My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
FLOOD06287
CWCB
>
Floodplain Documents
>
Backfile
>
5001-6000
>
FLOOD06287
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
1/25/2010 7:08:31 PM
Creation date
10/5/2006 2:09:26 AM
Metadata
Fields
Template:
Floodplain Documents
Designation Number
488
County
Larimer
Community
Loveland
Basin
South Platte
Title
Flood Insurance Study - Loveland, Larimer County, Colorado
Date
3/23/1999
Designation Date
3/1/1999
Floodplain - Doc Type
Floodplain Report/Masterplan
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
23
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 />computer model (Reference 13). Flood profiles were drawn show- <br />ing computed water-surface elevations to an accuracy of 0.5 <br />foot for floods of the selected recurrence intervals. <br /> <br />Between approximately 850' downstream of Railroad Avenue and <br />West First Street, the la-year flood elevation is higher than <br />the 50- and lOa-year flood elevations, This is a result of <br />gravel mining in the area which has created levees that contain <br />the frequent flows and the effect of the narrow channel during <br />these frequent flows is a large backwater during the la-year <br />flood. During the 50-, 100-, and 500-year floods, flows overtop <br />the levees upstream of the area and flow into the flood overflow <br />channel, and the overbank flow is not restricted by the levees <br />creating less backwater effect from the channel. The la-year <br />flood profile is not shown in this area. For similar reasoning, <br />the 50-year flood elevation computed at cross-section H on the <br />Flood Profiles is slightly higher than the lOa-year flood <br />elevation. The 50-year flood profile is therefore drawn to <br />coincide with the lOO-year flood profile in this area. <br /> <br />Roughness coefficients(Manning's "n") were estimated by field <br />inspection. Roughness valves for the main channel of the Big <br />Thompson Ri ver ranged from 0.03 to 0,04; roughness va 1 ves for <br />the flood plain ranged from 0.04 to 0.08, <br /> <br />All elevations are referenced to the National Geodetic Vertical <br />Datum of 1929 (NGVD), formerly referred to as Sea level Datum <br />of 1929, locations of the elevation reference marks used in <br />this study are shown on the maps. <br /> <br />The hydraulic analyses for this study are based only on the <br />effects of unobstructed flow. Therefore, the flood elevations, <br />as shown on the profiles, are considered valid only if hydraulic <br />structures remain unobstructed. <br /> <br />4,0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />The National Flood Insurance Program encourages state and local <br />governments to adopt sound flood plain management programs. There- <br />fore, each Flood Insurance Study includes a flood boundary map <br />designed to assist communities in developing sound flood pl~in <br />management measures. <br /> <br />4.1 Flood Boundaries <br /> <br />In order to provide a national standard without regional dis- <br />crimination, the lOa-year flood has been adopted by FEMA as the <br />base flood for purposes of flood plain management measures. <br />The 500-year flood is employed to indicate additional areas of <br />flood risk in the community. For each stream studied in detail <br />the boundaries of the 100-year and 50D-year floods have been ' <br />delineated USing the flood elevations determined at each cros<; <br /> <br />7 <br />
The URL can be used to link to this page
Your browser does not support the video tag.