Most clay minerals are hygroscopic, meaning they have a tendency to absorb moisture. As the water table naturally fluctuates with local precipitation, the soil beneath a home or other building may shrink or swell depending on the amount of clay within it. If the soil contains a large amount of expansive clays, damage may occur to the structure, especially in times of heavy rainfall or drought.
Florida has unique origins. What would become the basement rocks of Florida were once part of other continents. Most of Florida's geological history occurred under the ocean, which explains why our entire state has hundreds to thousands of feet of limestone beneath it! The sands and clays at land surface were transported to Florida, via rivers and marine currents, from the Appalachian Mountain belt as it eroded over millions of years.
Geologic hazards (or "geohazards") come in many shapes and sizes. They are hazards because of the unique geologic or environmental conditions of the area.
1. Large amounts of rain over a short period of time where stormwater drainage is insufficent. This is called a flash flood. Water rise may be sudden and with little warning. Additionally, after periods of drought, the soil can be too dry to sufficently absorb the water in the short term (due to the lack of cohesion).
2. Large volumes of water over an extended period. This type of flooding will occur over the long term of the storm, and the flooding may continue long after the storm passes. There will oftentimes be a lag between the event and the flooding as water moves through the hydrologic system. It may even be an event that did not have heavy rain in your location, but areas upstream experienced significant rainfall.
3. Storm-surge flooding from the wind and waves of hurricanes and tropical stroms which result in the accumulation of excessive amounts of water along the coast. It is a combination of the low pressure of the storm allowing water to rise and the relentless surf pushing water inland faster than it can escape against the same waves back to deeper water.
While hurricanes are Florida’s most obvious flood producers, it is important to realize that heavy rains can cause flooding in Florida at any time of the year and at any place. Flooding may result in the loss of human life and property. Episodes of flooding may be accompanied by contamination of aquifers and water wells in some areas. Floridians should be aware of “boil-water warnings” posted in their local news media. It is vitally important that everyone living in Florida be aware of the potential for flooding and resources available to assist Floridians in dealing with it.
Coastal erosion has both natural causes and causes related to human activities. Gradual coastal erosion results naturally from fluctuations in sea-level and by longshore drift. Ideally the movement of sand functions like a balanced budget. Sand is continually removed by longshore currents moving parallel to the shoreline in some areas but it is also continually replaced by different currents of the same type.
Structures such as piers or sea walls, jetties, and navigational inlets may interrupt the movement of sand as it can become “trapped” in one place by these types of structures. The currents will, of course, continue to flow, though depleted of sand trapped elsewhere. With significant amounts of sand trapped in the system, the continuing motion of currents (now deficient in sand) results in erosion. In this way, human development and construction activities that result in the unnatural trapping of sand have the potential to result in significant coastal erosion over time.
The most severe coastal erosion can occur over a very short period of time when the state is impacted by hurricanes and other severe weather systems as a combination of storm surge, flooding, and wind erode the coast.
The Florida Department of Environmental Protection is the state’s lead agency for environmental management and stewardship – protecting our air, water and land. The vision of the Florida Department of Environmental Protection is to create strong community partnerships, safeguard Florida’s natural resources and enhance its ecosystems.