Which of the following is NOT considered a main cause of flood damage?

The correct choice identifies thermal damage as not being a main cause of flood damage. In flood situations, the primary factors contributing to damage are related to water's physical properties and effects. Hydrodynamic forces refer to the powerful impact of moving water, which can cause structural damage and erosion. Soaking encompasses the saturation of soil and materials with water, leading to structural instability and additional forms of damage over time. Sediment and contaminants in floodwaters can cause significant health hazards and deterioration of buildings and infrastructure when deposited as floodwaters recede.

In contrast, thermal damage typically refers to issues caused by extreme temperatures and is not directly related to flooding. While thermal conditions can affect materials in general, they are not a primary driver of damage in a flood context. Therefore, this distinction elucidates why thermal damage does not belong in the context of main causes of flood damage.