Final answer:
Yes, both constructing levees and maintaining sand dunes are effective flood hazard mitigation measures. Levees act as barriers to contain rising waters, while sand dunes serve as natural protective buffers against storm surges and flooding. Additionally, sandbags can be used to effectively stop leaks in levees by balancing water pressure.
Step-by-step explanation:
Constructing a levee and maintaining sand dunes are indeed considered flood hazard mitigation measures. Both of these strategies play a crucial role in reducing the risk and impact of floods. Levees are engineered structures designed to prevent overflow from rivers and other water bodies, while sand dunes act as natural barriers that absorb the energy from storm surges and help prevent coastal flooding.
Levees work by providing a physical barrier to contain rising water levels, protecting the land behind them. Maintaining sand dunes involves preserving or restoring these natural features which can buffer against storm damage and rising sea levels. Efforts to maintain and enhance dune systems can include planting vegetation to stabilize the sand or creating dunes using dredged material, in addition to other beach nourishment techniques.
In the case of sandbags being used to stop the flow of water under a levee due to a leak, they create a temporary levee that can balance the pressure of the water on both sides. The small volume of water inside the sandbag column does not need to match the larger body of water behind the levee in quantity; it just needs to exert an equivalent pressure to prevent water from flowing through the leak.