Advice on Storm-Related Flooding

By Denise DiFulco
Special to The Washington Post
Thursday, June 11, 2009

Never mind the heavy rainstorms of the past week: Hurricane season began June 1, and the National Oceanic and Atmospheric Administration is predicting a near-average year. That means a 70 percent chance of having nine to 14 named storms, four to seven of which could become hurricanes, including up to three rating a Category 3, 4 or 5, the most severe classification.

The Washington area is always a potential target for these tropical tempests, along with the flooding and power outages that result from high winds and heavy rain. Preparedness can go a long way toward keeping your home dry. Below are answers to frequently asked questions about flood risks, along with advice on what you can do to protect your home.

How do hurricanes cause floods in the home?

The ways in which water can enter your home during and after a hurricane are too numerous to list. If you live in a flood plain, chances are there's a body of water nearby that can overflow directly onto your property. There's only so much you can do in that situation.

Rain that falls heavily for a long period can force water into normally dry basements. That's because when the ground becomes saturated, hydrostatic pressure on foundation walls increases. "The water has to go somewhere," says Glen Izett, a manager for Phoenix Home Services in Burke. "It's going to take the path of least resistance." That path is frequently the joint between foundation walls and basement floors, Izett says. Any cracks in the foundation also can provide an entry point.

Can a sump pump prevent that from happening?

A sump pump is generally installed in the lowest part of a basement or crawl space in a pit dug into the ground. As water accumulates underground and hydrostatic pressure increases, water is forced into the pit. Once it reaches a certain level, the pump turns on and moves the water through a pipe away from the home. "Installed correctly, it relieves the pressure around the house," Izett says.

What about French drains? Do they provide more protection?

A French drain is a gravel-filled trench dug along the perimeter of a basement that redirects groundwater away from the home's foundation. Although a French drain can relieve hydrostatic pressure, installing one is an expensive and messy job that isn't right for all homeowners, Izett says. That's because the buildup of groundwater caused by rainfall isn't necessarily the only cause of the problem. Incorrect grading around a house, for instance, will cause water to accumulate and sit along foundation walls. There might also be cracks or other structural flaws in the foundation.

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