My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
FLOOD10728
CWCB
>
Floodplain Documents
>
Backfile
>
11001-12000
>
FLOOD10728
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
11/23/2009 2:18:36 PM
Creation date
6/12/2007 3:30:25 PM
Metadata
Fields
Template:
Floodplain Documents
County
San Juan
Community
San Juan County and Unincorporated Areas
Title
FIS - San Juan County and Unincorporated Areas
Date
3/1/1978
Prepared For
San Juan County
Prepared By
FEMA
Floodplain - Doc Type
Current FEMA Regulatory Floodplain Information
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
36
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
<br />Roughness coefficients (Manning's "nil) were estimated by field <br />inspection at each cross section and checked for reasonableness <br />against a recognized standard text (Reference 11). Roughness values <br />for the main channel ranged from 0.035 to 0.05; roughness values for <br />the flood plain ranged from 0.035 to 0.06. <br /> <br />Water-surface profiles of the selected recurrence intervals were <br />developed using the u.s. Army Corps of Engineers HEC-2 step-backwater <br />computer model (Reference 12). <br /> <br />Flood profiles were drawn showing computed water-surface elevations <br />to an accuracy of 0.5 foot for floods of the selected recurrence <br />intervals (Exhibit 1). Starting elevations were based on slope-area <br />method. <br /> <br />The flood profiles shown in this report are based on the effects of <br />flow through unobstructed hydraulic structures and are, thus, <br />considered valid only if these structures remain unobstructed and do <br />not fail. <br /> <br />Along Cement Creek, the adjacent properties are approximately at the <br />same elevation as the streambanks. Once the floodwater overflows <br />the banks, it will spread over a wide area with very shallow depth <br />(less than 1 foot). According to the computational results, the <br />creek can pass the 10-year flood without overflowing. For 50- year <br />and lOO-year floods, the floodwater overflows just upstream of the <br />14th Street bridge (Bridge No.5) (between cross sections 305 and <br />306) and spreads over the adjacent ground. For SaG-year f~ood, the <br />floodwater starts overflowing at the State Highway 110 bridge (Bridge <br />No.6). Flood profiles for Cement Creek were determined with flows <br />staying in the creek only. For the downstream portion from 14th <br />Street bridge, the profiles for 50-, 100-, and 50G-year floods <br />approximately coincide because of limited channel capacity, and only <br />the 50-year flood profile is shown. <br /> <br />On Mineral Creek, the SOD-year flood overflows u.S. Highway 550 <br />(between cross sections 207 and 208) and spreads over the area from <br />sewage lagoons to the Denver and Rio Grande Western Railroad with an <br />average depth of 0.5 foot. The SOO-year flood profile downstream <br />from cross section 207 was computed using only the flow remaining in <br />the creek. <br /> <br />At the Denver and Rio Grande Western Railroad where Mineral Creek <br />joins the Animas River, part of both the 100- and SOD-year flood- <br />flows in Mineral Creek would enter the Animas River, while part <br />would remain west of the railroad tracks. The flooding west of the <br />railroad tracks was determined to be shallow, with depths estimated <br />at 1.5 feet. <br /> <br />10 <br />
The URL can be used to link to this page
Your browser does not support the video tag.