Lab 08 Environ-Villa Nova Park

GEOL 305, Lab #8 Villa Nova Park Flooding Exercise You will use the US Geological Survey (USGS) annual peakflow data for the Villa Nova Park gaging station on the Gwynns Falls to construct a rating curve, calculate flood recurrence intervals, get more experience with importing and analyzing data in Excel, and explore how different statistical models affect ‘predictions’ or future scenarios. Downloading data 1. To obtain data, please navigate to http://nwis.waterdata.usgs.gov/md/nwis/uv/?site_no=01589300&agency_cd=USGS 2. Use the dropdown menu under ‘Data Inventory’ to choose ‘Peak Streamflow’. 3. The website is currently being revised, so it’s a bit funky. To download the data, first choose ‘Reselect output format’ under Output Format. When the page reloads, select ‘Tab-separated data’ without changing any other fields, then hit ‘Submit’. Download and open with Excel. Once you have the data, do the following 1) Plot a rating curve of stage ( y-axis ) versus discharge ( x-axis ) using the USGS data. For this and all plots, be sure to include axis labels. (5 pts) 2) Fit trend lines to the rating curve data using (a) linear and (b) a second fit (power law, exponential, or logarithmic) models, using whichever fits better for (b) as indicated by higher R 2 values. Report the equations for the model fits, including the R 2 values, in a table. (2 pts) 3) Rank the discharge events from largest to smallest. Then calculate the recurrence interval and the exceedance probability for the peak discharge in each year. These results should be reported in a table inserted in the lab. (10 pts) 4) Next, plot the discharge ( y-axis ) versus recurrence interval ( x-axis ) and fit that relationship with both linear and a second fit (power law, exponential, or logarithmic) models. Report the equations for the model fits, including the R 2 values, in a table. (5 pts) 5) Calculate and report the probabilities of the following floods occurring in a given year: 1500 ft 3 s –1 and 5000 ft 3 s –1 . (2 pts) 6) Use the rating curve, recurrence interval, and exceedance probability models to estimate the discharge and stage for floods with 2-year, 10-year, 25-year, and 50-year recurrence intervals. Do so for both the (a) linear and (b) power law (or exponential) models. 7) Calculate the percent differences (1) between the actual discharge data and each of your recurrence models and (2) between the recurrence models. Please briefly discuss which model works better for (1) discharge versus recurrence interval and (2) stage versus discharge. (12 pts) 8) Extrapolate to get an estimate of the discharge and stage for 100-year and 500-year flooding events. Again, compare results between the linear and power law models, including calculating the percent difference between the models. (3 pts) 9) Navigate to the USGS StreamStats website: https://streamstats.usgs.gov/ss/ . 1. Input the USGS gage number (01589300) for Gwynns Falls at Villa Nova Park, MD. 2. Select Maryland and District of Columbia ; once you have done so, you should see blue streamlines (river channels) appear.