My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
FLOOD05464
CWCB
>
Floodplain Documents
>
Backfile
>
5001-6000
>
FLOOD05464
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
1/25/2010 6:49:19 PM
Creation date
10/5/2006 1:33:41 AM
Metadata
Fields
Template:
Floodplain Documents
County
Statewide
Basin
Statewide
Title
Reducing Losses In High Risk Flood Hazard Areas: A Guidebook For Local Officials
Date
1/1/1985
Prepared For
FEMA
Prepared By
Association of State Floodplain Managers
Floodplain - Doc Type
Educational/Technical/Reference Information
Jump to thumbnail
< previous set
next set >
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
229
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 /> <br />FLOODING DUE TO GROUND FAILURE: SUBSIDENCE AND LIQUEFACTION <br /> <br />Subsidence occurs in parts of all fifty states. The problem is particularly serious in <br /> <br />southern California, the Houston-Galveston area and southern Louisiana. Lowering of the <br /> <br /> <br />land surface - caused by extraction of subsurface fluids and other materials, soil com- <br /> <br /> <br />paction or other processes - can increase flood depths and duration. <br /> <br /> <br />Liquefaction occurs when unconsolidated sands and silts temporarily flow like <br /> <br />thick fluids, usually triggered by earthquakes. Liquefaction can be a major cause of <br /> <br /> <br />flooding if dams or levees are damaged or if structures on filled wetlands sink below <br /> <br /> <br />water level. <br /> <br />FLUCTUATING LAKE LEVELS <br /> <br />Thousands of inland lakes, inCluding the Great Lakes and the Great Salt Lake, are <br /> <br /> <br />subject to long-term fluctuations in water levels. Recent fluctuations of the Great Salt <br /> <br /> <br />Lake have caused over one hundred million dollars in losses in a single year. Lake levels <br /> <br /> <br />can rise and remain high for years, with damage compounded by ice and shore erosion <br /> <br />and detrimental impacts on water quality. <br /> <br />ICE JAMS <br /> <br />Thirty-five northern and midwestern states suffer high risk flooding due to ice <br /> <br /> <br />jams. Dams of ice increase flood levels upstream, then unleash ice floes and deep, high <br /> <br /> <br />velocity floodwaters downstream. The combination of ice, debris and water can cause <br /> <br /> <br />tremendous physical damage to structures. <br /> <br />MUDSLIDES <br /> <br />Heavy rains can trigger mud floods or mudflows in areas of steep slope, limited <br /> <br /> <br />vegetation and unconsolidated soils. Flows can be sudden and deep, but the greatest dam- <br /> <br /> <br />age is often done by the debris. Mudflows and mudfloods are a particular problem in <br /> <br /> <br />Southern California, the San Francisco Bay area and the communities surrounding the <br /> <br /> <br />Great Salt Lake. <br /> <br />A-3 <br />
The URL can be used to link to this page
Your browser does not support the video tag.