Читать книгу Disaster Response and Recovery - David A. McEntire - Страница 27

Hydrologic hazards are closely related to atmospheric hazards and these agents have a specific impact on the earth’s water systems. There are several types of hydrologic hazards, one of them being floods. Floods are the most prevalent of any hazard around the world and in the United States—whether natural or otherwise. They are also among the costliest. Episodes of flooding occur when there is too much precipitation or where

there is an inability for soil to absorb water that has fallen to the ground. Flooding can also result from melting snowpack and ice jams. Soil type, topography, deforestation and level of development all have bearing on flooding. For instance, clay soils are more likely to produce runoff in comparison to sandy soils. Hills, valleys, and the use of cement or asphalt on streets and parking lots in highly urbanized areas may also contribute to this type of hazard.

The 1993 great Midwestern flood is the most widespread and costly flood in U.S. history. Months of unusually wet weather and the seasonal snowmelt overwhelmed the Mississippi River Basin with water. Dykes, locks, and dams were eventually filled to capacity, and many of them were breached. The water emitted from broken levees only added to the flooding downstream. Thousands of people had to be evacuated and property losses totaled in the billions of dollars.