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Best Management Practices

FEMA BMP

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Coastal Barrier Resource System Map Panel Information – National Flood Insurance is NOT available to these special vulnerable areas.

Sites in Sarasota County

Coastal Erosion – Coastal flooding and erosion are serious problems along much of the nation’s coasts, although the frequency and magnitude of flooding and the severity of the erosion vary considerably as a result from storm surges and wave actions.

Community Rating System Program – The National Flood Insurance Program's (NFIP) Community Rating System (CRS) is a voluntary incentive program that recognizes and encourages community floodplain management activities that exceed the minimum NFIP requirements.

Community Rating System     
Communities in Florida

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Emergency Plan, Flood-Family Plan  – preparations before, during, and after a flood.

FLASH Floods: Family Disaster Plan

Floods: Assembling a Disaster Kit

Evacuation Zones and Shelters  

Evacuation Shelters and Maps

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Facilitate accurate insurance rating  
See Sarasota County Elevation Certificates; and for retired Flood Insurance Rate Maps and Compliance issues contact Martin Duran, CFM, Planning and Development Services at 941-861-5000

FEMA Flood Maps 
Flood insurance Rate Maps on-line, at www.msc.fema.gov, or at main libraries in Sarasota County; at both North and South County building permit offices; or contact your property insurance carrier.

Federal Flood Map Update Project in Unincorporated and Incorporated Sarasota County

Federal Flood Mitigation Grant information –  visit the FEMA Library - Hazard Mitigation Assistance (HMA) Grant Programs Fact Sheet, or call your CRS Coordinator at 941.861.5000

Flash Flooding is a type of riverine flooding. “Flash flood” is a term widely used by flood experts and the general population. The National Weather Service defines a flash flood as “A rapid and extreme flow of high water into a normally dry area, or a rapid rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (e.g., intense rainfall, dam failure, ice jam). However, the actual time threshold may vary in different parts of the country. Ongoing flooding can intensify to flash flooding in cases where intense rainfall results in a rapid surge of rising flood waters.”^[1]

Flash floods are also characterized by a rapid rise in water, high velocities, and large amounts of debris. Major factors in flash flooding are the intensity and duration of rainfall and the steepness of watershed and stream gradients. Flash flooding occurs in all 50 states, most commonly in steeply sloping valleys in mountainous areas, but can also occur along small waterways in urban
environments. Dam failure, release of ice jams, and collapse of debris dams also can cause flash
floods.[2]

Flood Damage Protection Ordinance

Ordinance No. 2009-60

Flood History

1948	Aerial of Sarasota County – What our topography looked like in 1948.
1950	Hurricane Easy – September 5 Remains the largest 24 hour rainfall total on record for the state of Florida, in Yankeetown at 38.7 inches in 24 hours. Sarasota County Flood Losses.  First landfall, 140 miles north of Sarasota in Cedar Key, FL  Second and final landfall, after making a loop was Homosassa Springs
1962	Flood Event – September 20-21 Average rainfall recorded in six counties was 10 inches over 5,000 square miles. Greatest damages occurred in Sarasota County 58 acres of residential area; 60,000 acres of ranchland; 7,900 acres of improved pastures and 10,700 of woodlands sustained damages. Total $2.3M in damages; one death, 1,000 residences flooded; between 10,000 to 15,000 persons directly impacted. Full report and photos
1982	Subtropical Storm One – June 17-18   Landfall at Springhill, FL approximately 100 miles north of Sarasota. Approximately six inches of rainfall, storm surge and wave action. NFIP flood claims in 2008 dollars: $2.02M  1982 Florida subtropical storm
1985	Hurricane Elena – September 1 Landfall 100 miles south of  Apalachicola, FL. approx 300  miles north of Sarasota. Approx. three inches of rainfall, storm surge/wave action – NFIP flood claims in 2008 dollars: $2.23M
1988	Tropical Storm Keith  – November 23  Landfall Sarasota County at 65 m.p.h.  one to three inches of rainfall, storm surge/wave action. NFIP claims paid in 2008 dollars: $1.21M
1992	Tropical Depression One – June 23 Sarasota and Manatee Counties excess of 20 inches of rainfall NFIP claims paid in 2008 dollars $7.94M
1995	Tropical Storm Dean – July 18 9-11 inches rainfall. Landfall in Texas. NFIP Claims paid 2008 $2.20M
1996	Tropical Storm Josephine – October 4-8 The origin of Josephine did not appear to be directly related to a tropical wave but stalled over the southwestern Gulf of Mexico and made landfall in the eastern Appalachee Bay Florida as a 60-knot tropical storm. Sarasota County NFIP Flood Claims Paid $894,844.45
1997	November 14 – un-named storm.  No national reports. 10 inches of rainfall in Sarasota County.  NFIP claims paid in 2008 dollars: $3.58M
2001	Hurricane Gabrielle – September 14 Landfall Venice, FL at 70 mph downgraded to storm.   5-10 inches of rainfall, storm surge/wave action. NFIP claim paid in 2008 dollars: $2.95M
2003	Storms April through July – June 23  8-10 inches of rainfall.  Myakka River received most from north-overbanks and floods out 41 residences. Waters do not receed for over 30 days. Some heights of water recorded at 18 ft.  NFIP claims paid in 2008 dollars: $3.06M
2004	Hurricane Charley – Aug 13 Landfall Punta Gorda, FL    Hurricane Frances – Sept 6 Landfall Hutchinson Island, FL .  Three to seven inches of rainfall.  NFIP in 2008 dollars paid: $.34M.  Hurricane Ivan – Sept 16 Landfall Gulf Shores, AL. Hurricane Jeanne – Sept 25   Landfall 2 miles of south of Hutchinson Island, FL.

Floodplain Management Plan – available on Sarasota County Emergency Services
Sarasota County floodplain management plan 2009 Update

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Grant Mitigation Assistance – see the federal flood mitigation grant fact sheet

FEMA Hazard Mitigation Assistance (HMA) Grant Programs Fact Sheet
More information is available at FEMA Hazard Mitigation Assistance Programs and FEMA Flood Mitigation Assistance (FMA) Program  

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Local Mitigation Strategy Plan – see Sarasota County Emergency Services: Local Mitigation Strategy Documents

Level of Service for Structure and Street Flooding 

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National Flood Insurance Program – Sarasota County adopted regulations in 1971 and received the first Flood Risks Maps in 1972.

FEMA NFIP
FloodSmart.gov

NFIP Reform Congress has requested reform – review the three phases of progress

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Overbank Flooding
One of the common types of Riverine Flooding. Overbank flooding of rivers and streams – the increase in volume of water within a river channel and the overflow of water from the channel onto the adjacent floodplain – represents the classic flooding event that most people associate with the term “flood.” In fact, this is also the most common type of flood event. Hundreds of riverine floods, great and small, occur annually in the United States.

P

Prepare a Plan – Be prepared before a flood, during a flood and after a flood 

Federal Alliance for Safe Homes

Promote awareness of flood insurance – Contact your Community Rating System Coordinator at 941-861-5000 or email Floodmapupdates@scgov.net for speakers or other outreach activities scheduled.

Beginning in March 2011 through October 2012, staff will be available for two hours each at the following libraries: Elsie Quirk; Fruitville, Jacaranda, North Port and Selby.

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R

Rainfall, Real-time and historical data - Sarasota County has fifty-four Automated Rain Monitoring Sensors (ARMS) strategically located in Sarasota County. This real-time and historical data can be viewed on-line:

Automated Rain Monitoring Sensors (ARMS) 

Reduce Flood Losses best management practices in Sarasota County include but are not limited to land development regulations, flood damage protection ordinance, grant mitigation assistance for individuals, public outreach and education.

Riverine flooding and types defined. The dynamics of riverine flooding vary with terrain. In relatively flat areas, like Sarasota County, land may stay covered with shallow, slow-moving floodwater for days or even weeks. In 2001, for example, the lower Myakka River in the Venice area rose to heights of about 18 feet and took 30 days to completely receed. The short notice, large depths, and high velocities of flash floods make these types of floods particularly dangerous. Riverine floodplains range from narrow, confined channels (as in steep river valleys in hilly and mountainous areas) to wide, flat areas (as in much of the Midwest and in many coastal areas). In the steep narrow valleys, flooding usually occurs quickly and is of short duration, but is likely to be rapid and deep. In relatively flat floodplains, areas may remain inundated for days or even weeks, but floodwaters are typically slow-moving and shallow.  Along major rivers with very large drainage basins, the timing and elevations of flood peaks can be predicted far in advance and with considerable accuracy. In very small basins, flooding may be more difficult to predict to provide useful warning time. Generally, the smaller the drainage basin, the more difficult it is to forecast the flood. For more local information about drainage basins see Watershed Management Planning.

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Shallow Flooding – Areas of known flooding that pond one to three feet depicted on a Flood Insurance Rate Map (FIRM) as AH Zone or a sheet flow depicted on a Flood Insurance Rate Map as AO and measurable flooding depths of one to three feet. Greater population density generally increases the amount of impervious area, e.g., pavement and buildings. This reduction in the amount of natural ground that can absorb rainfall results in an increase in the amount of surface runoff generated. Uncontrolled, this runoff may be channeled to areas that cause flooding of structures and roadways. This may be especially true where the predevelopment land surface had a gently sloping surface with no defined channels.  Such areas are subject to shallow sheet flooding during storms, but urbanization and other development speeds the accumulation of floodwater.

Stormwater Environmental Utility 

Sarasota County Stormwater Environmental Utility

Storm Surge  is the increase in water surface elevation above normal tide levels due primarily to low barometric pressure and the piling up of waters in coastal areas as a result of wind action over a long stretch of open water. The low pressure inside a storm or hurricane’s eye creates suction like a straw, creating a dome of water near the center of the storm. In the deep ocean, this dome of water sinks and harmlessly flows away. But as a storm nears land, strong winds in the storm push this dome of water toward the shore, the rising sea floor blocks the water’s escape and it comes a shore as deadly storm surge. An intense hurricane can send a dome of water many miles wide and more than 25 feet deep barreling toward the shore as the storm hits land. Depending upon local topography, a storm surge may inundate only a small area (such as along sections of the Northeast and Northwest coasts) or may inundate coastal lands for a mile or more inland from the shoreline (as in many areas of the south Atlantic and Gulf coasts). Storm surge is usually estimated by subtracting the regular/astrological tide level from the observed storm tide. Typical storm surge heights range from several feet to more than 25 feet. The exact height of the storm surge and which coastal areas will be flooded depends on many factors, including the strength, intensity and speed of the hurricane or storm; the direction it is moving relative to the shoreline; how rapidly the sea floor is sloping along the shore; the shape of the shoreline, and the astronomical tide. In general, storm surge is most damaging when it occurs along a shallow sloped shoreline, during high tide, in a highly populated and developed area with little or no natural buffers, such as barrier islands, coral reefs and coastal vegetation. Storm surge is also most damaging in the storm’s right front quadrant because the storm, its winds and ocean waves are all moving in an onshore direction due to the counter-clockwise rotation of hurricanes in the Northern Hemisphere. In contrast, to the left of the eye, ocean waves and sea-level rise are moving toward the shore, but the winds are blowing in an offshore direction, thru counteracting or moderating some of the effects of the storm surge. Storm surge causes sea levels to rise for a relatively short period of time (typically four to eight hours, though some areas may take much longer to recede to their pre-storm levels) – often resulting in extensive coastal flooding that can weaken or destroy coastal structures. By temporarily raising sea level, storm surge permits “dangerous and battering waves” and floating debris to access coastal areas and structures never conceived of nor built to withstand the punishing effects of ocean waves. It is these battering waves that cause most beach erosion and extensive damage to coastal structures such as buildings, roadways, bridges, marinas, piers, boardwalks, and sea walls.

In addition to storm surge, wave action is an important aspect of coastal storms. Breaking waves at the shoreline become very destructive, causing damages to natural and manmade structures by hydrodynamic pressure, battering solid objects and scouring sand from around foundations. Components of wave action include wave set-up and wave run-up. Wave set-up is the super elevation of the water surface over normal surge elevation and is caused by onshore mass transport of the water by wave action alone. Wave run-up is the action of a wave after it breaks and the water “runs up” the shoreline or other obstacle, flooding areas not reached by the storm surge itself. Where vertical obstructions such as seawalls are present, wave run-up is translated into upward movement of the water. As waves move toward the shore, they encounter several obstacles. The first obstacle is the sloping bottom near the shoreline. When waves reach a water depth equal to about 1.3 times the wave height, the wave breaks. Breaking waves dissipate their energy by generating turbulence in the water and by transporting sediment lifted off the bottom and tossed around by the turbulent water. As the turbulent water travels forward, it expends most of its remaining energy as it rushed up the beach slope. The beach adjusts to changes in wave energy by changing its profile. Beach material is moved either seaward, creating an offshore berm, or landward, building up the beach. The beach is constantly adjusting to both wave energy and water level. Offshore berms built up by the natural action of waves serve to protect the beach from most storm waves. When major storms generate larger waves, the berm may be eroded and berm material carried offshore. With the protective value of the berm removed, large waves can overtop the beach. In severe storms such as hurricanes 50- to 100-foot wide dunes may disappear in only a few hours. Although the dunes and beach may eventually recover to their previous conditions, the process may require many years. While hurricanes are the most violent type of storm and receive the most attention, serious flooding and erosion problems are also caused by other coastal storms. In the Atlantic, extratropical storms that develop in mid-latitudes in the fall, winter and spring occur much more frequently than tropical hurricanes, and may be more than 1,000 miles in diameter, much larger than a tropical hurricane. Although maximum winds are of lower velocity than tropical hurricane winds (75 miles/hr. or greater), some wind gusts of hurricane velocity may occur with extratropical storms. Extratropical storms that occur along the northern part of the east coast of the United States, accompanied by strong winds blowing from the northeast quadrant, are called northeasters. They may stall off the coast of the North Atlantic states and produce high tides that persist for several days.

Subsidence is a type of ground failure that can lower the ground surface, causing or increasing flood damage in areas of high ground water, tides, storm surges or over bank stream flow. Subsidence occurs in nearly all the states. Ground failure due to subsidence can result in increased flood damages for two main reasons. If the land surface is lowered it may be more frequently or more deeply flooded. In addition, subsidence can block or otherwise alter drainage patterns leading to deeper or unexpected flooding.  Subsidence is the result of both natural processes and human activities. Natural causes include solution (karts topography), consolidation of subsurface materials (such as wetlands soils), and movements in the earth’s crust. Human activities, which accelerate the natural processes leading to subsidence, include mining, inadequate compaction of fill material during construction, and withdrawal of oil or water from subsurface deposits. Baytown, Texas, near Houston, is a classic example of a local flood problems greatly aggravated by subsidence resulting from the latter situation.

Surface Water Runoff - When rainfall reaches the Earth’s surface, water evaporates, infiltrates into the soil, or runs over the surface. The kinds of ground cover greatly influence the proportions of each of these actions. In various types of communities, and within communities, there are different cover types. For example, an urban area, like a city, might have these cover types:

• Open space (lawns, golf courses, parks) generally covered with grass

• Streets and roads

• Paved parking lots, shopping centers

• Houses and residential areas

• Offices and business areas