New England WSC seminar series Benthem 20181026

Date/Time: Friday, October 26, 2018, 12:00 pm 
 

Title: Assessing geomorphic change from increasing flood frequency using stream gage data

Presented by: Adam Benthem and Katie Skalak, Earth Systems Process Division, Hydrodynamics Branch

Location: USGS, Massachusetts Office, Northborough, MA

Abstract: 

USGS’s extensive stream gage network has greatly advanced our hydrologic understanding of watersheddynamics through the calculation of long-term streamflow measurements. Discharge, however, is not a direct measurement but rather derived from measurements of channel area, water height, and velocity. These underlying direct measurements are useful in their own right and can be valuable for understanding physical processes linked to stream flow. Understanding channel morphology can provide insight into the physical processes operating in rivers which affect bank stability, flooding, and sediment transport. The USGS regularly collects channel cross section data at stream gages to correct for changes in channel geometry and to produce accurate rating curves. These measurements are performed several times a year at all stream gages, providing a long-term dataset of changes in river form. We are compiling river gage channel data located on alluvial streams in the Northeast and quantifying the difference in variability in channel area between pre-1975 and post-1975 data. Results are examined for spatial trends as well as compared to shifts in the hydrograph record. Using historical aerial images, we assess whether these gage measurements are representative of local channel shifts, by comparingchanges in river capacity to shifts in channel width at 11 locations.