Department of Geosciences
North Dakota State University

Geology 300:
Flood Frequency Exercise

(Portion of a Landsat Thematic Mapper (TM) image of part of the Missouri River Floodplain near Glasgow, Missouri. For the original and other images, see http://edcwww2.cr.usgs.gov/moberly.html.
NDSU According to Dr. Laurence C. Smith, UCLA Department of Geography, "a volcanically-triggered glacial outburst flood or jökulhlaup occurred on the Skeidararsandur, Iceland November 5, 1996, the largest ever recorded in Iceland (at peak flow the discharge rivaled that of the Congo, the worlds second largest river, and was comparable with that estimated for the late Quaternary outburst flood from Glacial Lake Missoula). The flood eroded and deposited up to 9.1 m of sediment, removed major stretches of the most important highway in Iceland, destroyed two bridges, and caused damage estimated at U.S. $15,000,000. The total volume of water released from the glacier is estimated at 3.5 km3, and was the most rapid jškulhlaup recorded for the area. This site is still rapidly adjusting to the extreme erosional and depositional changes caused by this extreme event. For general information and great photographs of this event, see the May 1997 issue of National Geographic (vol. 191, no. 5)". (info from http://lena.sscnet.ucla.edu/iceland.html).

NDSU Exercise on River Flood Frequency

[See the publication: Saini-Eidukat, B. (1998) A WWW and spreadsheet based exercise in river flood frequency analysis. Journal of Geoscience Education, v. 46, pp. 154-156.]

Find historical Peak Flow Data on a river of your choice (Excluding the Red River at Fargo), using the U.S.G.S. National Water Information System (NWIS).

Be sure that the river you choose has Peak Flow Data available for a time period of over 40 years.

Here are the steps to take:

After creating and printing your chart, answer the following questions:
1. Draw a straight line (best-fit, not dot-to-dot) through the data points.
2. What is the discharge for a 100 year flood? A 20-year flood?
3. What is the recurrence interval for a flood with median discharge for your river?
4. What is the average annual flood (i.e., the arithmetic mean of maximum annual discharge for length of record?

You may work together with a partner, but each partner should hand in an analysis of a different river. Print out your raw data file, and include the river name and gaging station number.

NDSU Home | Geosciences Home | Instructional Web Sites | Environmental Geology Home Page | Geology in North Dakota |

B. Saini-Eidukat
Environmental Geology
Geology 300