Flood and Wind Resilient Construction

You can try the sand bag shelters.

The first issue is not the build in a flood prone area! This may sound obvious but people may have no choice due to poor transport to work or bad planning. Look at these non-technical factors and see if you can find why people are settling in inappropriate places.

For flooding, it depends on the speed and level of inundation. Is it long term slow inundation in the rainy season or danger of rapid overland flow in storms? Raising the ground level for the building may be enough to avoid shallow flooding. If the building is going to repeatedly flooded, a good foundation and lower wall is a good start, even if the rest of the structure is not so robust. This can prevent damage for minor flooding and can help the home be restored quickly after a larger event. If there is flash flooding, bunds (shallow banks) can divert surface flows away from the most vulnerable areas.

But do see if people can be relocated!

The first issue is not the build in a flood prone area! This may sound obvious but people may have no choice due to poor transport to work or bad planning. Look at these non-technical factors and see if you can find why people are settling in inappropriate places.

For flooding, it depends on the speed and level of inundation. Is it long term slow inundation in the rainy season or danger of rapid overland flow in storms? Raising the ground level for the building may be enough to avoid shallow flooding. If the building is going to repeatedly flooded, a good foundation and lower wall is a good start, even if the rest of the structure is not so robust. This can prevent damage for minor flooding and can help the home be restored quickly after a larger event. If there is flash flooding, bunds (shallow banks) can divert surface flows away from the most vulnerable areas.

But do see if people can be relocated!

The first issue is not the build in a flood prone area! This may sound obvious but people may have no choice due to poor transport to work or bad planning. Look at these non-technical factors and see if you can find why people are settling in inappropriate places.

For flooding, it depends on the speed and level of inundation. Is it long term slow inundation in the rainy season or danger of rapid overland flow in storms? Raising the ground level for the building may be enough to avoid shallow flooding. If the building is going to repeatedly flooded, a good foundation and lower wall is a good start, even if the rest of the structure is not so robust. This can prevent damage for minor flooding and can help the home be restored quickly after a larger event. If there is flash flooding, bunds (shallow banks) can divert surface flows away from the most vulnerable areas.

But do see if people can be relocated!

FEMA (Federal Emergency Management Agency) deals with flooding issues in the U.S. They have some online documentations that can be helpful. Usually, for a residential structure, they mandate the lowest floor of the structure to be built above the base food elevation (BFE), which is the rise of floodwaters during a 100-year storm event, a rainfall that has a 1% chance of occurring per year. This can be the 1% rain event during a six-hour storm, e.g. 4.5 inches, etc., that will go into estimating/calculating the amount of flow at a specific discharge point in the watershed. Thereupon, they use the flow value in hydraulic calculation to estimate the rise of floodwaters under such severe (1%) circumstances. There are two (2) freewares that can help you with ths: HEC-HMS for flow computation and HEC-RAS for the floodplain/hydraulics; both are reliable softwares overseen but the U.S. Corps of Engineers (USACE). You will need some topographical maps of the location. If no such information available, you can guestimate the height of floodwaters by observing previous flooding events. Regardless, build above the BFE, then the foundations must withstand the flow that goes at it; the practice that FEMA had was one square-inch opening per square-foot of floor area. Thus, no hydrostatic pressure will be built against the foundation. The FEMA guidelines are written for the homeowners and explains it to anyone from any educational background.