Which of the following interventions could prevent coffins from being displaced in flooding events?

Implementing better drainage systems is the most effective intervention to prevent coffins from being displaced in flooding events. Proper drainage systems can significantly reduce the risk of excessive water accumulation in cemeteries, which is a primary concern during flooding. By managing and directing water away from burial sites, the integrity of the graves can be preserved, preventing soil erosion and the subsequent displacement of coffins.

While using heavier materials for coffins might provide some deterrence against floating, it does not address the root issue of water accumulation and flooding. Similarly, increasing the cost of burial plots and encouraging immediate cremation also do not solve the problem of existing burials being endangered during floods. By focusing on improving the drainage infrastructure, the potential hazards associated with flooding can be better mitigated, ultimately safeguarding the gravesites and their contents.