Title

Retrospective Case Study of the Impact of Rain Gage Network Reductions on National Weather Service River Forecasts in the Susquehanna River Basin

Item Type

Presentation

Location

Elaine Langone Center, Terrace Room

Session

Watershed Hydrology and River Hydraulics, moderator Jessica T. Newlin

Start Date

22-11-2014 1:00 PM

End Date

22-11-2014 2:15 PM

Description

Funding cuts in 2013 resulted in the loss of 63 United States Geological Survey rain gages in the Susquehanna River basin. For this study, the impact of gage reductions on gage network density and on calculations of Mean Areal Precipitation (MAP) for the sub-basins used for Middle Atlantic River Forecast Center modeling and forecasting is examined. In addition, to further examine the impacts on operational river forecasts, sets of retrospective hydrologic forecast model simulations are made with and without the removed gages for several significant flood events that occurred prior to the loss of these gages. The loss of gages leads to an increase in MAP uncertainty during high impact events. While changes in river crest flows are small most of the time, in about 10% of the cases the crest flow accuracy was degraded by more than 20%. In a few cases, this increased forecast error and/or uncertainty could make it more difficult to make timely river flood warning and evacuation decisions. The study demonstrates the value of retrospective simulations and flood crest analyses in quantifying the potential impacts of gauge network reductions on river forecast accuracy.

Language

eng

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Nov 22nd, 1:00 PM Nov 22nd, 2:15 PM

Retrospective Case Study of the Impact of Rain Gage Network Reductions on National Weather Service River Forecasts in the Susquehanna River Basin

Elaine Langone Center, Terrace Room

Funding cuts in 2013 resulted in the loss of 63 United States Geological Survey rain gages in the Susquehanna River basin. For this study, the impact of gage reductions on gage network density and on calculations of Mean Areal Precipitation (MAP) for the sub-basins used for Middle Atlantic River Forecast Center modeling and forecasting is examined. In addition, to further examine the impacts on operational river forecasts, sets of retrospective hydrologic forecast model simulations are made with and without the removed gages for several significant flood events that occurred prior to the loss of these gages. The loss of gages leads to an increase in MAP uncertainty during high impact events. While changes in river crest flows are small most of the time, in about 10% of the cases the crest flow accuracy was degraded by more than 20%. In a few cases, this increased forecast error and/or uncertainty could make it more difficult to make timely river flood warning and evacuation decisions. The study demonstrates the value of retrospective simulations and flood crest analyses in quantifying the potential impacts of gauge network reductions on river forecast accuracy.