Final answer:
Conservation of wetlands and preservation of natural forests are two passive strategies to mitigate flood risks, acting as buffers against storms and floods, and reducing flood frequency and severity.
Step-by-step explanation:
Name two passive strategies for avoiding flood risks: Conserving wetlands and preserving natural forests are two effective passive strategies. Wetlands act as natural buffers against storm surges and floods. Studies have shown that areas stripped of mangrove forests experienced more severe impacts from events like tsunamis. Similarly, natural forests have been found to reduce flood risks and the severity of floods. A 10% decrease in natural forest area can lead to a significant increase in flood frequency and duration, demonstrating the importance of forest cover in managing flood risks.