DISTINGUISHED CAREER AWARD: GO WITH THE FLOW

Accurate measures of stream discharge are the underpinning of computations of sediment and chemical loading, magnitude and frequency of flooding, and channel and floodplain change. The greater the discharge, the more difficult and uncertain discharge magnitude becomes. Thirty floods determine the envelope curve of maximum floods documented in the United States by the U.S. Geological Survey. The reliability of computed discharge of these extraordinary floods was reviewed and evaluated using current best practices. This resulted in 5 of the 30 floods having revised peak discharges greater than about 10 percent different from the original published values. Errors identified in the reviews include misidentified flow processes, incorrect drainage areas, incorrect latitude and longitude, improper field methods, arithmetic mistakes in hand calculations, omission of measured high flows when developing rating curves, and typographical errors. Common problems include two-section slope-area measurements, poor site selection, uncertainties in Manning’s n-values, inadequate review, lost data files, and inadequate high-water marks. Highly unsteady flow and resulting transient hydraulic phenomena, two-dimensional flow patterns, debris flows at streamgaging stations, and the possibility of disconnected flow surfaces are examples of unresolved problems not well handled by current streamflow methodology. In recent years significant progress has been made in instrumentation for making direct discharge measurements, but very little has been accomplished in advancing methods to improve indirect discharge measurements. Non-contact methods such as ground-penetrating radar to measure channel area and pulsed Doppler radar to measure surface velocity hold significant promise. Results of continuous non-contact flow measurements over a 4 month period and one significant flood hydrograph compare well with data from a streamgaging station at the same site.