The 500 Year Floods
This Earthcache will take you to TaHaZouka Park and along the paved Cowboy Trail to one of the areas where the Elkhorn River is prone to flooding. Please park at the parking coordinates provided. The Cowboy Trail Head is there and will guide you through the floodplain to GZ. A floodplain is a wide, flat, low-lying area of land on both sides of a river channel. Floodplains are formed over thousands of years by the gradual flooding and draining of a river. Each time a river floods (from heavy rainfall, snow melt, or melting glaciers for example), the silt and sand it carries is deposited on the sides of its banks, eventually building up a flat layers of alluvium.
The most recent flood occurred on June 15, 2010, where Norfolk, NE saw devastating flooding from the Elkhorn River that not only puts it in the 100 year flood category, meaning a flood like this would only occur once in a hundred years, but also falls into the 100-500 year flood category. According to FEMA (Federal Emergency Management Agency), the flow rate for the Elkhorn River in the Norfolk area for a 100 year flood would be 30,000 cubic feet per second. On Tuesday, June 15 at 9:00 pm, the flow rate was 38,800 cubic feet per second, putting it in the 100-500 year flood category.
Flood stage, the level at which overflow of the natural banks of the river begins, for the Elkhorn River is 12 feet. The river crested, or hit a high of 16.85 feet. This led to the extreme flooding that put south Norfolk under water, caused the evacuation of houses, threatened numerous business, closed several roads & major highways, and caused the nearby railroad bridge to collapse -- killing railroad worker Jeff Scholl. The effects and damage caused by these floods will be visible for many years to come.
To log this Earthcache, complete the following tasks:
1. (Optional) Post a picture of you or your group holding your GPSr at GZ with the river in the background.
2. Give examples of flood damage still present at GZ and the area around you.
3. Estimate the current width of the river at GZ.
4. According to your GPSr, what is the elevation at GZ?
5. Walk as close to the edge of the bank as you are comfortable. Describe the current condition and consistency of the river. Are any sandbars present?
6. Across the river, there are areas of the bank that have been freshly cut away. Looking at this, how can you tell that there have been many more floods in the past?
Post only the optional picture in your log and submit the answers through our profile link. Be sure to note which Earthcache your answers belong. Any log that has answers posted will be deleted. Any log for which we have not received answers within a reasonable amount of time, will also be deleted.
Have fun and enjoy!
Congrats on FTF to: Bobcam on 9-4-2010
References:
"Norfolk Daily News" & www.norfolkdailynews.com
"Norfolk Insider"
www.scienceray.com
Nebraska Department of Natural Resources website www.dnr.state.ne.us
Placed by a Nebraskache Member