The response of alluvial streams to floods is often unpredictable. Knowledge of the history of a stream and its response to floods is the best guide for determining the extent of flood damage prevention measures. When protection is needed, whether at the time of construction or at a later date, the cost of providing the control measures should be compared to the potential costs associated with flood damage without the prevention measures.

Flood-related damage results from a variety of factors including the following:

The designer should assess the potential for these and other conditions to occur and consider measures that reduce the potential for damage from flooding.