FLOOD05149

• County: Delta
• Community: Delta
• Stream Name: Gunnison, Uncompahgre Rivers
• Basin: Gunnison
• Title: Cost Estimates for Removal of Debris, Bank Protection and River Training Along the Uncompahgre, Gunnison and the North Fork of the Gunnison Rivers
• Date: 1/1/1980
• Prepared For: Delta County
• Prepared By: Mt Highland Engineering
• Floodplain - Doc Type: Miscellaneous

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confidence. In 1985, for the major rivers in Delta County, all
information indicates that there is a very high risk that greater
than average flood damage will occur during next year's runoff, or
in the following years' runoff because of the extensive debris and
gravel bar deposits. At this time there is no way to predict the
certainty of next year's flooding damage 1 however, there are
several indicators that can bracket the probable range of damage
that could be caused by the runoff.

There are large amounts of very bulky debris in the river channel,
large trees and even a house. And the majority of the debris is
found upstream from all the bridges. Debris of this size affects
the hydraulics of the channel, especially at a narrow passage such
as a bridge, and particularly at a bridge with piers founded in
the main stream. Most of the bridges on the Gunnison, North Fork
of the Gunnison and Uncompahgre Rivers in Delta County have ceriter
piers. High, and even a normal runoff, will refloat the debris
and lodge the trees in the next bridge with a center pier.
Because there is so much debris, emergency crews will be busy
throughout the County cleaning out the debris clogged bridges
during the spring runoff. And, if there is insufficient emergency
personnel, the probability for flood damage will increase and so
will the costs. New channels cut by the previous flooding have
directed the flow of the river into unprotected banks adjacent to
farmland, bridges, roads and other structures. If they are
allowed t remain, the river will continue to cut into the banks
and eventually destroy the improvements.

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The third indicator of possible increased damage is the fact that
there is a better than even chance for higher than normal flooding
this coming Spring according to Derry Newby of the National
Weather Service. And, according to Mr. Newby, even a normal
snowpack can yield a high runoff under the right circumstances. A
high Spring flood could bring disastrous results by combining the
inevitable problems of high water with debris buildup on bridges
and loss of land and riparian improvements from bank cutting
through the channels left by last year's flood. Even an
inordinately low runoff will not solve the problem. There is
presently so much debris in the rivers that a low runoff this
Spring will not wash out the debris and the large trees will
remain in the channel for the next flood. 6lf

Based on these indicators and the present poor condition of th~ ~~'
river channels, estimates can be made of the range of probable 0" t.-
costs for a normal__()F_.h.~gJ:l,J:'l'!?.Qi!' if nothing is done to protect >ylt-"
public and private improvements. If there is a Spring runoff that
equals or exceeds last year's flood one can expect to see the
damages equal or exceed the damage recorded last year. This could
include the loss of State and/or County bridges, treatment plants,
farmground and other riparian improvements 1 a cost that exceeded
$1,600,000.00 in 1984.

A normal runoff will sweep the clogged channel of the large
and widen the new channels established by last year's flood.
increased debris, in the river will clog the bridges, damage the

trees
The

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