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River Forecasting Case Study This module takes the learner through the considerations for the river forecasting decisions associated with the remnants of Hurricane Ivan on 17-19 September, 2004 for the Susquehanna River system in Pennsylvania and New York. The module assists the learner with applying the concepts covered in the foundation topics of the Basic Hydrologic Sciences course. Some of the specific topics pertinent to this case are soil conditions, the impact of QPF on runoff, runoff models, runoff processes, routed flow and stage-discharge relationships. Observations of upstream conditions and comparisons to historic crests are also examined to assist with operational flood forecast decisions. The core foundation topics are recommended as a prerequisite since this module assumes some pre-existing knowledge of hydrologic principles.

1. Describe hydrologic conditions in the Susquehanna River basin preceding the events associated with the remnants of Hurricane Ivan in the Susquehanna River Basin on the 17-19 September 2004. a. Describe the local geography and its impact on storm runoff b. Use climatology as a reference for potential storm impacts c. Describe soil texture, soil profile, and ground cover conditions for the region d. Analyze antecedent soil moisture levels for the area 2. Analyze the observed and forecast rainfall, current factors influencing runoff, and the initial river forecasts for the Susquehanna River preceding this event. a. Analyze rainfall and soil information and anticipate the impact on runoff b. Interpret runoff information from river models c. Anticipate how errors in the QPF may impact the magnitude of runoff 3. Apply knowledge of runoff processes and river modeling to observed and historic streamflows to develop a forecast for the Susquehanna River at Wilkes-Barre for this event. a. Analyze and anticipate dominant runoff mechanisms during a developing flood event b. Examine the relative contributions from different components of the forecast hydrograph c. Examine how changes in precipitation can influence the expected crest d. Analyze how precipitation forecast errors impact runoff forecast errors e. Anticipate the impact of runoff that is routed from upstream areas f. Use observations and historic information to assess the likelihood of the predicted extreme event g. Interpret and adjust guidance from river forecasting models h. Issue a river forecast despite uncertainties i. Appreciate how forecaster experience can play a very important role in the forecast process. 4. Assess lessons learned during the forecast process leading up to and during this flood event. a. Validate how the river forecast model did for the peak stage b. Interpret how the different components of the river model contributed to the forecast and its errors c. Explain the important role of accurate stage-discharge relationships d. Relate this event to previous major flood events
hydrology, hydrologic cycle, runoff, runoff processes, rainfall runoff, soil moisture, soil moisture anomaly, infiltration, percolation, baseflow, quick response runoff, infiltration rate, infiltration capacity, infiltration excess overland flow, saturation excess overland flow, depth-to-bedrock, pre-event water, hydrograph, flood prediction, flood prediction process, surface runoff, precipitation, snowmelt, subsurface runoff, interflow, soil properties, basin characteristics, urbanization, runoff volume, runoff timing, channel slope, soil texture classification, soil composition, soil profile, surface properties, simple runoff modeling methods, soil characteristics, runoff modeling, Hurricane Ivan, Susquehanna River, Susquehanna River Basin, Wilkes-Barre, Elmira, Vestal, Meshoppen, Hurricane Agnes, Hurricane Frances, QPF, Quantitative Precipitation Forecasting, Chemung River, North Branch Susquehanna, West Branch Susquehanna, Juniata River, Mainstem, clay, slit, sand, loam, radar-derived rainfall, FFG, Flash Flood Guidance, basin-averaged rainfall, basin-averaged runoff, runoff ratio, routed flow, local runoff, crest, peak stage, stage, flood stage, flood of record, flow, discharge, rising limb, receding limb, unit hydrograph, AHPS, River Forecast Center, stage-discharge relationship, rating curve, Lag and K method, USGS
July 2014: Since the module's publication in 2007 there have been changes in the tools and models used within the NOAA River Forecast Centers. The material and exercises may be less relevant than they were at the time of publication.




