Recurrence interval homework

0. This assignment will use data from the USGS stream gauges that are located on the Maury River up- and downstream of Lexington. You should have already been to the stream gauge sites for the Maury River at Buena Vista and Rockbridge Baths but before, you were accessing current conditions- this time you will be looking at historical data. To do this, go to "Summary of all data for this site" for BV or Rockbridge Baths (it does not matter which you do first) and select ""Peak streamflow". This will give you the highest discharge measurement collected during each of the years that the gauge has been operational. Request the date in table format and copy and paste it into an excel spreadsheet.

1. How far apart are these two stream gauges as the crow flies?

2. Sort your data according to discharge (the the highest discharge year at the top). What are the five years with the highest discharge events?

3. In how many years has the rivers at either of these stream gauges been at flood stage (using the NWS definition)?

4. How many years of record are available for each of the stream gauges?

5. Assign a rank and calculate a recurrence interval for the peak discharge event for each year.

6. Plot discharge (y axis) as a function of recurrence interval (x axis) on a scatter plot with a logarithmic scale on the x axis. Format a logarithmic trend-line through two or three portions of the data so that you get a visually good fit (you will not be able to do this with only one trend for all of the data).

7. Select "display equation on chart" or use the linest function to find the relationship between the recurrence interval and the discharge for all or your trend-lines.

8. Use these equations to calculate the discharge for 10- 50- and 100-year floods for both gauges.

9. How many times larger is the dishcarge for a 10-year event at RBB than for your observed discharge at Jordans Point Park this week?

10. Given the nature of the observations available to you, comment one your ability to effectively characterize the discharge for10-, 50-, and 100- year flooding events in our area?

Send me an email with a .doc(x) file with the following:

1. distance between stream gauges

2. top five years (in order) for BV and RBB... Question:

3. numbers of years with "floods" BV and RBB

4. years of record for BV and RBB

6. ...plots for both gauges...

7. ...equations with ranges of appropriate recurrence interval for both gauges

8. 10- 50- and 100-year floods for both gauges

9.  Xtimes...

10. brief (but effective) answer...

by the beginning of class on Wednesday.