FLOOD09322

• County: Rio Blanco
• Community: Rangely
• Stream Name: White River
• Basin: Yampa/White
• Title: White River at Rangely
• Date: 10/1/1993
• Prepared For: Rangely
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Floodplain Report/Masterplan

Table 3
100-Year Flood Water Surface Elevations
with EXisting Levee
(No Levee Condition is Restored FIS File)

Cross ~:ection

Computed 100-Year Water Surface
Elevations {in feet m.s.l.l
With Levee No Levee

33.2
36.0
37.0
38.0
39.0
40.0
41. 0
42.0
43.0
44.0
45.0
46.0
47.0

5204.59
520!;.57
5205.75
5206.06
5207.63
5209.08
5210.32
5211. 82
5213.48
5214.57
5215.63
5218.37
5219.35

5204.59
5205.57
5205.75
5206.06
5207.63
5209.08
5210.32
5211. 73
5212.97
5214.13
5215.70
5218.34
5219.34

on the levee lacked the necessary amount of freeboard. During the
100-year flood event, several locations along the levee lacked the
necessary freeboard. For the 100'-y,~ar event, the most. upstream
point 1dthout adequate freeboard was located near the ju.nction of
the or:lginal filtration plant levee with the 1986 extension. This
result:; in the levee being considE~red failed at that loca.tion and
the en1:ire extension being considered ineffective for the lOO-year
flood event. At the 500-year flood event, the levee was almost
overtopped in several places.

D,)wnstream from the end of the existing levee, flood\~aters are
free to spread south from the Whi.te River toward Rangely. Comparing
.the topographic mapping of the area with t:he computed water surface
elevations for the 10-, 50-, 100--, and 500-year flood events shows
that at about the 50-year flood e,vent, floodwaters will begin to
enter ":he developed area of Rangely. Because of the conf iguration
of the existing levee, floodwaters (~an back up on the landwa.rd side
of the levee at the water surface elevation found at the downstream
end of the levee, as no tie-off exi:sts there. For t:he 100-year
flood ,~vent, the water surface elevation computed at cross section
42 nea:r the north end of the levee 1IIaS 5211.8 feet m.s.l. The 100-
year flood water surface elevation computed at seGt:ion 41 was

8