Designing Buildings to be Flood Resistant

Flood Resistant Design

by Kim Coates

The Mississippi River (the second longest in the U.S) flooding recorded in 1993 is consider to be the most devastating in recorded U.S. history.  Damage estimates creep towards $20 billion and over 50 people lost their lives. Continued flooding in flood hazard areas brought the need for flood resistant buildings and structures sharply into focus.

Since 2000, the IRC and IBC (International Residential Code and International Building Code) have included provisions to address buildings and structures located in flood hazard areas, including those prone to high-velocity wave action, such as the Gulf and Atlantic coasts where hurricanes occur. In the most recent version, 2015, the IRC and IBC require that buildings and structures proposed to be constructed in flood hazard areas must be designed in accordance with ASCE 24, Flood Resistant Design and Construction.  Also, the provisions include any building or structure already built, but requiring “… substantial improvement and restoration of substantial damage of buildings and structures in flood hazard areas shall be designed and constructed in accordance with the provisions …” (2015 International Residential Code, Section R322.1, and similar found in 2015 International Building Code Section 1612.1).

ASCE 24 doesn’t just cover items such as load and force (ASCE 24 references ASCE 7 Minimum Design Loads for Buildings and other Structures for calculations for Hydrodynamic Loads, Wave Loads, etc. ), but building performance, flood-damage resistant materials, protection of utilities and water supply and construction site considerations. The following are just a few of the requirements and considerations ASCE 24 helps you with:

• Amount of freeboard needed
• How to consider soil characteristics such as consolidation, expansion, erosion, liquefaction, etc. when designing for foundation performance
• Flood opening requirements
• Where to place mechanical systems such as heating, ventilation and air conditioning
• Types of materials allowed in areas exposed to salt water
• Fuel supply line safety requirements
• Siting considerations
• Pool regulations

ASCE 24 is a complement to, rather than a repeat of, the NFIP (National Flood Insurance Program) regulations. It adds some additional requirements, as well as providing clarity to some portions and also some limitations. These additional requirements and clarity help make buildings designed according to ASCE 24 better able to withstand flood loads and damage, which can help reduce the financial cost of flooding, as well as the devastating cost in loss of life.

NTA has engineers who are experts in flood resistant design. Contact us today for more information.