FLOOD06271

• County: Otero
• County: Pueblo
• Community: Otero, Pueblo Counties
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Arkansas River Channel Capacity and Riparian Habitat Planning Study
• Date: 7/1/1999
• Prepared For: CWCB
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

I
I
I
I
I
I
I
I
I
I
I
I
I
I'
I
I
I
I
I

leaf area. Dense mature trees have large cross-sectional areas and can withstand relatively high
flows without breaking, therefore, provide the greatest resistance to flow (\1 ogel 1984).
Sparsely distributed trees can actually generate bank scour by accelerating flow around their
trunks.

Ftood attenuation. Flood discharge is strongly influenced by floodplain area. A larger
floodplain will have a lower peak stage than a smaller one for a given discharge. Additionally,
larger channel capacity allows a given flood event to pass more quickly.

Sediment toad. Riparian vegetation affects stream morphology by regulating sediment
supply and points of deposition. As stated previously, overbank vegetation influences sediment
transport by reducing flow velocities and causing deposition. Since the primary source of
sediment in many streams is bank erosion (Dunne and Leopold 1978), sediment load can be
significantly limited by bank vegetation. In agricultural watersheds with significant sediment
laden runoff, riparian vegetation traps sediments before they reach the stream (Lowrance et at.
1984).

Nutrient trapping and removat. Riparian vegetation traps both suspended and dissolved
materials and contributes significantly to the high fertility of floodplain soils. Suspended
particles in overbank flow and upland runoff are deposited when flow velocities are decreased
by vegetation. Most notably, carbon, nitrogen, and phosphorous concentrations in surface
water are effectively reduced by floodway vegetation (PeteIjohn and Correll 1984 ).
Additionally, riparian root systems uptake dissolved nutrients in subsurface water.

Wildtife habitat. Riparian habitats provide breeding sites, wintering areas, and
migratory stop-over areas for nurnerous wildlife species. The provision of food, cover, and
shelter has long been an important, widely recognized function of riparian vegetation (Brinson
et at. 1981, Minshall et at. 1989). This is especially true in the central and western United
States where riparian woodlands provide uncommon and structurally complex habitats relative
to the surrounding grassland or shrubland. Lowland riparian forests occupy only 3% of
Colorado's land area but contain the highest bird species richness and abundance than any other
ecosystem in the state except for marshes (Kingery 1998). The Arkansas River below John
Martin Dam harbors a nationally prominent white-tailed deer population (Ed Gorman, Habitat
Biologist, Colorado Division of Wildlife, October 1998,pers. comm.). Individual deer are
known to range throughout 350 to 400 acres of riparian woodland during the course of the year
(Kufeld and Bowden 1995). Riparian plant communities serve as travel corridors for local
populations of deer and other mammals, and as major migration routes for migratory birds.

Importance to aquatic systems. Bank vegetation also is an important component of
aquatic faunal habitat (Platts 1983). Streamside vegetation provides shade and cover for fishes
where it overhangs the water surface. The contribution of carbon to downstream aquatic
habitats is one of the most widely recognized functions of riparian vegetation (Brinson et at.
1981 ).

29