You are not on the FEMA website.  TOUCH FEMA home to go to the FEMA official website.

[CONSERVATIONTECH.COM-Home]     [ FEMA home (www.FEMA.gov) | FEMA Library (www.fema.gov/library/index.jsp)]


WEB-BASED HANDBOOK (Legacy Edition). CLICK HERE to submit comments.
Because of staff changes and Randolph Langenbach's retirement from FEMA, these handbooks were never published on the FEMA website.  These are the only copies available.


 

Chapter 4: BUILDINGS

B. High Velocity Flows

 

Introduction

Problem:

High velocity flows can scour the soil from under and around footings, threaten the building's structural integrity, and even knock buildings off of their foundations.

Mitigation Objective:

Protect building facilities from damage due to erosion caused by high velocity flood flows.

B.1 Construct Piling or New Spread Footing

Building foundations can be undermined due to high velocity flows that scour away the soils supporting the foundation. By constructing a piling or new spread footing, the foundation is supported, thereby preventing failure in subsequent flooding.

image096.png (39520 bytes)

Effectiveness:

  • Very effective

Limitations:

  • Spread footings should not be used in a coastal environment.
  • Area may be inaccessible to pile driving equipment.
  • Pile driving may cause damage to adjacent facilities.

Considerations:

B.2 Replace Footing Materials

To better secure footings and the surrounding material, replace lost footing material of soil or gravel with concrete or grouted granular fill. Soil consolidation and settling caused by inundation, or erosion of the soil due to flow past the footing, can often undermine the soil beneath the footing, which creates a space between the bottom of the footing and the top of the soil beneath the footing.

image099.png (36986 bytes)

Effectiveness:

  • Very effective

Limitations:

  • May not be effective if future erosion cannot be controlled, or, if in the case of inundation, soil consolidation is not complete.

 

 

NOTE:  None of the mitigation measures in these Handbooks should be considered ‘pre-approved’ or otherwise automatically eligible for FEMA funding. Only FEMA staff can determine eligibility, once they have determined that an applicant is eligible and they have reviewed a project proposal.

FEMA HAZARD MITIGATION HANDBOOKS                                                                        Updated: June 13, 2002