Time to rethink floodproofing

The need for quick-deployment solutions
Recognizing the weaknesses in existing flood mitigation technology, new dry floodproofing methods have emerged in the form of flexible barriers offering versatility and resiliency. Using soft goods, as opposed to hard metals, allows for a flood mitigation system providing full flood protection, employing equipment that could be stored in place and deployed rapidly by building maintenance or security staff.

System design objectives for these new technologies were established after a careful analysis of available systems and field assessments following Superstorm Sandy. They include:

  • point-of-use storage (allowing the facility to stay open until the last possible moment, and reopen faster for higher business continuity);
  • quick-deployment architecture to ensure minimal setup and quick retraction;
  • low operational impact (i.e. simple to install, requiring only one or two people to deploy);
  • low stowed volume to fit in tight spaces located at the point of use;
  • low maintenance based on minimal mechanical complexity;
  • high reliability via simple designs and robust construction;
  • lightweight materials to facilitate both safe and rapid manual operation;
  • conformal materials adaptable to any opening; and
  • scalability (i.e. able to be easily sized and configured to structural profile and expected loading, capable of protecting more than 4.3 m [14 ft] of flood height).

Flood mitigation products have various application points, including the following:

  • building entrances;
  • stairwells (see “Customizing a Stairwell Solution”);
  • doors;
  • windows and curtain walls;
  • storefronts;
  • below-grade window wells;
  • ventilation shafts;
  • intake/exhaust openings;
  • parking garage and loading dock portals;
  • vehicular entrances;
  • emergency exits; and
  • rail and vehicular tunnel portals.

The new solutions to address these points include flexible walls, gates, covers, and plugs—together, these represent an advanced structural technology that can meet resiliency needs.

For commercial and government buildings, the most commonly used new technology are flexible wall barrier systems. These employ flexible Kevlar composite or polyester webbing woven into an extremely tough mesh fabric with a PVC-coated polyester to serve as the water barrier retention layer. The resulting soft goods combination can hold up to micrometeorite impact testing. (For more on this, visit www.nasa.gov/centers/wstf/laboratories/hypervelocity/mmod.html and en.wikipedia.org/wiki/Thermal_Micrometeoroid_Garment.)

The flexible wall barrier is supported by rugged structural members (steel or aluminum, depending on the application needs), but with its soft goods base, the system can be deployed easily by one or two persons, often in minutes. Even a full-perimeter, 2.4-m (8-ft) flexible wall barrier can be erected around a typical commercial building in a matter of a few hours, because all materials are stored at the point of use, and only have to be extended and locked in place.

Once conditions are safe, the flexible wall systems can be stowed as efficiently as they are deployed. After a flood, normal business operation can resume in hours or a couple of days depending on cleanup requirements— rather than the weeks required to clean, dismantle, and cart the components of traditional stop-log or aluminum-plate systems to storage facilities. If no flooding occurs, the flexible wall stows quickly; normal operations can usually be resumed in about the same time required to deploy.

The barrier system is typically installed in a horizontal trench just below grade, or in a vertical container installed at the side of a doorway or portal opening. As the wall material is flexible, it can be packed into a small container. For instance, the flexible barrier portion of a 2.4-m vertical wall can fit in a space of 200 x 200 mm (8 x 8 in.). Total trench cross-section can then be the 200 x 200-mm space for the wall, plus enough additional space for the support posts, lying flat. With such small size, the flexible wall barrier system requires minimal infrastructure modification for installation. The wall can also be scaled in height and length to fit any application and is self-contained; therefore, no special tools 
or training is required for operation.

A variation of this design is also available in a rolled-up version, which makes it ideal for certain historical applications where modifications to the building are limited due to preservation requirements. This is also suitable for existing buildings seeking to minimize modifications.

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