New York’s Expanded USGS StreamStats Tool

The U.S. Geological Survey (USGS) has developed a web-based application that operates in conjunction with the existing StreamStats application for New York State to incorporate projected precipitation changes under various 21st century climate change scenarios. This application will allow transportation planners and engineers to explore how climate change may affect high flows, which can assist with the design of over-water infrastructure (such as culverts and bridges) to accommodate these changes.

The application uses regression equations that were developed by USGS and are implemented in StreamStats. These regressions use variables based on topography and land cover combined with either annual precipitation or stream runoff to predict flood peaks of various magnitudes across six regions in New York State. These regressions can be used to estimate flood magnitudes for basins throughout New York that do not have stream gages. The climate change application uses climate model output and greenhouse gas trajectories over various periods in the 21st century to make estimates of how predicted changes in precipitation and resulting runoff may affect flood peaks.  The resulting expected changes in future flood peaks can help inform a variety of planning and design decisions, including the engineering of roads, culverts, and bridges.

Culverts and bridges represent a significant portion of New York’s transportation infrastructure, which includes over 12,000 state, county, and local over-water bridges, and almost 100,000 culverts in the state network of roads alone. The New York State Department of Transportation (NYSDOT) uses StreamStats to determine peak flows on streams where they intersect with roadways, to determine the amount of water that the engineering design of these assets must be able to accommodate. For bridges and large culverts, NYSDOT is concerned primarily with the anticipated flood discharge levels for 50- and 100-year flood events. As climate change is projected to cause more frequent extreme weather events and heavy precipitation, the peak flows for 50- and 100-year flood events will likely increase, and the addition of the climate change application to the tool will help predict these changes. Transportation planners and engineers in New York will be able to use this information to qualitatively assess how to modify the design of particular assets to ensure that they perform adequately over their lifetimes in light of more severe flooding conditions.

For the tool, USGS and NYSDOT selected five climate models[1] that best resembled New York’s historical precipitation patterns. The models are calibrated for two different IPCC emissions scenarios: a moderate emissions scenario (Representative Concentration Pathway 4.5, or RCP 4.5) and a high/increasing emissions scenario (RCP 8.5)[2]. These scenarios are consistent with those used by other state agencies in New York and in the state’s updated report, “Responding to Climate Change in New York State” (ClimAID 2014). The climate models were downscaled to 800-meter grids for use in the application, and the tool now estimates streamflow statistics under future precipitation conditions for three different time periods: 2025-2049, 2050-2074, and 2075-2099.

Engineers designing culverts, roads, and bridges in New York, as well as other planners and water resource managers, will be able to use the tool for qualitative analysis of the impact of future precipitation patterns on streamflow. The online GIS-based tool is used by selecting a location along a stream on the map; the tool delineates the watershed based on topographical features of the basin (such as stream slope, drainage area, and percentage of forested area) and mean annual precipitation. The tool then calculates how these physical features impact streamflow, producing a variety of statistics for flood discharges for different probabilities of rainfall events ranging from 1.25-year to 500-year events. For designing transportation assets with longer design lives, such as large culverts, NYSDOT primarily uses the statistics for some of the less frequent but more severe events (50-year and 100-year). The incorporation of climate models into this new tool will help improve the value of these statistics given changing climate conditions.

StreamStats is a state-specific tool developed by USGS according to agreements with each participating state. In general, data is input into each state’s tool from stream gages, which directly measure streamflow at specific locations along the stream. Users can access these data through the tool without having to visit the gaged sites, but can also use the tool to obtain information about the basin and to compute estimated peak flows for different flood events along the gaged streams. Some states, including New York, have sufficient data and information about the stream network and topography to estimate flow statistics even on ungaged streams (those without data collection sites). New York’s expanded tool with the climate change application will therefore allow users to qualitatively assess how these statistics are affected by climate change on both gaged and ungaged streams.

New York is the first state to develop a tool that will incorporate climate change projections. This expansion of the state’s StreamStats tool was funded by the Federal Highway Administration through the NYSDOT climate resilience pilot project for the Lake Champlain Basin, which is focusing on methods to improve design and planning of culverts in light of climate change impacts. The project began in early 2014; version 1.0 of the climate change application became available online in fall 2015, along with an accompanying report.

 

This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on June 28, 2016.

 

[1] The climate models were selected from CMIP5, or the Coupled Model Intercomparison Project Phase 5, which is an effort of the World Climate Research Program to promote a standard set of climate change model simulations for evaluation and comparison. For more information on CMIP5, see http://cmip-pcmdi.llnl.gov/cmip5/.

[2] The emissions scenarios (RCPs) used for the tool have been developed by the international research community and used for the IPCC 5th Assessment Report (AR5). The scenarios produce different climate projections based on different socioeconomic, technological, and biophysical assumptions made about human activity in the future. For a description of RCPs, see Intergovernmental Panel on Climate Change, Scenario Process for AR5, Representative Concentration Pathways: http://sedac.ipcc-data.org/ddc/ar5_scenario_process/RCPs.html.

 

Publication Date: December 2015

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  • Climate science
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