Introduction

Basic Nature and Potential Hazard and Risks of a Flood

Flooding is the costliest and most common natural disaster in the history of the United States. Florida is especially vulnerable to flood disasters because of its 1,350 miles of coastline, countless rivers, and abundant floodplain areas. Public awareness of the flood threat in Florida is evident, as Florida residents and businesses now hold more than 40 percent of all flood insurance policies in the nation.

Other parts of the country susceptible to flood include:

• Coastal areas from Texas to Florida and Georgia to Maine.

• Mississippi River

• Other

Flood Basics

A flood is a general and temporary condition of partial or complete inundation of normally dry land areas from one of the following four sources:

• The overflow of inland or tidal waters.

• The unusual and rapid accumulation or runoff of surface waters from any source.

• Mudflows, which are primarily caused by floods, as defined above, and are akin to a river of liquid and flowing mud on the surface of normally dry land area, as when earth is carried by a current of water and deposited along the path of the current.

• The collapse or cave-in of land along the shore of a lake or other body of water as a result of erosion or undermining caused by waves or currents of water exceeding the cyclical levels which result in flood, as defined above.

Types of Flooding

There are two fundamental types of flooding: riverine flooding and ocean flooding.

• Riverine flooding occurs when rivers and streams overflow their banks, due to extensive rainfall. When the amount of water being carried by a river or stream exceeds the capacity of its channel, the water overflows onto the adjacent land. The land that is most likely to be flooded is commonly referred to as the floodplain.

• Ocean flooding affects coastal areas. Beachfront properties are particularly vulnerable. Areas around bays and adjacent to streams that empty into bays near the coast are also at risk. Ocean flooding is caused by tropical storms and hurricanes due to the high winds and reduced atmospheric pressure associated with these storms. Reduced atmospheric pressure causes the level of the ocean to rise, effectively moving the shoreline further inland. This rise in the mean elevation of the ocean in localized areas is referred to as storm surge.