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<br />The Corps' regulations for multipurpose reservoirs
<br />in the West require more storage space to
<br />be reserved for flood control during fhe late fall
<br />and winter months. In spring there is less flood
<br />risk (except for rare years of heavy snowpack in
<br />the southern Sierra), As the need for flood space
<br />diminishes, reservoirs are filled with snow melt
<br />that is allocated during California's long, dry
<br />summers.
<br />
<br />The amount of outflow from reservoirs is usually
<br />regulated by balancing the remaining reservoir
<br />storage space, the expectation of additional inflow
<br />and downstream flow rates. Some multipurpose
<br />dams are geared more toward flood control and
<br />others for water storage. And there are times when
<br />the two needs coli ide,
<br />
<br />Following the subtropical series of storms that hit
<br />California in January 1997, flood managers released
<br />record outflows from several of the reservoirs to
<br />avoid uncontrolled spills, The months following the
<br />floods were some of the driest on record. The
<br />reservoirs did not fill and the Bureau had to reduce
<br />water deliveries.
<br />
<br />Both the 1986 and 1997 tloods led to a reassess.
<br />ment of the hydraulic assumption defining the
<br />100-year flood event, which refers to the likelihood
<br />and not the frequency of a storm, (A 100-year flood
<br />event is defined as a 1 percent chance of being
<br />equaled or exceeded in any given year. Two or more
<br />100'year floods could occur in consecutive years
<br />or within the same year, or not occur at all for
<br />many years,) Critics point out that the current
<br />definition ignores site specific threats and is based
<br />on weather records from the first half of the century,
<br />when conditions were milder.
<br />
<br />The record storm of 1986 revealed an under.design
<br />of needed flood space in Folsom Reservoir and
<br />exposed deficiencies in many of the levees around
<br />Sacramento, The hydrologic history used to gauge
<br />the probable size of future floods was reevaluated
<br />and Folsom was found to protect only against a
<br />63-year storm, Flood management policies were
<br />revised and Folsom Reservoir was reoperated to
<br />provide a 1 aD-year level of protection. Since 1986,
<br />there has been an ongoing levee rehabilitation
<br />program that targets population centers along the
<br />American and Sacramento rivers.
<br />
<br />In a 1998 hydrology report, the Corps found high
<br />flows will occur more frequently than previously
<br />thought. Its reevaluation gives Sacramento only
<br />about a 77-year level of protection,
<br />
<br />How TO PREPARE FOR FLOODS
<br />
<br />
<br />If you live in a flood-prone area, get ready today:
<br />. Itemize your personal property. Photos will help you to make a claim,
<br />
<br />. Learn the safest route from your home to high ground,
<br />
<br />. Keep a battery-powered radio, emergency cooking equipment and flashlighfs
<br />accessible and in working order.
<br />
<br />. Buy flood insurance. Most homeowner's policies do not cover damages from
<br />floods, However, residents in many areas are eligible for federally subsidized
<br />flood insurance rates, Check with your property/casualty agent, or check FEMA
<br />maps to see if your home is in a flood zone,
<br />
<br />If the Flood Comes:
<br />. Consider your family's safety before you worry about possessions,
<br />
<br />. Tune your battery'powered radio to an emergency station tor insfrucfions,
<br />
<br />. If you're caught in a building, take warm clothing, radio and flashlight and
<br />move to the second floor or roof, DO NOT attempt to swim, Wait for help,
<br />
<br />. Avoid flooded areas, Do not try to walk through water more than knee deep,
<br />
<br />. If time permits, turn off utilities and move valuables to higher elevations.
<br />
<br />. If it is safe to evacuate by car, take with you canned food, water, blankets, first
<br />aid kit, flashlights, dry clothing and any medications your family may need,
<br />
<br />. Do not drive where water is over the road - the road may be washed out.
<br />
<br />. If your car stalls in a flooded area, abandon it as soon as possible,
<br />
<br />After the Flood:
<br />. Before entering a building, check for structural damage, If you smell gas, turn
<br />off the outside gas lines at the meter, and let the building air out for an hour,
<br />Do not use a flame as a source of Iighf since gas may still be trapped inside,
<br />
<br />. Turn off the main electrical power switch. Do not use electricity until the system
<br />has been checked by the electric utility or an electrician,
<br />
<br />. Until your drinking water system has been declared safe, boil water for drink-
<br />ing and food preparation tor 10 minutes prior to use, Or mix 1/2 teaspoon
<br />liquid laundry bleach with 2.1/2 gallons of water and let stand for 30 minutes,
<br />
<br />. Take wooden furniture outside, but keep it out of direct sun to prevent warping.
<br />
<br />. Shovel mud out while it is still moist to allow the walls and floors to dry,
<br />
<br />. Remove mildew with a solution of 4 to 6 tablespoons of trisodium phosphate
<br />(TSP), 1 cup chlorine bleach and 1 gallon water,
<br />
<br />. Flooded basements should be drained and cleaned as soon as possible, but
<br />to avoid structural damage drain only one-third the volume of water each day,
<br />
<br />Adapted from the FEMA publication In the Event 01 a Flood,
<br />
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