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The Suncook River at Main Street in Suncook, New Hampshire, in the flood of May 2006. USGS.
The U.S. Geological Survey has long worked with the Federal Highway Administration (FHWA) and state transportation agencies on water issues affecting roads and bridges. In New England it is improving flood-flow estimates, defining channels at bankfull flow, documenting storm tides from coastal storms, and studying flood frequency, extreme inland floods, rock blasting effects on groundwater, and road salt in runoff.
Five focus areas
The USGS New England Water Science Center identified five areas for new work with the FHWA and the transportation departments of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont:
| Area | Goals |
|---|---|
| Streamgaging networks | more gages on small, urban and steep watersheds; recording gages in place of crest-stage gages; gages at critical infrastructure |
| Flow frequencies and statistics | regularly updated peak-flow equations; effects of roads on stormwater; culvert slopes and velocities for fish passage |
| Water quality | acute and chronic levels of road runoff constituents and their share of total maximum daily loads; chloride and sodium in snowmelt; the SELDM runoff model |
| Bridge scour and sediment | regional scour-risk equations; monitoring bridges at risk; streambed movement in high flow |
| Hydrologic and hydraulic modeling | lidar flood-inundation maps; two-dimensional models of flow around structures; ice-jam tools; better friction calibration |
Recent work
Flood and flow statistics
Equations now estimate flows from 50- to 0.2-percent annual exceedance probability — the 2- to 500-year floods — across New England, kept current by new streamgage data.
- Maine (with MEDOT): monthly and annual mean flows and flows from 99- to 1-percent AEPs, using only recent data (report); and 100- to 0.2-percent flows for small, ungaged streams (report).
- New Hampshire (NHDOT): 50- to 0.2-percent flood flows at gages and equations for ungaged streams (report).
- Rhode Island (FEMA): 20- to 0.2-percent flood flows (report).
- Massachusetts (MassDOT): improving 20- to 0.2-percent estimates.
- Vermont (FEMA): 50- to 0.2-percent flood flows (report).
- StreamStats, a web tool that delineates a basin and estimates flow statistics for any ungaged site, was implemented for Maine with MEDOT (fact sheet).
Water quality
Runoff from roads, parking lots and construction carries sediment, nutrients, metals and deicers, a concern where it feeds impaired waters or water supplies.
- Massachusetts highways (FHWA, MassDOT): 13 monitoring stations in 4 ecoregions, 2005–2007, 1,523 runoff events (report).
- Bridge decks (MassDOT): phosphorus and suspended sediment from bridges in eastern Massachusetts over 2 years.
- Rock blasting (NHDOT): traced nitrate in groundwater near roadway blasting to its sources and mitigation (paper).
- Interstate 95, Connecticut (FHWA, CTDOT): road-deicer effects upstream and downstream of I–95 in four small watersheds, 2008–2011 (report).
- Vermont state highways (VTrans): chloride above and below highway bridges in three Chittenden County watersheds, 2005–2008 (report).
- SELDM (FHWA): the Stochastic Empirical Loading and Dilution Model uses Monte Carlo methods to estimate highway-runoff concentrations and loads, their effects on receiving waters, and how well best management practices might work (manual).
Flooding along the Woonasquatucket River in Providence, Rhode Island, March–April 2010. USGS.
Bridge scour and flood modeling
- Bridge scour: techniques to measure and quantify scour through the National Bridge Scour Program (reports).
- Cold River and Warren Brook, New Hampshire (NHDOT): flood elevations to guide rebuilding after the flood of October 8–9, 2005 and to update flood maps (report).
Sources
Based on Transportation and Hydrology Studies of the U.S. Geological Survey in New England, USGS Fact Sheet 2016–3009, New England Water Science Center, U.S. Geological Survey (DOI); a work of the United States government in the public domain. The photographs come from the fact sheet's PDF.
Licence : CC0 1.0 (domaine public) · Adapté de pubs.usgs.gov
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