SECTION 3: HAZARD IDENTIFICATION AND ANALYSIS

This section provides a description of the known flood hazards in Savannah according to best available data. It includes information on the source, frequency, extent and magnitude of various types of known flood hazards as well as a discussion of historically recorded flood events. It also includes the current statistics for insured at-risk properties as made available through the National Flood Insurance Program, as well as for those properties that have filed repetitive flood claims. It concludes with a general discussion on the probability of future flood hazard occurrences for Savannah.

Scope of Study Area The flood risk assessment was completed for those areas in Chatham County that are within the incorporated City limits of Savannah. Figure 3.1 provides a base map that illustrates the boundaries of the study area in addition to major transportation routes and aerial photography.

The City of Savannah is located within portions of two major river basins: the Ogeechee River Basin and the Savannah River Basin. There is an expansive series of manmade canals and tributaries that help drain the City to the rivers, marshes, sounds and ultimately to the Atlantic Ocean. Figure 3.2 illustrates the various drainage basins for Chatham County. While all of Savannah’s incorporated areas were included in the flood risk assessment (including those recently annexed by the City), the core study area for this plan includes fourteen (14) drainage basins as listed below. Most of Savannah’s reported flood hazard problems are located within these basins, all of which are contiguous to Savannah’s most populated and developed areas.

 Bilbo Basin  Casey North  Casey South  Chippewa  Coffee Bluff  Dundee Canal  Fell Street  Harmon Canal  Horseshoe  Placentia  Springfield North  Springfield South  Wilshire  Windsor

Description of Study Area The City of Savannah has a total land area of approximately 97 square miles located in southeastern Georgia, nestled in close proximity to the Savannah River and the Atlantic Ocean. In 2007 the City had an estimated total population of 130,331, with another 118,138 residents living in other areas of Chatham County. The City also hosts millions of visitors every year, with tourism being an active and rapidly growing segment of the economy. The City's attractiveness as a visitor destination is enhanced by its internationally renowned historic district, abundant accommodations and easy accessibility. It is served by several primary highways including Interstates 95 and 16, as well as the Savannah / Hilton Head International Airport. SECTION 3: HAZARD IDENTIFICATION AND ANALYSIS

Figure 3.1: Base Map

Source: Savannah Area Geographic Information System

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Figure 3.2: Chatham County Drainage Basins

Source: Savannah Area Geographic Information System

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The climate in southeastern Georgia is warm and temperate to subtropical. The average temperature in January is 63 degrees Fahrenheit (°F), and is 92°F in July, and the average annual precipitation is approximately 50 inches, with most precipitation occurring in August. While the Atlantic hurricane season lasts from June through November, most of the historic storms that have impacted Savannah occurred during the months of August and September.

The City is situated on a low coastal plain with much of its surrounding area consisting of tidal marshes. Elevations range from sea level along the coast to approximately 40 feet in downtown Savannah. The Savannah River (north of City) and the Ogeechee River (south of City) have drainage areas extending far beyond the limits of Savannah and Chatham County. Other streams and creeks have chiefly tidal estuaries within the area and include the Little Ogeechee River, Vernon River, Bear River, Wilmington River, Bull River, and numerous tributaries to these. Main openings to the Atlantic Ocean are Ossabaw Sound and Wassaw Sound, both of which are wide and deep.

Description of Known Flood Hazards

Flooding is the most frequent and costly natural hazard in the United States, a hazard that has caused more than 10,000 deaths since 1900. Nearly 90 percent of presidential disaster declarations result from natural events where flooding was a major component – including the two historical presidential disaster declarations for the City of Savannah and Chatham County, Georgia (1994 and 1998).

As disastrous as it can be, flooding is part of the earth’s natural hydrologic cycle. This cycle constantly circulates water throughout the environment and helps maintain an overall balance between water in the air, on the surface and in the ground. Sometimes however this system has temporary imbalances that send more water to an area than it can normally handle. This situation results in flooding.

Throughout its long history, the City of Savannah has always been prone to flood hazards. Historical data show that structural flooding has been a regular and costly occurrence in Savannah for more than a century. In addition, the City has seen the frequent flooding of streets and intersections which in turn impedes traffic flow and causes significant interruptions to mobility and commerce. Either way, when flooding does occur in Savannah, the community experiences significant social, economic and environmental impacts that are deemed unacceptable to the City.

The cause of flooding in Savannah can be attributed to a number of factors, including its low elevation, relatively flat terrain, close proximity to the coast, 6 to 9 foot tides, and an abundance of rivers, creeks and streams that surround and traverse the City. Another contributing factor is the large amount of developed and impervious land throughout the City which limits ground absorption and increases surface water runoff. Early in its history, the City constructed a series of canals to convey stormwater. Without these canals, development in many parts of the City would not have been possible, and over the years, these canals have been supplemented by additional drainage improvements of varying capacities to help alleviate potential flooding.

As a result, flood hazard mitigation has long remained a top priority for the City of Savannah as is evident by numerous engineering studies, task force reports and drainage improvements throughout the last 20 years. This includes the preparation of the 1987 Drainage Improvement Task Force Report and the 1994 Flood Mitigation Capital Improvements Plan. While many

City of Savannah Flood Hazard Mitigation Plan 3-4 SECTION 3: HAZARD IDENTIFICATION AND ANALYSIS recurring flood problems have been solved, there remains a variety of known flood hazards for the City to continue addressing in its sustained mitigation planning efforts.

Sources and Types of Flooding In Savannah, flood hazards are generally the result of excessive precipitation, but for planning purposes they have been classified under three unique categories: (1) riverine flood; (2) flash flood; and (3) coastal flood. Each of these different types of flood hazards is further described below.

Riverine Flood Riverine flood hazards are characterized by the slow rise of water levels as the result of heavy precipitation over a given watershed for a long period of time. When the actual amount of river or stream flow is larger than the amount that the channel or basin can hold, the water will overflow its banks and flood the adjacent low-lying areas called floodplains. Riverine floods typically develop slowly and may last for several days or even weeks.

Riverine floods are described in terms of their extent (including the horizontal area affected and the vertical depth of floodwater) and the related probability of occurrence. Flood studies use detailed hydrological and hydraulic analyses to determine the extent and historical records to determine the probability of occurrence for different extents of flooding. The probability of occurrence is expressed as the percentage chance that a flood of a specific extent will occur in any given year. The severity of riverine flooding is typically determined by a combination of several major factors, including: duration and intensity of precipitation; stream and river basin topography and physiography; recent soil moisture conditions; the degree of vegetative clearing and impervious surface; and the capacity of existing stormwater control facilities.

The City of Savannah lies immediately along the banks of the tidally-influenced Savannah River in addition to Wassaw and Ossabaw sounds, with numerous tributaries and manmade canals running throughout its jurisdiction that are very susceptible to overflowing their banks during and following excessive precipitation and coastal storm events. While flash flooding caused by surface water runoff is certainly more common in Savannah, the less frequent but large-scale riverine flood event (such as the “100-year flood”) will cause significantly more damage and economic disruption for the area. Savannah’s floodplains, the areas at most risk to such events, have been studied and mapped by the Federal Emergency Management Agency (FEMA) as special flood hazard areas.

Flash Flood Flash floods, as the name suggests, occur suddenly after a brief but intense and concentrated downpour. The most destructive and dangerous of flash floods occur in areas with steep slopes and narrow stream valleys. However, flash flooding caused by surface water runoff can also have a significant impact on people and properties in localized areas. If drainage conditions are inadequate to accommodate rainfall through a combination of infiltration into the ground and surface runoff, accumulation of water in certain areas may cause flood hazards that range from nuisance ponding in streets to damaging structural flooding.

Flash flood hazards caused by surface water runoff are most common in urbanized cities, where greater population density generally increases the amount of impervious surface (e.g., pavement and buildings). This reduction in natural groundcover that can absorb and retain rainfall results in an increase in the amount of surface water runoff generated. Unless drainage systems are maintained and expanded to keep pace with increases in surface water runoff, flood hazards will become more severe as areas become more developed. Even when systems

City of Savannah Flood Hazard Mitigation Plan 3-5 SECTION 3: HAZARD IDENTIFICATION AND ANALYSIS are constructed to adequately meet drainage standards, flooding can occur when the conveyance of stormwater through these systems is obstructed by debris, sediment and other materials that limit the volume of drainage.

Most flash flood events are caused by slow-moving thunderstorms in a localized area or by continuous heavy rainfall associated with hurricanes and tropical storms. They often move fast, terminate quickly, and can occur in areas generally not considered at risk to flooding (including areas outside of FEMA-identified special flood hazard areas). Although the duration of these events is usually brief, the damages and interruptions they cause can be quite severe. Unlike riverine floods, flash floods cannot be predicted accurately and can develop rapidly with little to no warning. The lack of warning often results in increased damage to property that could have been prevented with more advance notice, and particularly for vehicles left unattended in areas susceptible to flash flooding.

The City of Savannah experiences frequent flash flood events associated with surface water runoff that exceeds and overwhelms the capacity of local drainage systems. These floods are most often caused by isolated, high-intensity storm events of relatively short duration (1 to 3 hours) that concentrate heavy rains over the City’s urbanized areas, and the flooding is significantly more severe in Savannah when occurring at times of high tide. Even brief periods of torrential rain are known to cause considerable flooding of streets and intersections in localized areas throughout the City. This recurrent flood problem for Savannah is generally confined to limited areas of low elevation adjacent or in proximity to streams and canals, as well as low elevation depressions with little or no drainage outlet. It is made worse in areas that still rely on outdated drainage systems or where such systems routinely experience obstructions and blockages caused by debris.

Coastal Flood / Storm Surge Coastal flood hazards result from the effects of wind-driven waves and storm surge produced by hurricanes, tropical storms and other large coastal storms. While the City of Savannah is not located along an immediate shoreline that experiences regular wave action, it is located in an area that is extremely vulnerable to episodic tidal flooding and storm surge inundation (e.g., the Savannah River).

Storm surge occurs when the water level of a tidally influenced body of water increases above the normal astronomical high tide, and are most common in conjunction with coastal storms with massive low-pressure systems with cyclonic flows such as hurricanes, tropical storms and nor’easters. Storm-driven winds combined with low barometric pressure cause the water surface to rise. Where astronomic tide ranges are pronounced, the total height of water and extent of land inundated would, in part, depend on whether the peak surge arrived at the lower or higher limits of the astronomical tide. Storms landfalling during peak high tides have surge heights and more extensive flood inundation limits. Storm surges will inundate coastal floodplains by dune overwash, tidal elevation rise in inland bays and harbors, and backwater flooding through coastal river mouths. The duration of a storm is the most influential factor affecting the severity and impact of storm surges. While hurricanes and tropical storms often move through areas relatively quickly, nor’easters can last for days and multiple tidal cycles – often causing major coastal flooding, erosion and damage.

A storm surge is often described as a wave that has outrun its generating source and become a long period swell. It is often recognized as a large dome of water that may be 50 to 100 miles wide and rising anywhere from four to five feet in a Category 1 hurricane up to 30 feet in a Category 5 storm. The storm surge arrives ahead of the storm center’s actual landfall and the

City of Savannah Flood Hazard Mitigation Plan 3-6 SECTION 3: HAZARD IDENTIFICATION AND ANALYSIS more intense the storm is, the sooner the surge arrives. Water rise can be very rapid, posing a serious threat to those who have not yet evacuated flood-prone areas. The surge is always highest in the right-front quadrant of the direction in which the storm is moving. As the storm approaches shore, the greatest storm surge will be to the north of the low-pressure system or hurricane eye. Such a surge of high water topped by waves driven by hurricane force winds can be devastating to coastal regions, causing severe beach erosion and property damage along the immediate shoreline and inland waterways.

The primary factors contributing to coastal flooding in Savannah are its location in a hurricane prone area, its openness to Atlantic Ocean storm surges and unfavorable, shallow bathymetry extending far offshore. Many of the large streams and sounds near the coast have wide mouths and are bordered by extensive areas of low marsh. In addition, the terrain at the coast is generally too low to provide an effective barrier. The offshore ocean depths are shallow for great distances, capable of generating extremely high storm surges with potential devastating impact in Savannah, particularly if driven at times of high tide.

Extent of Known Flood Hazards in Savannah

The periodic flooding of lands adjacent to rivers, streams and shorelines (land known as floodplain) is a natural and inevitable occurrence that can be expected to take place based upon established recurrence intervals. The recurrence interval of a flood is defined as the average time interval, in years, expected between a flood event of a particular magnitude and an equal or larger flood. Flood magnitude increases with increasing recurrence intervals, and floodplains are designated by the frequency of the flood that is large enough to cover them. For example, the 10-year floodplain will be inundated by the 10-year flood and the 100-year floodplain by the 100-year flood. Another way of expressing the flood frequency is the chance of occurrence in a given year, which is the percentage of the probability of flooding each year. For instance, the 100-year flood (also known as the “base flood”) has a one percent chance of occurring in any given year. The 500-year flood has a 0.2 percent chance of occurring in any given year.

Many areas of Savannah are susceptible to riverine, flash and coastal flood hazards. It is estimated that nearly 50 percent of the City’s incorporated areas are located in special flood hazard areas as determined by FEMA for flood insurance purposes. Figure 3.3 illustrates the location of the 1 percent and 0.2 percent annual chance special flood hazard areas as identified in the latest FEMA Flood Insurance Study for the City of Savannah (Effective September 26, 2008). Base flood elevations range from 11 to 20 feet, North American Vertical Datum 1988 (NAVD88). It also illustrates the coastal (VE) special flood hazard area, defined as the base flood with wave action. For more detailed illustrations of these special flood hazard areas, please see Appendix J for the series of basin-specific maps for each of the 14 drainage basins in the core study area.

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Figure 3.3: Special Flood Hazard Areas in Savannah

Source: Savannah Area Geographic Information System; Federal Emergency Management Agency

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While FEMA’s digital flood insurance data is often recognized as best available data for floodplain management planning purposes, it does not always take into account or reflect the most accurate and up-to-date risk for flood hazards – particularly for the more frequent, less severe flash flood hazards caused by surface water runoff. FEMA flood hazard maps do not typically account for flood problems caused by small depressions or low points in the terrain where stormwater collects – a situation that is often exacerbated by increases in impervious surfaces. Significant flooding and flood-related losses often do occur outside of delineated special flood hazard areas. In fact, according to FEMA, approximately 20 to 25 percent of all flood claims occur outside of mapped flood hazard areas.

Figure 3.4 illustrates the general location of areas with recorded flash flooding as reported by residents through the City of Savannah’s Customer Service Call Center or by staff from the City’s Stormwater Management Department. As can be seen, many of the reported flooding occurrences are located outside of identified special flood hazard areas. These reported instances of flooding include flooded properties and standing water in proximity to buildings, but do not necessarily include confirmed structural flood damages.

Figure 3.5 illustrates the locations of historically reported flooded intersections throughout Savannah as recorded by the City’s Stormwater Management Department. However, it should be noted that this database does not include all locations of known flood problems. During heavy rain, the City recommends that the following streets be avoided:  Fairmont-Hanover-Hodgson  Victory and Ogeechee  Goebel Ave. at President  President St. from Gen. McIntosh to Pennsylvania Ave.  Gwinnett and Skidaway  Gwinnett at City Lot  Whitaker and 33rd  Abercorn from DeRenne to Victory  Habersham from DeRenne to Victory  Paulsen from DeRenne to Victory  Reynolds from DeRenne to Victory  Harmon from DeRenne to Victory  Bay Street, East of Fell/Brittany  Fell/Baker/Jenks from Bay Street to Augusta Avenue  Henry from Cedar Street to Waters Avenue

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Figure 3.4: General Areas of Historically Reported Flash Flooding

Source: Savannah Area Geographic Information System; Savannah Stormwater Management Department

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Figure 3.5: Historically Reported Flooded Intersections in Savannah

Source: Savannah Area Geographic Information System; Savannah Stormwater Management Department

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The extent of potential coastal storm surge flooding is quite different from those special flood hazard areas identified through flood insurance studies. In order to identify those areas susceptible to potential storm surge inundation, the City of Savannah and Chatham County utilize Sea, Lake, and Overland Surge from Hurricanes (SLOSH) data from a 2002 Georgia hurricane study conducted by FEMA in cooperation with the United States Army Corps of Engineers and the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA). SLOSH is a numerical storm surge model developed between 1967 and 1992 by C.J. Jelesnianski, A.D. Taylor, J. Chin, and W.A. Shaffer of NOAA to estimate storm surge depths resulting from historical, hypothetical, or predicted hurricanes. SLOSH takes into account a storm's pressure, size, forward speed, forecast track, wind speeds, and topographical data for the impacted area. Figure 3.6 illustrates the storm surge inundation zones for various categories of hurricanes for Chatham County as identified through data derived from SLOSH.

It is important to note that the exact time, location and direction of a hurricane's landfall are crucial factors in determining which areas will be inundated by the storm surge, and to what depth. The SLOSH model calculations for Chatham County included an initial water surface elevation of +5.0 feet consisting of a tidal anomaly of +3.0 feet to simulate conditions at high tide and an additional 2.0 feet, based on tidal gauge observations. Therefore, the SLOSH model is best used for defining areas inundated by the potential maximum storm surge. The highest storm surges recorded in the Savannah area occurred during the hurricanes of 1881 and 1893, which reportedly caused storm surge heights up to 15 and 18 feet, respectively, as measured at Savannah Beach (Tybee Island).

It should also be noted that anticipated sea level rise along the Georgia coast will increase the risk of damage and losses due to future coastal flooding and storm surge events. Rising sea level over time will shorten the return period (increasing the frequency) of significant flood events. For example, sea level rise of 1 foot over a typical project analysis period (50 years) may cause a flood event currently of annual probability 2 percent (50-year flood) to become an event of 10 percent annual probability (10-year flood). This increased probability will have an exacerbating effect on the extent of flood zones, exposure to flood hazards and the estimation of potential damages and losses, but one that is typically only analyzed during detailed feasibility studies for projects proposed by the U.S. Army Corps of Engineers. No detailed studies on projected sea level rise and its implications for existing flood hazards in Savannah have been performed at this time, but such studies will be taken into account during future updates to this plan.

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Figure 3.6: Chatham County Storm Surge Inundation Zones

Source: Savannah Area Geographic Information System; Chatham County Emergency Management Agency

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History of Flood Hazard Events

The City of Savannah has experienced numerous flood events of varying severity in its past. This section provides information on some of the more notable historic flood occurrences in the area as recorded by a number of sources, as well as some of the City’s more recent flood hazard events. This section also provides data on historical flood insurance claim data as made available by FEMA under the National Flood Insurance Program.

Notable Historic Flood Occurrences Many of the most significant flood hazard occurrences in Savannah’s long history are attributed to major coastal storms such as hurricanes and tropical storms. These events have thepotential to cause devastating inland and coastal flood events for the area, particularly when combined with high tides. According to local historical information and the most recent Flood Insurance Study for Chatham County (2008), major storms and hurricanes have caused flooding in the area in 1871, 1881, 1885, 1893, 1896, 1898, 1911, 1940, 1944, 1947, 1952, 1959, 1979, 1989, 1994, 1996 and 2005. Figure 3.7 shows the historic storm tracks of all hurricanes and tropical storms that have come within 100 miles of Chatham County since 1851. The figure does not include the tracks of other low pressure systems such as tropical depressions or extratropical storms, though it is worth noting that these systems often do retain characteristics that will cause significant flood hazards as well.

A brief history of major storms that have affected the Savannah area and its vicinity during the past 140 years is summarized below. All loss figures include total reported damages sustained by both wind and flood hazards, and have been adjusted for inflation to 2008 dollars.

August 27, 1881 A major hurricane made landfall south of Savannah and caused an estimated $34.7 million in damages. It is estimated that 335 people were killed in and near the City, and nearly 100 vessels were destroyed along the Atlantic coast. Damage was very heavy on Tybee Island and other coastal areas near Savannah. The highest tide observed was estimated to reach an elevation of 15.6 feet at Savannah Beach, approximating a flood of at least 1 percent annual chance magnitude.

August 27, 1893 This major hurricane was accompanied by a tremendous storm surge that submerged the islands along the Georgia and South Carolina coasts. Between 2,000 and 2,500 people lost their lives on the coastal islands and in the lowland between Tybee Island and Charleston. Property damage along the Atlantic coast was estimated at $231 million. Nearly every building on Tybee Island was damaged and the railroad to the island was wrecked. The highest tide known to have occurred in Chatham County was estimated to have a range of 16.1 to 18.6 feet at Savannah Beach.

September 28, 1896 This hurricane entered the northwestern Florida coast and passed through southeastern Georgia and South Carolina. Hurricane winds persisted when the hurricane moved inland, with maximum winds of 75 miles per hour in Savannah. Total damage in Savannah was estimated at $28 million. Damage was also heavy on Tybee Island but since the storm occurred during a low tide period, destruction caused by storm surge was relatively light compared with the hurricanes of 1881 and 1893.

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Figure 3.7: Historic Storm Tracks within 100 miles of Chatham County, 1851–2007

Source: National Oceanic and Atmospheric Administration

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August 30, 1898 This hurricane passed over Tybee Island with wind speeds estimated at 100 miles per hour. The storm surge was not high enough to cause extensive damage; however, the hurricane was accompanied by very heavy rain, and the countryside was flooded for 100 miles around Savannah. Most roads and railroads were impassable because of high water.

August 28, 1911 The center of this hurricane entered the coast between Savannah and Charleston, with a maximum wind of 88 miles per hour recorded in Savannah. Damage in the Savannah area was remarkably low; however, property on Tybee Island was heavily damaged. Excessive rains accompanied the storm and caused considerable damage to roads, crops, and other property throughout the area.

August 11, 1940 This was the first hurricane to affect Georgia since August 1911, and made landfall along the South Carolina coast to the north of Savannah. The winds in Savannah reportedly reached 73 miles per hour (through some reports indicate winds of at least 105 miles per hour were experienced). Damage in the Savannah area was estimated at $13.3 million. The highest tide observed at Beaufort, South Carolina, was estimated to be 11.5 feet. High tides of 6.5 and 5.5 feet were recorded at Fort Pulaski, Georgia, and at Fort Jackson, Savannah Harbor, Georgia, respectively.

October 12 - 23, 1944 This hurricane entered the gulf coast of Florida and moved northeastward across the peninsula. Its center crossed the east coast near Jacksonville, Florida, in a north- northeast direction and moved inland again near Savannah. The hurricane was downgraded to a tropical storm by the time it reached Georgia. The highest tide, 5.0 feet along the Georgia coast, was observed at Fort Pulaski, near the mouth of the Savannah River. The estimated damage in Georgia was $6.2 million.

October 15, 1947 The center of this hurricane entered the Georgia coast just south of Savannah, where the maximum wind speed was 77 miles per hour. Heavy losses were sustained in Savannah and Savannah Beach, where more than 1,500 buildings were substantially damaged. Total damage in the coastal area was estimated at more than $19.5 million. The highest tide, 7.0 feet, was recorded at Fort Jackson, Savannah Harbor.

August 30, 1952 (Hurricane Able) Hurricane Able made landfall near Beaufort, South Carolina with maximum winds of approximately 100 miles per hour. Total damage from this storm was estimated at about $23 million.

September 29, 1959 (Hurricane Gracie) Hurricane Gracie made landfall along the South Carolina coast near Beaufort. Wind gusts of hurricane force were felt in the Savannah area, and damage was inflicted over the upper Georgia coastal area. The total damage inflicted by the storm was estimated at $105 million with damage in Georgia estimated at more than $3.8 million. High water marks, which were reported near Edisto Beach, South Carolina, ranged from 6.4 to 11.0 feet.

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September 4, 1979 (Hurricane David) Hurricane David was the most intense storm of the century to affect the islands of the eastern Caribbean. However, the storm was not a major hurricane when it struck the United States. David struck just north of Palm Beach, Florida, on September 3 and made a second landfall about 24 hours later near Savannah Beach with winds of 92 miles per hour. In the United States, David was responsible for five deaths and about $901 million in damages.

September 9 - September 25, 1989 (Hurricane Hugo) Hurricane Hugo was a destructive Category 5 hurricane that killed 82 people, left 56,000 homeless and caused $16.3 billion in damages, making it the most destructive hurricane ever recorded up to that time. Hugo was originally forecast to move toward Savannah, but instead turned north toward Charleston, South Carolina. Savannah was evacuated in anticipation of Hugo but saw no effects other than isolated showers.

September 7 - September 19, 1999 (Hurricane Floyd) While it fortunately spared any damage the Savannah area, Hurricane Floyd triggered the second largest evacuation in U.S. history when 2.6 million coastal residents of five states including around 350,000 people in Georgia, were ordered from their homes as Hurricane Floyd approached. Floyd struck the Bahamas at peak strength, causing heavy damage. It then paralleled the east coast of the U.S., causing massive evacuations and costly preparations. In total, Floyd was responsible for 57 fatalities and $7.4 billion in damage, mostly as the result of riverine flooding in North Carolina.

Recent Flood Events in Savannah The threat of flooding in Savannah certainly goes beyond the threat of hurricanes and other major coastal storms. In more recent years, the most significant and frequent flood hazard problems for the area can be attributed to smaller weather systems that cause torrential downpours in a short period of time that in turn cause surface water runoff flooding for low-lying areas. Often, as described earlier in this section, these areas are located outside of those special flood hazard areas identified by FEMA for the 1 percent annual chance flood.

In July 1982, the City of Savannah experienced two major flooding events that left hundreds of homes flooded in the Fell Street and Casey North basins. Following these events, the City adopted a basin-wide approach to implementing drainage improvements that continues today. Further, as a result of a Drainage Task Force Report in 1985, the City adopted an aggressive goal that no structure would be inundated due to a storm event of a 10 percent annual chance or less frequency of occurrence (this is equivalent to 7 inches of rainfall within a 24-hour period). While numerous drainage projects have since and continue to be implemented, the City of Savannah continues to experience frequent flooding occurrences of varying magnitudes. Much of this can be attributed to the flat topography which limits the ability of existing stormwater systems to drain floodwaters from rapid, heavy rainfall events. The most recurrent problems for Savannah in recent years are minor flash floods caused by surface water runoff in locations of low elevation with inadequate drainage, and particularly where storm drains are blocked by debris.

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Photos of Recent Flood Events in Savannah

Street flooding is a frequent occurrence in the Flooding in Savannah often times requires the Ardsley Park area. (Photo courtesy of the City of City to evacuate residents of flood prone areas. Savannah) (Photo courtesy of the City of Savannah)

The flooding of vehicles parked in low lying areas The City’s top priority for drainage improvement is a significant problem in many areas throughout projects is the elimination of flooding to homes Savannah. This photo was taken standing on and businesses, particularly those that have Washington Avenue looking east to Paulsen flooded repetitively over the years. (Photo Street. (Photo courtesy of the City of Savannah) courtesy of the City of Savannah)

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According to data made available through the National Weather Service’s National Climatic Data Center (NCDC), twenty major flood events were reported for the City of Savannah between January 1994 and December 2007. Many of these events are also confirmed through the database of reported flash flooding per the City’s Customer Service Call Center. These events resulted in no fatalities, two injuries and an estimated $23.3 million in property damage (adjusted for inflation to 2008 dollars).

Table 3.1 summarizes the information as recorded by NCDC for each historical event. This data does not include inland or coastal flood events as reported for areas outside the incorporated City limits of Savannah. All property damage figures should be considered general estimates, and have been adjusted for inflation to 2008 dollars.

Table 3.1: Recent Flood Hazard Events in Savannah, 1994–2007 Fatalities / Property Date Flood Type Description Injuries Damage Heavy rain of 3 to 4.25 inches caused street flooding in a poorly drained and low-lying area along Baker Street in 9/2/1994 Flash Flood 0 / 0 $73,500 Savannah. Evacuation of the area began around 9:00 PM as flood waters produced chest-high water in some locations. Flood waters receded by midday on the third. The Baker Street area of Savannah had to be evacuated after water inundated several residences. Little or no damage was 10/2/1994 Flash Flood 0 / 0 $147,000 reported elsewhere in the City or County. The Baker Street area remained closed due to flooding from the remnants of Tropical Depression Ten through the third of October. Low-lying intersections and neighborhoods experienced flash Riverine Flood floods when 7-14 inches of rain fell between midnight on the twelfth and 5:00 AM on the thirteenth. Road closings began * Resulting around 12:55 AM and more than 110 roads were closed from cumulative across Chatham County. The Baker Street area in Savannah 10/12/1994 effect of weeks 0 / 0 $7,352,000 began evacuating residents early in the afternoon. Heavy of heavy rains rains flooded the transmitter site of station WIZA-AM 1450 on attributed to the Gwinnet Street in Savannah and interrupted radio effects of El transmissions at 3:00 PM EST. In Bloomingdale, more than Nino eighty people were evacuated throughout the afternoon as water quickly flooded their homes. Street flooding was reported in areas with poor drainage; 6/29/1995 Flash Flood 0 / 0 $35,000 several businesses had some minor flood damage as water got into some first floor levels. The remnants of Tropical Storm Jerry produced 10 to 14 inches of rain across the southeastern counties of Georgia from August 24 through August 27. Water in residences Riverine Flood / forced 72 residents to evacuate. Eighteen homes had minor 8/26/1995 Flash Flood / 0 / 0 $5,003,000 damage and five homes sustained major damage. Eighty Coastal Flood roads, streets, and intersections were closed with varying degrees of damage. The heavy rain produced flash flooding, coastal flooding at times of high tide, and river flooding afterwards. Eight to ten (8-10) inches of rain fell in 3-4 hours in and around Savannah. As a result, 50 streets and 100 homes were flooded to various degrees. Numerous businesses had water several inches deep. There were 31,000 residents without power for several hours. This event also occurred 7/5/1996 Flash Flood 0 / 2 $1,388,000 close to high tide. Some streets had water up to headlights on cars while some homes had water almost knee deep. Several car dealerships had significant damage to some cars. Two elderly men barely escaped with their lives when their car stalled. By the time they were rescued, water was within six inches of filling the inside of the car.

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Table 3.1: Recent Flood Hazard Events in Savannah, 1994–2007 Fatalities / Property Date Flood Type Description Injuries Damage Four to eight (4-8) inches of rain fell in 2 to 4 hours, causing 8/7/1996 Flash Flood 0 / 0 $104,000 flash flooding and flooding of streets and small streams. Four to seven (4-7) inches of rain within 24 hours caused 1/23/1998 Flash Flood 0 / 0 $0 flooding of roads and roads to be closed for several hours. Slow moving showers and thunderstorms developed repeatedly across Chatham County and Effingham County during the day. Twenty-four hour rainfall amounts ranged from about seven inches to over 13 inches. As a result of the flooding, over 500 homes and businesses were damaged to 6/29/1999 Riverine Flood 0 / 0 $9,133,500 varying degrees and almost 600 automobiles were damaged. Water was as much as six feet deep in some places. Numerous roads were washed out and/or closed during the flooding. Estimated dollar damage for public property was 4.5 million dollars and at least another 2.5 million dollars for private property. Tropical Storm Kyle dumped 3 to 5 inches of rain in the Savannah area within a 12 hour period. This very heavy 10/11/2002 Flash Flood 0 / 0 $0 rainfall caused flooding of roads, low lying areas and places with poor drainage. Numerous cars stalled and roads were closed as the flooding began to endanger lives. Significant flooding occurred in several neighborhoods, making some roads impassable. WSAV meteorologist reported 37th Street completely flooded and impassable. 4/7/2003 Flash Flood 0 / 0 $0 WTOC meteorologist reported that there were numerous roads that were impassable due to high water. Additionally, motorists were getting stranded in some areas according to the Chatham County Emergency Management. Thunderstorms dumped an estimated 4 to 6 inches of rain around high tide causing flooding in downtown Savannah. 7/24/2003 Flash Flood 0 / 0 $0 Numerous streets and underpasses were closed due to flooding. Four people were rescued from their cars after driving into water that caused cars to stall. Thunderstorm wind damage and flash flooding occurred in southeast Georgia due to the remnants of Tropical Storm Bonnie. Radar estimated around 4 inches of rain fell across 8/12/2004 Flash Flood 0 / 0 $0 parts of Chatham County in approximately one hour. Flooding was reported in the Windsor Forest area and high water approached some homes. Heavy rainfall associated with Tropical Storm Tammy flooded 10/5/2005 Flash Flood 0 / 0 $0 General McIntosh Boulevard, Louisville Road, and Lathrop Avenue. Water was reported in houses at Halcyon Bluff. Vehicles 7/6/2006 Flash Flood 0 / 0 $10,500 stalled on Old Commercial Drive. A weak frontal boundary in combination with sea breeze and numerous low level boundaries in a highly unstable environment resulted in numerous showers and 7/30/2007 Flash Flood 0 / 0 $8,000 thunderstorms across the region. Numerous road closures were reported in Downtown Savannah. High water was reported entering some apartments, and cars were reported floating down the roadway at 65th and Abercorn Street. The presence of an area of surface low pressure southwest of the area, an approaching frontal boundary from the northwest, and abundant weak upper level disturbances in a deep tropically moist environment, resulted in heavy rainfall and flash flooding across the area. The public reported 1.5 feet of 9/1/2007 Flash Flood 0 / 0 $0 standing water at an underpass. Additionally, a major road in town was closed due to high water, and it was reported to be impassable by vehicles. High water was reported on Delano Street, Winburn Street, Hastings Street, Cornwall Street, and at the intersection of Gwinnett and Stiles Streets.

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Table 3.1: Recent Flood Hazard Events in Savannah, 1994–2007 Fatalities / Property Date Flood Type Description Injuries Damage 9/13/2007 Flash Flood 0 / 0 $0 No description provided. A trough of low pressure in a moisture rich environment resulted in numerous showers and thunderstorms across southeast Georgia. Numerous streets were reported impassable in Savannah. A few streets that were reported to be impassable included, Paulsen Street and 63rd Street, 9/21/2007 Flash Flood 0 / 0 $0 Paulsen Street and 61st Street, East Victory and Live Oak, Victory and Abercorn around Ardsley Park, the 500 block of Pennsylvania Avenue, Derenne Avenue, Bull Street, 62nd Street and Spring Hill, and Pine Street. The parking area at the Memorial Medical Center was reported to be under one foot of water. Low pressure developed off the coast of South Carolina and Georgia as a potent upper level disturbance moved across the region. The pressure gradient between the area of low pressure and a wedge of high pressure associated with strong cold air damming, produced strong winds along the coast. Moderate to heavy rains also fell across the area, 12/21/2007 Flash Flood 0 / 0 $5,000 bringing much needed rainfall to some drought stricken areas. Chatham County Emergency Management reported that several roads were closed due to flash flooding throughout the area, including in the City of Savannah. One house was evacuated due to flooding on East 33rd street. The intersection of Robert Miller and Highway 301 was reported to be flooded under the railroad crossing. Approximately 3.8 inches of rain fell within one hour causing flooding in the Habersham Village and Ardsley Park areas of Savannah. The severe localized rains had reportedly overwhelmed existing drainage systems and sent water 7/5/2008 Flash Flood 0 / 0 Unknown gushing out of storm drains. The City had no reports of building damage but multiple vehicles were flooded. There were also reports of some commercial properties being flooded by the wake of passing cars on flooded streets. Total 0 / 2 $23,259,500 Source: National Climatic Data Center, 2008, with the exception of the 7/5/2008 event for which information was provided by the Savannah Morning News (Mary Landers - Sunday, July 13, 2008).

Historical Summary of Insured Flood Losses The City of Savannah has participated in the National Flood Insurance Program (NFIP) since 1971, immediately following the production of initial flood hazard boundary maps that made the purchase of federally-backed flood insurance available to its property owners. Since 1992, the City has also actively participated in the NFIP’s Community Rating System. The CRS, created in 1990, rewards NFIP policy holders with premium rate reductions based on community floodplain management activities designed to reduce flood losses that go beyond minimum NFIP requirements. As of April 30, 2008, there were 8,004 NFIP policies in force in the City of Savannah providing over $1.7 billion in flood insurance coverage. The total amount of written premiums in-force for Savannah total nearly $3.5 million annually.

According to FEMA flood insurance policy records (as of April 30th, 2008), there have been more than 1,898 flood losses reported in the City of Savannah through the NFIP since 1971, totaling more than $26 million in claims payments (average claim payment of $13,786). These losses include both inland (freshwater) and coastal flooding events. It should be emphasized that these numbers include only those losses to structures that were insured through the NFIP policies, and for losses in which claims were sought and received. It is understood that many additional instances of flood losses occurred in Savannah that were either uninsured, denied

City of Savannah Flood Hazard Mitigation Plan 3-21 SECTION 3: HAZARD IDENTIFICATION AND ANALYSIS claims payment, or not reported.

Repetitive Loss Properties FEMA defines a repetitive loss property as any insurable building for which two or more claims of more than $1,000 were paid by the NFIP within any rolling 10-year period, since 1978. A repetitive loss property may or may not be currently insured by the NFIP. Currently there are more than 122,000 repetitive loss properties nationwide.

According to FEMA repetitive loss property records (as of April 30th, 2008), there are 223 “non- mitigated” repetitive loss properties located in the City of Savannah. These properties have accounted for a total of 544 losses and more than $11.6 million in claims payments under the NFIP (nearly 45 percent of all claims payments made in Savannah). The average claim amount for these properties is $21,386. Without mitigation, these properties would likely continue to experience flood losses.

The City of Savannah maintains the confidentiality of any personal identifiers associated with repetitive loss property information as provided by FEMA in accordance with the federal Privacy Act of 1974, 5 U.S.C. Section 552(a). As such, the specific address locations and claims history of repetitive loss properties are not described herein. Repetitive loss data is however maintained by City staff to assist with the identification of potential targets for hazard mitigation projects in coordination with willing homeowners. Upon further review and analysis of repetitive loss properties as part of this flood risk assessment, it was determined that 146 of Savannah’s 223 repetitive loss properties (65 percent) are located outside of identified special flood hazards areas. Further, it was determined that the locations of repetitive loss properties are scattered throughout the City of Savannah’s jurisdiction and are not concentrated in easily clustered “repetitive loss areas.”

The City of Savannah coordinates with FEMA on verifying the accuracy of NFIP records for identified repetitive loss properties. As part of this flood mitigation planning effort, FEMA NFIP repetitive loss records were compared with the City’s most recent database for properties acquired and demolished through the Savannah Area Flood Elimination (SAFE) program. The results of this study indicate that there are 26 properties still classified as non-mitigated repetitive loss properties in FEMA records that have since been acquired by the City. The City of Savannah will continue to coordinate with FEMA on updating repetitive loss records as required. The URS Team prepared a detailed inventory of repetitive loss properties in Appendix H which is for official use only to maintain confidentiality per the Privacy Act.

Probability of Future Occurrences

The probability of future flood hazard events in Savannah is certain. While the large-scale, widespread events caused by riverine and coastal flooding are less likely, smaller flash flooding events caused by surface water runoff are highly likely in localized areas of concern. More specific information on the probability of various types and magnitudes of flood hazard occurrences is provided in the next section (see Summary of Flood Hazards in Savannah).

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