University of Colorado
Department of Civil, Environmental and Architectural Engineering
Preliminary Exam – June 2004
											
Clearly describe the steps and all the assumptions you make. I am keen on these than on the “correct numerical answer”. You may consult book(s), notes, internet – but refer to the source in your answers.

1. Folsom dam, on the American River, near Sacramento, was designed around 1940. The main purposes of the dam were flood control and water supply. At that time the reservoir was designed to protect the adjoining communities against a 100-year flood. 
(i) Is the dam serving it’s function of flood control now (ie. In  the Post-1940 period)?
(ii) If not what is the change in the 100-year flood between the pre and post-1940 periods?
(iii) What might be the cause for the nonstationarity (i.e. change in the 100-year flood)?

There are several methods to calculate the 100-year flood choose the method you think is the best (and give a reason).
You can obtain the monthly and annual peak data for the American River at Fair Oaks gauge (which is a fairly representative gauge) from the USGS website http://water.usgs.gov/

(iv) If you were to design the Folsom dam now, for water supply, what would be the size of the reservoir?  You can assume a reasonable per capita water consumption per day and assume the population of service to be around 150,000. 
[hint: develop the storage-yield curve]

2. Fort Collins experienced a series of severe storms on July 28, 1997 that resulted in one of the worst flooding. Below is one of the storms in the series – if this storm occurred over Boulder, what will be the total volume of runoff

Time (hours) 		0		1 	2 	3 	4 	5 	6	7
Precipitation (mm) 	0		1.27	20.1	22.9	33.3	55.1	13.7	0
Assume sandy loam soil with 75% initial effective saturation.
Obtain necessary information (e.g., area of Boulder etc. from on-line sources)

If you have to obtain the runoff hydrograph from this storm what would you do?
(Assuming that you can obtain the physical characteristics of the basin from DEMs)
You may actually compute the hydrograph or describe in detail the steps.