FLOOD03369 - Laserfiche WebLink

Home Browse Search

Rooky Ford: Although located well above the Arkansas River flood plain, on the south bank, Rocky Ford is typically subject to flooding from irrigation canals that intercept numerous small arroyos in the vicinity. The canals do not have by-pass structures so floodflows from the arroyos combine with irrigation flows to breach the canals. The overflow goes through Rocky Ford to pond in low-lying areas. During the April 29, 1999 flood the head gate of the canal on the Arkansas River was overwhelmed and allowed unrestricted inflow from the river. This caused the canal to fail and flooding in Rocky Ford. Dikes around sewage treatment lagoons were threatened, but never breached. On May 2, 1999 the town requested a loan of sandbags from the Corps. The same afternoon, approximately 7,500 sandbags were sent from John Martin Dam. Although recommendations were made for residents to evacuate, it was not an enforced evacuation. Most residents chose not to evacuate. Some homes experienced flooding of yards and basements. Sewer lines also backed up as a result of the flooding. La Junta: The local levees and Corps of Engineers constructed levee are only able to provide minimal protection for the unincorporated area known as North La Junta. North La Junta is subject to the highest risk for flooding due to its location within the relatively low southern overbank area of the Arkansas River. The Local Flood Protection Project Phase I General Design Memorandum study by the Corps in 1986 showed the entire North La Junta area to be within the 10-year floodplain. Aggradation of the riverbed in this reach compounds the problem. Since construction ofthe Corps of Engineers spoil bank levee in 1956, Otero County offIcials have estimated that channel capacity has been reduced down to a third from 15,000 c.f.s. to about 3,000 c.f.s. Residents claimed that areas unaffected by the major flood of 1921 and 1965 had flood waters reach them during the 1999 flood. In November 1997, the Colorado State Water Division 2 evaluated aggradation in the Arkansas River at La Junta between 1963 and 1997. They found that aggradation had occurred, but the corresponding loss in channel conveyance capacity was much more signifIcant. Some of this reduction was attributed to increased channel vegetation and debris. The State Water Division 2 evaluation indicated that the aggradation within the low point of the river channel ranged from 1.45 feet to 4.94 feet. The 1965 flood scoured the channel and briefly improved channel conveyance; however, the rate of aggradation appears to have increased dramatically in the years that follow. The increased base flow of Fountain Creek from the discharge of trans-mountain water from Colorado Springs may be a contributing factor to erosion within Fountain Creek and subsequent aggradation in the Arkansas River. These diversions from the western face of the Continental Divide started with the Hoosier Tunnel project in 1952 and increased with the completion of the Homestake Water Development Program by the cities of Aurora and Colorado Springs in 1965. The Fryingpan-Arkansas Project by the BuRec further increased this potential in June 1981; however, the City of Colorado Springs does not currently use its allotment of trans- mountain water from the BuRec project. The dramatic change in channel conveyance capacity is summarized in Table 3-3. Post Flood Assessment Report 20 Chapter 3 - Flood of April 29, 1999 Draft Revised 09/09/99