Arkansas River Channel Capacity and Riparian Habitat Planning Study

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7 2 Animas that hreato Y g h tes, including cottonwood and salt- cedar, annually consumed p P approximately 15,000 acre-feet of water ( Bittenger and Stringham 1963:13 -15, 17 -21). The cottonwood trees in the valley were, however, in decline. ' While salt -cedar is used by wildlife many researchers report that salt -cedar has little food value and species diversity and density are lower than in the historic and preferred cottonwood - ' willow habitat; therefore, the dense salt -cedar stands: have lower wildlife values (Carpenter n.d.:6 -7). Vegetation studies attest to the changes inchannel morphology and to the spread of salt - cedar. Examples include studies on the spread of salt -cedar that indicate that "The oldest and most mature stands of salt -cedar were found near the Colorado- Kansas State line..." near where historic documentation first reports it (Lindauer and Ward 1968:3 -4, 24). Bittenger and Stringham (1963:13 -15) noted a significant increase In salt -cedar between 1936 and 1957 for the , reach of river between La Junta and Las Animas" which was during the drought years. Another example is the fact that the youngest cottonwoods near Bent's Old Fort are located near the present channel in areas that are suitable for seed germination while the oldest cottonwoods are ' located about 1,200 feet from the present channel in areas that were once active areas of the floodplain and were suitable for cottonwood seedling germination (Nadler 1978:90 -92). 1 concern in recent ears issthe slow disappearance Another biologics y of cottonwood from the valley and its importance in restoring habitat values (Snyder and Miller 1991; USACE 1999a:4042; Carpenter n.d.). Cottonwood loss is attributed to the reduction in flooding and declines in the amount of active channel that provided for suitable nursery sites (Lindauer 1970:11; Snyder and Miller 1991; Rood and Mahoney 1990; McDonald and Sidle 1992; Johnson 1994). There are also concerns for the effects of grazing or other utilization of floodplain areas by both livestock and wildlife such as deer and beaver, and for how grazing would affect cottonwood reintroduction/recovery efforts (Lindauor -76; Snyder and Miller 1991; Kufeld and Bowden 1995). The primary challenge to the recruitment of cottonwoods is the "attenuation of flooding [that] also prevents the essential geomorphic disturbance that creates new nursery sites" (Mahoney and Rood 1998:635). Cottonwoods are faced with increasing competition from other species such as the introduced kochia, Chinese elm, and Russian olive , (Lindauer 1970:73 -77). Significant floods, including the famous 1921 and 1965 Arkansas River floods that devastated Pueblo and downstream areas, are reported for the years 1904, 1908, 1935, 1937, 1942, 1944, 1947, 1955, 1966, 1997, 1999 (USACE1948:24; 1965:29 -30, 1970 :B17 -B23, D9- D12, 1973:48 -49, 1977a:9 -11, 1983a :4/54/8; 1999:5 -9, 13 -15; Lindauer and Ward 1968:3). In the study area, the 1999 spring flood inundated major portions of North La Junta and portions of La Junta and overtopped and damaged the North La Junta levee as well as the Las Animas levee. ' Significant damages also occurred along Fountain Creek near towns and cities such as Manitou Springs, Colorado Springs, Fountain, and Pueblo ( USACE 1999b, 1999c, 1999e). Flood events are known to add and distribute. significant amounts of sediments to the river's channel and adjacent overbank areas. In the study area, the primary tributaries to the Arkansas River that are contributing substantial amounts of sediment include Timpas Creek, Horse Creek, Adobe Creek, and the Purgatoire'River. "With the reduction in inflow and the ' increase in phreatophytes at the head of the [John Martin] reservoir, there has been a decrease in 20 ' 1