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Hydrology of Inland Flooding. Stream Gauges Hydrologic Forecast Process Forecast Considerations Forecast Hydrographs. 3-1. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges. Stream Gauges.
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Hydrology of Inland Flooding • Stream Gauges • Hydrologic Forecast Process • Forecast Considerations • Forecast Hydrographs 3-1
Stream Gauges • Manual gages (wire weight or staff) • Low cost • By definition, requires trained human observer • Not usually available at night • Automated gages • Installation costs + Maintenance costs • Available 24/7
Hydrologic Forecast Process • Modeling how much rain gets into the river (Rainfall to Runoff) • Modeling how fast water gets to the river gage (Unit Hydrograph) • Modeling how fast upstream water arrives at the gage (Routing) • Translating water volume into water height (Rating)
Rainfall to Runoff Modeling Rain DIRECT SURFACE INTERFLOW BASEFLOW 6 hours 12 hours 18 hours 24 hours 30 hours T=0 hours
Routing Gage Height Time
River Forecasts – How are they created? Upstream Flow Upstream River Gage Observed Precipitation Future Precipitation Local Basin Soil Model Rainfall to Runoff Unit Hydrograph Runoff to Flow Forecast River Gage Basin Local Flow Total Flow (cfs) Rating Curve Flow to Stage Forecaster Modification Forecast To Public
Forecast Considerations • Ground State (How dry is it?) • Past Model Performances • Rainfall (Gage-based or Radar-based?) • Rainfall Variability • Space • Time
Forecast Hydrographs • Model Hydrographs • Forecast Hydrographs
Summary Which river gauge requires a stilling well? A. Acoustic sonar B. Float type C. Pressure transducer
Summary What type of runoff causes the river to rise the quickest? A. Direct runoff B. Interflow C. Baseflow
Summary What hydrologic method takes basin-wide runoff and converts it to flow (discharge) over a period of time at the river gauge? A. Rainfall to Runoff model B. Unit Hydrograph C. Routing model D. Rating curve