Chapter Hazard Analysis Overbank Flooding
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- Bu səhifədəki naviqasiya:
- B Scott Road, Welch Creek, July 20, 1996
- Post-flood silt, mold and mildew
- Building damage
- Effects of soaking on walls, floors and cabinets
- Soaking damages most household contents
- Damage data
- Subbasin Buildings Estimated Damage
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arning and evacuation: The threat to life posed by a flood can be avoided if people can evacuate before the waters reach their buildings or close their evacuation routes. This requires advance notice that a flood is coming and a system to disseminate flood warnings. Flood warning programs are discussed in Chapter 7. Only on the Fox River is there enough lead time to allow protective steps, such as sandbagging, to be taken. Other, smaller, streams rise so fast during a heavy local rain, that expensive systems of remote rain and stream gages would be needed to provide adequate notice to emergency managers. Even then, there would be little time for people to do much more than escape to high ground. B 
Scott Road, Welch Creek, July 20, 1996 Source: Chris Dagiantis, Kane County Development Department ridges: A key evacuation and safety concern is when roads and bridges go under water. Generally, the larger the road, the more likely it will not flood, but this is not always the case (witness the interstate highway under water in the photo on page 2-9). A review of the Flood Insurance Rate Map and accompanying flood profiles identified 58 bridges and culverts that will be underwater during a base flood. These are shown in Map 1-10 in Chapter 1. They are listed in Appendix D. A bridge does not have to be under water to be damaged or to cut off an evacuation route. In some cases the bridge is high, but the access road may be flooded. In other cases, the bridge or culvert can be washed out. This is especially dangerous if a person drives on a flooded road and assumes that the bridge is still there. In addition to the locations listed in Appendix D, there are bridges and culverts in areas that are not included in the Flood Insurance Rate Map study areas, such as those located along small tributary streams. The following have been identified by the municipalities and township road commissions as obstructing or impeding the flow water during flood events:
Health: While such problems are often not reported, three general types of health hazards accompany floods. The first comes from the water itself. Floodwaters carry whatever was on the ground that the upstream runoff picked up, including dirt, oil, animal waste, and lawn, farm and industrial chemicals. Pastures and areas where cattle and hogs are kept can contribute polluted waters to the receiving streams. Flood waters saturate the ground which leads to infiltration into sanitary sewer lines. When wastewater treatment plants are flooded, there is nowhere for the sewage to flow. Infiltration and lack of treatment lead to overloaded sewer lines which back up into low lying areas and some homes. Even though diluted by flood waters, raw sewage can be a breeding ground for bacteria, such as e coli, and other disease causing agents. Because of this threat, the Kane County Health Department gave tetanus shots to people affected by the July 1996 flood. The City of Batavia gave shots to its employees. The second type of health problem comes after the water is gone. Stagnant pools become breeding grounds for mosquitoes, and wet areas of a building that have not been cleaned breed mold and mildew. A building that is not thoroughly and properly cleaned becomes a health hazard, especially for small children and the elderly. The Kane County Health Department states that some people have reported upper respiratory problems that they believe are caused by molds that grew after the July 1996 flood. A 
Post-flood silt, mold and mildew nother health hazard occurs when heating ducts in a forced-air system are not properly cleaned after inundation. When the furnace or air conditioner is turned on, the sediments left in the ducts are circulated throughout the building and breathed in by the occupants. If the water system loses pressure, a boil order may be issued to protect people and animals from contaminated water. Following the July 1996 flood, the Kane County Health Department tested private wells in rural areas and distributed bottled water to their owners. The third problem is the long-term psychological impact of having been through a flood and seeing one’s home damaged and irreplaceable keepsakes destroyed. The cost and labor needed to repair a flood-damaged home puts a severe strain on people, especially the unprepared and uninsured. There is also a long-term problem for those who know that their homes can be flooded again. The resulting stress on floodplain residents takes its toll in the form of aggravated physical and mental health problems. “These follow-up studies show a consistent pattern of increased psychological problems among flood victims for up to 5 years after the flood. The findings regarding non-psychiatric morbidity are less consistent, but many of the reported morbidity problems such as hypertension and cardiovascular disease-and even leukemia and lymphoma-may be stress related.” – The Public Health Consequences of Disasters, page 74. Following the July 1996 flood, 16 shelters were opened to house displaced families. Another measure of the impact on people and the disruption flooding causes is applications for Federal disaster assistance. After the July 1996 flood, 6,568 Kane County families applied for various types of individual assistance, such as temporary housing and “unmet needs,” i.e., funds needed for things that insurance and other sources of assistance do not provide. In Kane, DuPage and Kendall Counties, the American Red Cross opened eleven service centers to assist families following the July 1996 flood. Over the course of the flood and the recovery, the Red Cross served over 43,000 meals to families, workers and volunteers. The total cost to the Red Cross temporary housing, meals, and other assistance was in excess of $1.2 million. Three deaths were associated with the July 1996 disaster. Three people were hospitalized and 65 people were injured as a result of the flood. Building damage: In a few situations, deep or fast moving waters will push a building off its foundation, but this is rare and Kane County has few areas where the depths and velocities are that high. More often, structural damage is caused by the weight of standing water, known as “hydrostatic pressure.” Basement walls and floors are particularly susceptible to damage by hydrostatic pressure. Not only is the water acting on basement walls deeper, a basement is subjected to the combined weight of water and saturated earth. In addition, water in the ground underneath a flooded building will seek its own level, resulting in uplift forces that can break a concrete basement floor. D
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Soaking damages most household contents oaking can cause extensive damage to household goods. Wooden furniture may become so badly warped that it cannot be used. Other furnishings such as upholstery, carpeting, mattresses, and books usually are not worth drying out and restoring. Electrical appliances and gasoline engines will not work safely until they are professionally dried and cleaned. In short, while a building may look sound and unharmed after a flood, the waters can cause a lot of damage. As shown in the above photo, to properly clean a flooded building, the walls and floors should be stripped, cleaned, and allowed to dry before being recovered. This can take weeks and is expensive. Damage data: The number of buildings exposed to overbank flooding is shown in the table on page 2-18. One source of building damage data is the flood studies conducted for several watersheds. In addition to providing estimates of historical damage, these studies produced predicted damage estimates. The 1986 “Floodplain Management Study – Indian Creek and Tributaries” produced the data in the table below for the 1983 flood on Indian Creek and its tributaries. The study estimated that the watershed had average annual damage of $595,800 with 156 buildings at risk for the 100-year event. While, this includes portions of DuPage County, all property damage was located in the Kane County portion of the watershed.
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