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<br />D. Step 2 - TrllDSld.t Data <br />Various types of communications systems are used to transmit data. In manual <br /> <br /> <br />local flood warning systems, information is generally transmitted by telephone <br /> <br /> <br />land lines, CB radio, or ham operators. Automated systems use UHF, VHF, or <br /> <br /> <br />microwave radio transmission, meteor burst telemetry, or satellites. <br /> <br />. <br /> <br />. <br /> <br />Data from automated precipitation and streamflow gages are transmitted via <br /> <br />line-of-sight radio transmission. The brief transmission time required by <br />self-reporting gages (less than 250 milliseconds) allows for large data bases <br />to be acquired in substantial detail while eliminating radio interference from <br />other gages in the network. Where direct radio transmission to a base station <br /> <br />is not feasible, radio relsys are used. <br /> <br />B. Step 3 - Forecast the Flood <br />B.I. Manual Data Collection <br />A flood forecast procedure provides a means to translate rainfall that occurs <br /> <br />over the watershed to a stream elevation at a stream gage. Manual procedures <br /> <br />normally use tables, graphs, or charts that use average rainfall and a flood <br /> <br />index (input) to provide a flood prediction (output). Flood predictions vary <br />from a categorical forecast (i.e., minor, moderate, or severe flooding) to a <br />crest value. Figure 9 shows a typical flood forecasting procedure used in the <br />operation of a local flood warning system. <br /> <br />. <br /> <br />In a typical forecast procedure, the NWS gives the flash flood coordinator a <br />weekly flood index. This flood index is a measure of soil moisture. In <br />Figure 9, the flood index is the amount of rainfall in six hours required to <br />produce flood stage. The local coordinator uses the flood index to set the <br /> <br />32 <br />