Flood Analysis
More than 7,000 stream gages nationwide provide streamflow data used to create hydrographs for water resource management and flood prediction. The map shows annual stream hydrographs from different U.S. cities.Copyright (left) U.S. Geological Survey; (right) NOAA, adapted from Satterlund and Adams (1992) http://ga.water.usgs.gov/edu/measureflow.html http://www.ncdc.noaa.gov/paleo/ctl/hydrograph2.html
Students learn how to use and graph real-world stream gage data to create event and annual hydrographs and calculate flood frequency statistics. Using an Excel spreadsheet of real-world event, annual and peak streamflow data, they manipulate the data (converting units, sorting, ranking, plotting), solve problems using equations, and calculate return periods and probabilities. Prompted by worksheet questions, they analyze the runoff data as engineers would. Students learn how hydrographs help engineers make decisions and recommendations to community stakeholders concerning water resources and flooding.
Water resource management and hydrology are specialized fields in civil engineering. Engineers analyze streamflow data for many purposes including flood prediction, water management and allocation, design and operation of locks and dams, and recreational safety and enjoyment. Hydrographs and flood frequency analyses are ways that engineers determine the probability that a certain area will flood during rainstorms of certain intensities, the expected response of a specific watershed region to a rainstorm, and annual/seasonal streamflow information.
After this activity, students should be able to:
- Plot an event hydrograph and make calculations using streamflow data.
- Use peak streamflow data to perform a flood frequency analysis for a particular region.
- Justify engineering decisions based on a region's annual streamflow.