Shifting Economic Impacts from Weather Extremes in the United States: A Result of Societal Changes,Not Global Warming

Loss values from extremes in the U.S. and elsewhere have been more qualitativethan quantitative, but recent pressures for better information have led to newassessments and better estimates of financial losses from extremes. These pressureshave included concerns over potential impacts of more extremes due to global warmingfostered by ever increasing costs to the insurance industry and government from weather extremes; plus a series of massive losses during the past 15 years (drought of 1988–1989,Hurricane Andrew in 1992, and Midwestern 1993 floods). These recent assessmentsattempted to adjust data for societal changes over time and thus derived new and betterestimates of losses for seven major extremes than existed previously. Three extremeshave annual average losses in excess of a billion dollars (1998 dollars) includinghurricanes ($4.2 billion), floods ($3.2 billion), and severe local storms ($1.6 billion).One extreme and its adjusted losses exhibit upward trends (floods), but all others showno increases with time or temporal decreases (hail, hurricanes, tornadoes, and severethunderstorms). Annual national losses during 1950–1997 from the three major extremes, plus four others (hail, tornadoes, winter storms, and wind storms), collectively reveal no upward or downward trend over time, with an average annual loss of $10.3 billion. The quality loss values do not indicate an increase as has been postulated for global warming. The good news is that better estimates of impacts now exist, but the bad news is that they are still estimates and do not include sizable unmeasured losses. If accurate data on the economic impacts from weather extremes are seen as important for scientific research and policy-making for global warming, the U.S. needs a continuing program to adequately measure losses from weather extremes.     

Record-High Losses for Weather Disasters in the United States During the 1990s: How Excessive and Why?

During 1990–1996 the United States experienced record-setting insured property losses due to numerous weather catastrophes, each event causing $100 million or more in losses (1991 dollars). The total loss in this 7-year period, after adjustment to inflation and other factors, was $39.65 billion with $15 billion coming from one event, Hurricane Andrew. In the 1990s, 72 catastrophes occurred, half of the total number in the 40 preceding years, 1950–1989. Although the total loss and the number of catastrophes were exceptionally high in the 1990s, the average loss per event was $551 million, only slightly more than the $467 million average for catastrophes during 1950–1989. Furthermore, storm intensities in the 1990s were slightly less than those during the preceding 40 years, revealing the excess losses of the 1990s to be a result of an extremely large number of damaging storms causing losses exceeding $100 million. Examination of historical values of most weather extremes including hurricanes, floods, and tornadoes, did not show an increase during the 1990s, revealing that weather changes were not the principal cause of more catastrophes. Examination of recent demographic shifts in the U.S. reveals two changes, each based on major re-locations to higher-valued property concentrated in areas either with a high frequency of damaging storms (Gulf and East Coast), or to where even a small but intense storm can cause huge losses (urban areas and West Coast). These shifts, plus the continuing growth of population in other storm-prone areas have greatly increased society's vulnerability to storm damage. An in-depth analysis of many conditions was required to establish that the high losses and numerous catastrophes of the 1990s were largely the result of societal changes and not major weather changes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Characteristics of severe Atlantic hurricanes in the United States: 1949–2006

Property insurance data available for 1949–2006 were assessed to get definitive measures of hurricane losses in the U.S. Catastrophes, events causing >$1 million in losses, were most frequent in the Southeast and South climate regions. Losses in these two regions totaled $127 billion, 85% of the nation’s total losses. During the period 1949–2006 there were 79 hurricane catastrophes, causing $150.6 billion in losses and averaging $2.6 billion per year. All aspects of these hurricanes showed increases in post-1990 years. Sizes of loss areas averaged one state in 1949–1967, but grew to 3 states during 1990–2006. Seven of the ten most damaging hurricanes came in 2004 (4) and 2005 (3). The number of hurricanes also peaked during 1984–2006, increasing from an annual average of 1.2 during 1949–1983 to 2.1 per year. Losses were $49.3 billion in 1991–2006, 32% of the 58-year total. Various reasons have been offered for such recent increases in hurricane losses including more hurricanes, more intense tropical storms, increased societal vulnerability in storm-prone areas, and a change in climate due to global warming, although this is debatable.     

Hummocky cross-stratification, tropical hurricanes, and intense winter storms

Most previous workers have inferred a storm origin for hummocky cross-stratification, which typically occurs in shallow-marine deposits. On the modern Earth, the only storms capable of profoundly affecting shallow-marine depositional environments are severe tropical cyclones (hurricanes) and mid-latitude winter wave cyclones (intense winter storms). This paper examines the palaeogeographic distribution (including palaeolatitude and palaeogeographic setting) of 107 occurrences of hummocky cross-stratification, ranging in age from the Proterozoic to Recent. In each of these stratigraphic units, both palaeolatitude and palaeogeography are consistent with a direct storm influence (associated with the passage of hurricanes or winter storms directly over the site of deposition). This palaeogeographic evidence lends support to the inferred storm origin for hummocky cross-stratification; further, the distribution of the structure suggests that most occurrences (73%) were generated by tropical hurricanes, the remaining 27% being generated by intense mid-latitude winter storms. The preferential generation of hummocky cross-stratification by hurricanes is consistent with: (1) the known differences in the nature of the bottom flows generated by the two major storm types, and (2) the inferred nature of the flows which form hummocky cross-stratification. Hurricanes couple less effectively with the water column than do intense winter storms. Due to this ineffective coupling, hurricane-generated bottom flows tend to be oscillatory-or multidirectional-dominant, with only minor unidirectional components of motion. In contrast, intense winter storms generally do couple effectively with the water column, generating bottom flows which possess a dominant or significant unidirectional component. Most previous workers have suggested that hummocky cross-stratification forms under oscillatory- or multidirectional-dominant flow; thus, it is conceptually reasonable that the vast majority of ancient occurrences of hummocky cross-stratification were probably hurricane-generated, as suggested by the aforementioned palaeogeographic distribution. The Proterozoic, Palaeozoic, Neogene, and Quaternary were times when global climate was similar to that of today. The distribution of hummocky cross-stratification deposited during these times suggests that both hurricanes and intense winter storms occupied latitudinal belts during these times which were essentially identical to those occupied by their modern counterparts. The Mesozoic and Palaeogene were non-glacial times when global climate was much warmer than that of today. The distribution of hummocky cross-stratification deposited during this interval suggests that hurricanes occurred more frequently at higher latitudes during non-glacial times than they do at present. The possibility of a broadened hurricane belt during the Mesozoic and Palaeogene is consistent with climatic considerations. A limited number of Mesozoic and Palaeogene rock units containing hummocky cross-stratification were deposited in palaeogeographic settings that preclude a direct hurricane influence; these examples were deposited in the middle latitudes, suggesting that intense winter storms continued to form hummocky cross-stratification in the middle latitudes during these much warmer times. Some previous workers have suggested that tsunamis may be capable of generating hummocky cross-stratification. The palaeogeographic distribution of the structure does not support an origin due to tsunamis. Lacustrine examples of hummocky cross-stratification reported herein are the first known non-marine occurrences; they suggest that storm effects strongly influence the sedimentary record of some lakes.     

Windstorms in the United States

High winds are one of the nation’s leading damage-producing storm conditions. They do not include winds from tornadoes, winter storms, nor hurricanes, but are strong winds generated by deep low pressure centers, by thunderstorms, or by air flow over mountain ranges. The annual average property and crop losses in the United States from windstorms are $379 million and windstorms during 1959–1997 caused an average of 11 deaths each year. Windstorms range in size from a few hundred to hundreds of thousands square kilometers, being largest in the western United States where 40% of all storms exceed 135,000 km². In the eastern United States, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western US point averages are 1.9. Midwestern states average between 15 and 20 wind storms annually; states in the east average between 10 and 25 storms per year; and West Coast states average 27–30 storms annually. Storms causing insured property losses >$379 million and windstorms during 1959–1997 caused an average of 11 deaths each year. Windstorms range in size from a few hundred to hundreds of thousands square kilometers, being largest in the western United States where 40% of all storms exceed 135,000 km². In the eastern United States, windstorms occur at a given location, on average, 1.4 times a year, whereas in the western US point averages are 1.9. Midwestern states average between 15 and 20 wind storms annually; states in the east average between 10 and 25 storms per year; and West Coast states average 27–30 storms annually. Storms causing insured property losses >1 million, labeled catastrophes, during 1952–2006 totaled 176, an annual average of 3.2. Catastrophic windstorm losses were highest in the West and Northwest climate regions, the only form of severe weather in the United States with maximum losses on the West Coast. Most western storms occurred in the winter, a result of Pacific lows, and California has had 31 windstorm catastrophes, more than any other state. The national temporal distribution of catastrophic windstorms during 1952–2006 has a flat trend, but their losses display a distinct upward trend with time, peaking during 1996–2006.     

Hurricanes 2004: An overview of their characteristics and coastal change

Four hurricanes battered the state of Florida during 2004, the most affecting any state since Texas endured four in 1884. Each of the storms changed the coast differently. Average shoreline change within the right front quadrant of hurricane force winds varied from 1 m of shoreline advance to 20 m of retreat, whereas average sand volume change varied from 11 to 66 m³ m⁻¹ of net loss (erosion). These changes did not scale simply with hurricane intensity as described by the Saffir-Simpson Hurricane Scale. The strongest storm of the season, category 4 Hurricane Charley, had the least shoreline retreat. This was likely because of other factors like the storm's rapid forward speed and small size that generated a lower storm surge than expected. Two of the storms, Hurricanes Frances and Jeanne, affected nearly the same area on the Florida east coast just 3 wk apart. The first storm, Frances, although weaker than the second, caused greater shoreline retreat and sand volume erosion. As a consequence, Hurricane Frances may have stripped away protective beach and exposed dunes to direct wave attack during Jeanne, although there was significant dune erosion during both storms. The maximum shoreline change for all four hurricanes occurred during Ivan on the coasts of eastern Alabama and the Florida Panhandle. The net volume change across a barrier island within the Ivan impact zone approached zero because of massive overwash that approximately balanced erosion of the beach. These data from the 2004 hurricane season will prove useful in developing new ways to scale and predict coastal-change effects during hurricanes.     

Possible effects of the 2004 and 2005 hurricanes on manatee survival rates and movement

Prior research on manatee (Trichechus manatus latirostris) survival in northwest Florida, based on mark-resighting photo-identification data from 1982–1998, showed that annual adult apparent survival rate was significantly lower during years with extreme storms. Mechanisms that we proposed could have led to lower estimates included stranding, injury from debris, being fatally swept out to sea, or displacement into poorly monitored areas due to storm-generated longshore currents or storm-related loss of habitat. In 2004 and 2005, seven major hurricanes impacted areas of Florida encompassing three regional manatee subpopulations, enabling us to further examine some of these mechanisms. Data from a group of manatees tracked in southwest Florida with satellite transmitters during Hurricanes Charley, Katrina, and Wilma showed that these animals made no significant movement before and during storm passage. Mark-resighting data are being collected to determine if survival rates were lower with the 2004 and 2005 storms.     

RETRACTED ARTICLE: Space and time distributions of major winter storms in the United States

Winter storms are a major weather problem in the United States and their losses have been rapidly increasing. A total of 202 catastrophic winter storms involving ice storms, blizzards, and snowstorms, each causing >$5 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous United States, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of nine storms, and one year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.     

Influence of stress conditions on shear behavior of slip zone soil in ring shear test: an experimental study and numerical simulation

Natural Hazards - Hurricanes and tropical storms pose a significant threat to developed coastal regions around the world. In the United States, hurricanes cause billions of dollars in damage each...     

Storms of tropical origin: a climatology for New York State,USA (1851–2005)

The tropical storm database used in this study was obtained from the National Oceanic and Atmospheric Administration’s (NOAA) Coastal Service Center, using the Historical Hurricane Tracks tool. Queries were used to determine the number of storms of tropical origin that have impacted the State and each of its counties. A total of 76 storms of tropical origin passed over New York State between 1851 and 2005. Of these storms, 14 were classified as hurricanes. The remaining hurricanes passed over New York State as weaker or modified systems—27 tropical storms, 7 tropical depressions, and 28 extratropical storms (ET). Long Island experiences a disproportionate number of hurricanes and tropical storms. The average frequency of hurricanes and storms of tropical origin (all types) is one in every 11 years and one in every 2 years, respectively. September is the month of greatest frequency for storms of tropical origin, although the storms of greatest intensity tend to arrive later in the hurricane season and follow different poleward tracks. While El Nino Southern Oscillation (ENSO) cycles appear to show some influence, the frequency and intensity of storms of tropical origin appear to follow a multidecadal cycle. Storm activity was greatest in both the late 19th and 20th centuries. During periods of increased storm frequency and intensity storms reached New York State at progressively later dates. While the number and timing of storms of tropical origin is likely to increase, this increase appears to be attributed to a multidecadal cycle, as opposed to a trend in global warming.     

A Spatial and Temporal Analysis of Damaging Snowstorms in the United States

Records of very damaging snowstorms, those causing more than $25 million in property losses, across the United States were assessed to define the spatial and temporal dimensions of the nation’s snowstorm activity during 1949–2000. In this 52-year period 155 snowstorms occurred and caused losses totaling $21.6 billion (2000 dollars). The northeastern U.S. had the nation’s maximum storm occurrences (79 storms), total losses ($7.3 billion), and storm intensity. Two-thirds of all U.S. losses occurred in the Northeast, Southeast, and Central climate regions, and storm occurrences and losses were least in the western U.S. The incidence of storms peaked in the 1976–1985 period and exhibited no up or down trend during 1949–2000. However, national losses had a significant upward time trend, as did storm sizes and intensity. States with the greatest number of storms were New York (62) and Pennsylvania (58) with only 2 storms in Montana, Idaho, and Utah. Storm losses in the northeastern and southeastern U.S. had U-shaped time distributions with flat time trends for 1949–2000, but losses in the western regions and Deep South had distinct upward trends in losses and storm size. More than 90% of all storm losses in the western U.S. occurred after 1980. These findings indicating increased losses over time reflect that a rapidly growing population and vulnerability of more property at risk have been major factors affecting losses, and the lack of a change over time in snowstorm incidences suggests no change in climate during 1949–2000.     

Probabilistic winter storm risk assessment for residential buildings in Germany

Losses resulting from winter storms contribute a significant part to the overall losses among all natural hazards in most mid-latitude European countries. A realistic assessment of storm risk is therefore essential for prevention and coping measures. The paper presents a framework for probabilistic storm risk assessment for residential buildings which is exemplarily performed for Germany. Two different approaches are described, and results are presented. The hazard-based approach brings together hazard, vulnerability and building assets to calculate risk curves for each community. The storm-based approach uses loss information from past storm events to calculate statistical return periods of severe storms. As a result, a return period of 83 years to the most severe storm series in 1990 is calculated. Average annual losses of €170 million to residential buildings are calculated for all over Germany. The study demonstrates how the approaches complement each other and how validation is performed.     

Productivity and Resilience: Long-Term Trends and Storm-Driven Fluctuations in the Plant Community of the Accreting Wax Lake Delta

River deltas are dynamic geologic features where the plant community engages in critical feedbacks with geomorphology, and plant community development is impacted by both riverine and coastal drivers. A vegetation index (NDVI) calculated from a time series of 54 peak growing season Landsat-5 TM and Landsat-7 ETM+ images was used to assess the long-term trends and storm event-driven changes in the vegetation community associated with the Wax Lake Delta, an actively accreting subdelta of the Mississippi River. Multiple regression models were developed to explain variation in the vegetated area of the delta and mean delta NDVI from 1984 to 2011 as a function of date, hydrology, and seasonality. The models indicate that both vegetated area and mean NDVI increased over time from 1984 to 2011. Productivity measures following Hurricanes Lili (2002), Rita (2005), and Ike (2008) represented statistical outliers; significant decreases in NDVI following these storms suggest that hurricanes passing directly over or to the west of the delta result in short-term disturbance to the plant community, most likely related to saltwater intrusion associated with storm surge. However, in each case, both vegetated area and mean NDVI recovered to the long-term trend by the following growing season. These results demonstrate that the freshwater marshes within this mineral-rich, accreting delta are increasing in productivity as the delta matures and are extremely resilient to coastal storm disturbance.     

Urban hailstorms: a view from Alberta

Urban hailstorms are rarely studied in detail. This work documents five urban storms in Alberta where damage has, on three occasions, set the record for Canada's most costly natural disaster. Information from newspapers, insurance companies, and disaster assistance programs was utilized to supplement meteorological records and information obtained from public surveys.The record-breaking hail swath which accompanied the 1987 Edmonton tornado was mapped using over 800 responses to an unprecedented newspaper survey. Tennis ball sized hail struck 125 km² of the city. Record-sized hailstones for Alberta were collected. Citizens' measurements of giant hailstones were compared to laboratory measurements. The rural storms were tracked using lightning detector information and damage was mapped using crop insurance and disaster assistance claims. The tornado-bearing storm was found to have a unique track.A late-season hailstorm which struck Calgary in 1991 was mapped using homeowner insurance claims organized by postal areas. Nine out of thirty areas had claims rates exceeding 50%, mainly for shingle replacement. Experiences of claims adjustors and an informal public survey were also utilized. Rural storms were mapped using weather radar and crop losses. The radar beam was strongly attenuated when it passed through hail-bearing storms and, thus, its ability to detect large hail was compromised.Weather conditions, urban and rural damaged areas, and insurance payments were compared for all five local hailstorms. These storms were discussed within the context of the long history of Alberta hail research and current trends in technology implementation. Forecasting of these hailstorms using conventional severe weather indicators was difficult in Calgary because of that city's proximity to the mountains. Hailstorms that struck Munich, Denver, and Toowoomba (Australia) were also discussed, and the hailstones collected from the great Munich storm were compared to those collected from the Edmonton storms.     

Storm catastrophes in the United States

A unique historical data set describing the 142 storms each producing losses in excess of $100 million in the United States during the 1950–89 period were analyzed to describe their temporal characteristics. The storms caused $66.2 billion in losses (in 1991 values), 76% of the nation's insured storm losses in this period. These extreme storm catastrophes (SCs) were most prevalent in the south, southeast, northeast, and central U.S., with few in and west of the Rocky Mountains. Storm incidences were high in the 1950s, low in the 1960s-early 1970s, and increased in the 1980s. Losses due to SCs peaked in the 1950s, again in the late 1960s, with a lesser peak after 1985. The areal extent of storm losses peaked after 1975 and was least in the 1960s. The temporal variations of the three storm measures (incidence, losses, and extent) did not agree except when they all peaked in the 1950s. Regionally-derived time distributions of SCs showed a marked north-south differences in the United States with a U-shaped 40-year distribution in the northern half of the nation, and a relatively flat trend until a peak in the 1980s in the southern regions. The temporal distributions of hurricane-caused catastrophes differed regionally with occurrences in the prime areas, the southern, southeastern, and northeastern U.S., each quite different. Temporal distributions of thunderstorm and winter storm catastrophes were regionally more uniform.     

Losses from sleet storms in the United States

Increasing losses of life and property and damages to the environment due to sleet and related winter storm conditions have increased the need for long-term sleet storm data to better assess the point and regional risks of sleet and their long-term variations. The areas of greatest losses and frequency of catastrophes caused by sleet during 1971–2007 are the Northeast and Central regions of the U.S. These two regions experienced 72% of all the nation’s sleet losses. Most of the western U.S. had no damaging sleet-related events or losses. When sleet losses occurred, they tended to be in 2, 3, or 4 adjacent states. Sleet catastrophes were most common in January with 15 of the 30 events. The earliest storm occurred in October and the latest in March. The temporal distributions of catastrophes and their losses during 1971–2007 were similar. Both showed a secondary peak in 1976–1979, a low in 1988–1991, and then high values during the 1996–2007 period. The temporal distributions of damaging storms and losses indicate an upward trend over time.     

Spatially explicit mapping of hurricane risk in New England, USA using ArcGIS

Hurricanes are one of the major natural disturbances affecting human livelihoods in coastal zones worldwide. Assessing hurricane risk is an important step toward mitigating the impact of tropical storms on human life and property. This study uses NOAA’s historical tropical cyclone database (HURDAT or ‘best-track’), geographic information systems, and kernel smoothing techniques to generate spatially explicit hurricane risk maps for New England. Southern New England had the highest hurricane risk across the region for all storm intensities. Long Island, western Connecticut, western Massachusetts, and southern Cape Cod, Martha’s Vineyard, and Nantucket had high storm probabilities and wind speeds. Results from this study suggest that these locations may be of central importance for focusing risk amelioration resources along the Long Island and New England coastlines. This paper presents a simple methodology for hurricane risk assessment that could be applied to other regions where long-term spatial storm track data exist.     

Evaluation of coastal inundation hazard for present and future climates

Coastal inundation from hurricane storm surges causes catastrophic damage to lives and property, as evidenced by recent hurricanes including Katrina and Wilma in 2005 and Ike in 2008. Changes in hurricane activity and sea level due to a warming climate, together with growing coastal population, are expected to increase the potential for loss of property and lives. Current inundation hazard maps: Base Flood Elevation maps and Maximum of Maximums are computationally expensive to create in order to fully represent the hurricane climatology, and do not account for climate change. This paper evaluates the coastal inundation hazard in Southwest Florida for present and future climates, using a high resolution storm surge modeling system, CH3D-SSMS, and an optimal storm ensemble with multivariate interpolation, while accounting for climate change. Storm surges associated with the optimal storms are simulated with CH3D-SSMS and the results are used to obtain the response to any storm via interpolation, allowing accurate representation of the hurricane climatology and efficient generation of hazard maps. Incorporating the impact of anticipated climate change on hurricane and sea level, the inundation maps for future climate scenarios are made and affected people and property estimated. The future climate scenarios produce little change to coastal inundation, due likely to the reduction in hurricane frequency, except when extreme sea level rise is included. Calculated coastal inundation due to sea level rise without using a coastal surge model is also determined and shown to significantly overestimate the inundation due to neglect of land dissipation.     

Effects of two hurricanes onSyringodium filiforme, manatee grass, within the Loxahatchee River estuary, Southeast Florida

In September 2004, the Loxahatchee River Estuary was affected by Hurricanes Frances and Jeanne, which resulted in a monthly rainfall record of 610 mm and abnormally high freshwater discharges to the system. The occurrence, density, and biomass ofSyringodium filiforme in the Loxahatchee River Estuary declined significantly following the September 2004 storms based on 15 mo of pre-hurricane monitoring and 12 mo of post-hurricane monitoring. Throughout posthurricane monitoring,S. filiforme showed no sign of recovery, thoughHalophila johnsonii increased considerably during the post-hurricane period. Freshwater discharges resulting from the September 2004 hurricanes lowered minimum daily salinity values to near zero and increased standard deviation of daily salinity values to 11‰. Extremely low minimum daily salinity values and high daily salinity fluctuations likely resulted in the observed decline ofS. filiforme. We advise the use of minimum daily salinity values when assessing seagrass habitat suitability or when modeling the effects of alternative water management scenarios.     

Impact of hurricanes storm surges on the groundwater resources

Ocean surges onto coastal lowlands caused by tropical and extra tropical storms, tsunamis, and sea level rise affect all coastal lowlands and present a threat to drinking water resources of many coastal residents. In 2005, two such storms, Hurricanes Katrina and Rita struck the Gulf Coast of the US. Since September 2005, water samples have been collected from water wells impacted by the hurricanes’ storm surges along the north shore of Lake Pontchartrain in southeastern Louisiana. The private and public water wells tested were submerged by 0.6–4.5 m of surging saltwater for several hours. The wells’ casing and/or the associated plumbing were severely damaged. Water samples were collected to determine if storm surge water inundated the well casing and, if so, its effect on water quality within the shallow aquifers of the Southern Hills Aquifer System. In addition, the samples were used to determine if the impact on water quality may have long-term implication for public health. Laboratory testing for several indicator parameters (Ca/Mg, Cl/Si, chloride, boron, specific conductance and bacteria) indicates that surge water entered water wells’ casing and the screened aquifer. Analysis of the groundwater shows a decrease in the Ca/Mg ratio right after the storm and then a return toward pre-Katrina values. Chloride concentrations were elevated right after Katrina and Rita, and then decreased downward toward pre-Katrina values. From September 2005 to June 2006, the wells showed improvement in all the saltwater intrusion indicators.