FLOOD11630 ‎(2)‎

• County: Statewide
• Basin: Arkansas
• Title: Post Flood Assessment Report - Arkansas River
• Date: 9/15/1999
• Floodplain - Doc Type: Flood Documentation Report

recorded on July 15, 1989. The Colorado Water Conservation Boarci estimated the 100-year
peak flow to be 1,643 c.f.s. and the 500-year peak flow to be 2,745 c.f.s. This gives some'
indication of the rarity of the event. Rainfall and flood conditions co~tinued in the area through
eazly August 1997. The flooding in Otero County occurred as a result of a number of smaller
storms over a period of a week. The heaviest rainfall was concentrated in the earfly part of
August 1997.
RECENT FLOOD CONTROL PROTECTION
Congressionally Authorized Corps of Engineers Proj~cts
John Martin Dam and Reservoir, completed in 1948, was the first improvement built by the
Corps of Engineers on the Arkansas River in Colorado. The dam spar,is the Arkansas River about
18 miles downstream of Las Animas and 58 miles upstream of the Kansas state lnie. It is a
concrete gravity overflow shvcture flanked by earth embankments. The reservoir extends 14
rniles up the valley and covers about 17,875 acres at maximum pool level. The reservoir storage
capacity at the maximum flood pool elevation of 3,870 feet is 605,115 acre-feet. "I'his is based
on the November 1994 storage-elevation curve, which was updated to account for estimated
sediment depletion. Of this capacity, 277,218 acre-feet is utilized for storage of irrigation water.
The water stored in the reservoir for irrigation purposes is released in accordance with the terms
of the Arkansas River Compact and at the request of the Compact Administration. In accordance
with the 1965 Flood Control Act, the Corps of Engineers is authorizecl to use, but not exceed,
10,000 acre-feet of the flood control storage space in John Martin Res~rvoir for a permanent pool
to enhance fish and wildlife resources and provide greater recreational opportuniti~s. The State
of Colorado is responsible for purchasing the water rights to establish and maintain the pool.
The permanent recreation pool has a minor effect on the flood control capability o.f the dam. The
maximurr~ operating pool elevation allowed including the permanent recreation pool is 3,851.87
feet; corresponding to a reservoir storage volume of 345,698 acre-feet. Currently under
agreement with the Arkansas Compact Administration between the St~ite of Colorado and
Kansas, the Corps of Engineers is only authorized storage of just under 9,000 acre••feet for
permanent recreational use. This equates to an elevation of 3,851.78 f~et and corresponds to a
reservoir storage volume of 344,654.
Other improvements constructed by the Corps of Engineers in the Arkansas River basin above
John Martin Dam include the Templeton Gap Floodway at Colorado Springs, the F'ueblo
Floodway Levee Extension at Pueblo, the Fountain Creek Levees and ~hannelization project
alsa at Puebla, and the Pinon Canyon Dam at Trinidad. P~11 aze single purpose flood cantrol
projects. The Templeton Gap Floodway was completed in 1948. It pr~tects an urban area in the
northeast sect~on of Colorado Springs from runoff that originates in a bowl-shaped drainage area
of about eight square miles and flows down the main channel of Templeton Gap. The floodway
intercepts and diverts the flow via a stabilized channel to Monument Creek, a tributary to
Fountain Creek. The Templeton Gap Floodway includes 8,713 feet of lined channel with a
capacity of 14,000 c.f.s. providing protection up to the 100-year flood.
Chapter 2- History of Flooding and Flood Protection
Post Flood Assessment Report~ 9 Dra~'t Revised ~9/09/99