FLOOD01153

• County: Montezuma
• Community: Dolores
• Stream Name: Upper Dolores River
• Title: An Evaluation of the Dolores River at Dolores
• Date: 9/1/1992
• Prepared For: Dolores
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

Dolores River

for the right bank. Nonetheless, it: would be advisable to
include this area J.n any future de1:ailed analyses if the
landownl~rs can be convinced of their vulnerability to flooding.

The main existing levee extends from just upstream of
Highway 145 to the 4th street bridqe (cross sections 2 to 11.1,
Attachm.mt 7). It is heavily armored with riprap but lacks about
1 foot <)1' freeboard at the downstrl~am end to comply with FEMA's
minimum criteria (Appendix D) of 4 feet of freeboard adjacent to
bridges and 3 feet elsewhere. Upstream of the 4th street bridge,
the exil;ting ground needs to be raised an average of just, over
4 feet. Near 5th street a short floodwall section (about
100 fee': long and 3 feet high) would be included to prevent the
taking .)1' two structures which are close to the river. The new
levee w.)uld then continue for about 150 feet up to the next
existinq levee segment which lies be,tween 6th and 7th streets.
That le'ree also would need to be raised by about 1 foot in order
to have a full 3 feet of freeboard. The earthen mound between
the exil;ting USBR levees (from just past 7th street to just past
8th str.~et) would need to be rebuilt to a height of just under
4 feet. The existing USBR levee (upstream of 8th street to just
past 9th street) would require an additional 2.5 feet in height.
Upstream of the USBR levee, the existing mounds would need to be
rebuilt from 5 to 7.4 feet in height to the point just east of
the tO~l boundary (at cross section 22), where it would then tie
into hiqh ground on Highway 145. It is important to have any
future levee improvements tie in to hi.gh ground, at the
downstr,~am end, to prevent backwater flooding and at the upstream
end to prevent flanking.

Th,~ supplemental cross sections of the USBR levees which
were sUl:'Veyed for this study (and 1:hose done by the CWCB in 1985)
verify 1:hat the levees lack sufficient: height to meet minimum
FEMA requirements. These cross sect.ions along with a prOfile of
the cr01m elevations near the upstream end are compiled in
Appendi:c E. Further, previous studies make reference to the
earthen mounds being composed of unconsolidated-material and
could b,~ eroded by sustained high flows. ,The recent Corps Non-
Federal Levee Inspection Report (Appendix F) substantiates this.
The ear1:hen mounds appear to lack adequate density and cross-
section geometry. Waterside slope erclsion is evident in some
segment:; of the earthen mounds, highlighting the need for riprap
(or othBr form of erosion protecti<ln) in any future improvements.
Sloughing, voids, crown depressions, and animal burrows, as well
as dens,~ vegetation and brush, are evident in some port.ions of
the lev'~es and earthen mounds.

Given the above, it is believl~d not feasible to raise the
existinq earthen mounds (at least not 'without further, extensive

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