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

Problem Area

Annual Yield (ton)

Mean Daily Load (tons/day)

11
15
83'
175
130

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Table 3.3, Existin

3 4,100
4 5,600
5 30,200'
6 63,800
7 47,500
. Average of above and below diversion values,

causes scour and deposition and inhibits effective convey ce of water and sediment. Third,
the sediment transport potentials along the river area are erra ~ as welL Even with the
approximate methods used in this study, more unifo11J1ity and clearer trends would have been
expected,

The channel appears to be largely impacted by three phenomena: a reduction in peak
flows due to the upstream reservoir, changes in the vegetal makeup of the floodplain, and
agricultural encroachment. The reduced peak flows cause the channel to become smaller, This
shrinkage is often exhibited as narrowing, Vegetation moves into the newly formed bank and
inhibits its widening again during high flows, LikeWise agriculture moves closer in and
functions in essentially the same manner, Reduced peaks induce the sense that the river needs
less room. In much the same way this encroachment inhibits reWidening of the channel.
Additionally, leveeing further restricts the flow pathiand causes incision and bank instability,
The battles are fought, sometimes at considerable cost, and the river responds With further
instability. The cycle continues and the effective capacity becomes less and less,

Groundwater/Surface Water Interaction

..

Over the course of the study, many landowners indicated that surface water flooding
from the Arkansas River was a secondary problem compared to saturation from groundwater,
While groundwater/river flow interaction is outside the scope of this study, some qualitative
discussion is offered here because of its relevance to recent events and the operation of John
Martin Dam,

Groundwater/surface water interaction is a natural, dynamic process influenced by
many variables which change over time, The simplest way to illustrate gross interaction is to
consider the relative elevations of both the groundwater and river water levels at a given point
in time. If the two water level elevations are the sanj.e, they will remain this way, If the river
level is lower than the nearby groundwater level, they will attempt to equalize through transfer
from groundwater to river. Conversely, if the river level is higher, the transfer occurs in the
opposite direction, and this is the case that will be discussed further.

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