Change in River Flood Magnitude

<div><div><i><strong>This data resource includes layers in a map service. To download it, please go to the "Layers" section of this page and click the name of the dataset. This will open a new page that features a download button.</strong></i></div><div><br></div><div><strong>Access the Indicator Materials:</strong></div><div>-<a target="_blank" rel="noopener noreferrer" href="https://d18lev1ok5leia.cloudfront.net/chesapeakeprogress/chart-assets/river-flood-frequency-in-the-chesapeake-bay-watershed-1965-2015/Analysis_and_Methods_Upstream_Flooding_07-31-2018.pdf">Analysis &amp; Methods</a></div><div>-<a target="_blank" rel="noopener noreferrer" href="https://d18lev1ok5leia.cloudfront.net/chesapeakeprogress/chart-assets/river-flood-frequency-in-the-chesapeake-bay-watershed-1965-2015/Data_Upstream_Flooding_07-31-2018.xlsx">Data File</a></div><div>-<a target="_blank" rel="noopener noreferrer" href="https://gis.chesapeakebay.net/ags/rest/services/ChesapeakeProgress/cpClimate_UpstreamFlooding/MapServer">Map Service</a></div></div><div></div><div>The Indicator’s flood magnitude and frequency estimates are based on stream gauge discharge measurements. Stream gauges continuously record water level, and U.S. Geological Survey staff measure discharge at each site every four to eight weeks to develop a stage-discharge relationship. That relationship is then used to calculate daily mean discharge, which is analyzed over time to estimate flood magnitude and frequency.</div><div></div><div><strong>Note: This Indicator supported progress tracking toward the Monitoring and Assessment Outcome in the original Chesapeake Bay Watershed Agreement, adopted in 2014. The Watershed Agreement and Adapting to Changing Environmental Conditions Outcome were revised in 2025.</strong></div>