the risk of damage during a weather event or crisis.
Government at all levels may have the opportunity to construct and install relevant infrastructure to help control, retain or divert flood waters during a flood event.
Available options to better protect communities include:
- construction of dams
- construction of permanent or temporary levees
- construction of retarding and detention basins
- construction of barrage walls
- installation of flood or tidal gates in stormwater drainage channels
- systems to control or divert flood waters away from low laying areas.
Unregulated flood events tend to be more damaging and can endanger many houses in a community.
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Actions
A levee is a wall designed and built to block water. This prevents flooding in areas that must remain dry.
Sandbags are an example of a small temporary levee. More advanced temporary levees are built from rock, soil, clay and sand. These are professionally moved and often from the area. It can be a lower-cost option for flood mitigation.
Local Governments may have more structured approaches to levees, including using pre-built flood barricades. An example is in Maryborough
The primary purpose of most Australian dams is to ensure a secure water supply. These dams don't have enough excess storage capacity to significantly reduce a flood threat.
Flood mitigation dams are designed to absorb some of the flood volume.
For best effect, the dam needs to:
- have gated spillways
- be sited near the area to be protected
- be operated primarily as a flood mitigation dam
Resources
Floodgates may be permanent or portable. They can be effective in controlling rising flood waters, tidal waters and storm surge. Floodgates may be opened to allow access through levees, for example, and closed when threat levels are elevated. Floodgate systems may be automated or operated manually.
Detention basins temporarily store flood water run-off during flood events. They allow for the release of stored flood water in a controlled manner. Examples include through an outlet structure (drainage pipes). This can reduce peak flows of water downstream.
A levee is a wall or embankment designed to block water from flooding into areas that need to remain dry. Levees are often an economically effective method of reducing riverine flooding in towns.
Levees have a design limit. This usually doesn't exclude the probable maximum flood (PMF). It's likely that flood waters will rise above the levee at some stage.
Special consideration is needed where infrastructure such as roads or railway lines cross permanent levees.