3/22/2023 0 Comments 18 the hit list 1993![]() Relation varies for each location and is affected by many factors. Therefore, a conversion between discharge and stage is necessary. In addition, river stages are far easier for the public toĬomprehend. While model computations are based on flow volumes, most river observations are onlyĪvailable as river stages. This time step lends itself to data availability, i.e., 6-hourly synopticĪ storm hydrograph is determined by combining 6-hour incremental runoff values. Surface runoff occurs in a given time period, e.g., 6 hours. A unit hydrograph, to be used inĬonjunction with an event API model, is best derived from a single rainfall event when all Constant physical characteristics across the basin and similar hydrograph shapesįrom storms with uniform rainfall patterns are assumed. That represents 1 inch of runoff from rain falling uniformly over a specific basin for a given The unit hydrograph is an empirical normalization Runoff from the soil moisture model becomes input for the flow model. This feature allows hydrologists to make timelyĭecisions in balancing the observed physical response with model computed results. Lends itself to quick operational adjustments. Limitation is that baseflow is not addressed directly. The assumption is thatĭuring periods of no precipitation, soil moisture decreases logarithmically. Physical limitations, the API model has a relatively short memory. Plus rain becomes input for the soil moisture model. Precipitation is rain or snow based on temperature input. Temperature data are input into a snow model. Various components are involved in the preparation of flood forecasts. Boundaries of National Weather Service RFCs Of 1993 computes a daily index of soil moisture, considers additional rainfall, and computesįigure 2. The API model used during The Great Flood The amount of actual rainfall from the event. A given API value at theīeginning of a rain event is typically related to the week of the year, the storm duration, and Hydrologists at NWS RFCsĭeveloped API procedures based on historical storm events. (RFC) to produce flood crest forecasts since the 1940s (Fig.2). The soil moisture model in primary use was the Antecedent Precipitation Index (API) model.ĪPI models have been used in most National Weather Service (NWS) River Forecast Centers Water treatment plants were destroyed (Larson, 1993). All railroad traffic in the Midwest was halted. Numerous interstate highways and other roads were closed. Missouri River, bridges were out from Kansas City, downstream to St. Mississippi River from Davenport, Iowa, downstream to St. Bridges were out or not accessible on the Barge traffic on the Missouri and Mississippi Inundated, some of which may not be useable for years to come. At least 15 million acres of farmland were Towns totally and completely under flood waters. Least 10,000 homes were totally destroyed, hundreds of towns were impacted with at least 75 Tens of thousands of people were evacuated, some never to return to their homes. Most significant flood event ever to occur in the United States (Fig. Nearly 150 major rivers and tributaries were affected. River forecast points in the Midwestern United States were above flood stage at the same The magnitude and severity of this flood event was simply over-whelming, and it ranksĪs one of the greatest natural disasters ever to hit the United States. Levees failed along the Mississippi and Missouri Rivers. Fifty flood deaths occurred, and damages approached $15 billion. National Weather Service and the precipitation events which caused the flood.įrom May through September of 1993, major and/or record flooding occurred across Northĭakota, South Dakota, Nebraska, Kansas, Minnesota, Iowa, Missouri, Wisconsin, and The paper discusses some details of the flood, the forecasting procedures utilized by the Impacted, and the length of the time the flood was an issue. Theįlood was unusual in the magnitude of the crests, the number of record crests, the large area Hundreds of levees failed, and thousands of people were evacuated, some for months. Damages totaled $15 billion, 50 people died, The 1993 midwest flood was one of the most significant and damaging naturalĭisasters ever to hit the United States. Destructive Water: Water-Caused Natural Disasters - Their Abatement and ControlĪbstract. ![]()
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