Why does my yard flood after it rains, and how do you fix it?

First: your yard, or the whole street?

In a big storm a whole neighborhood can sit under water because the system itself is full. In August 2024, with streets flooded, the Town of Mount Pleasant said most problems weren't clogged drains: the drainage systems were full, and the ponds and wetlands around them were at capacity. Nothing done in one backyard changes that.

What can be fixed is water that sits in your yard after an ordinary rain, or water that heads for your house.

Why water sits where it does

• It stands in a low spot. The ground slopes so the water collects instead of leaving.
• One spot never dries out. Often a pocket fed by a downspout or a neighbor's slope. Sometimes it's the water table close to the surface, which is a different problem.
• It runs toward the house. Common in older yards where beds have been topped up with soil and mulch for years, until the ground by the wall sits higher than it should.

How much should the yard slope away from the house?

The residential building code's minimum is 6 inches of fall within the first 10 feet out from the foundation (IRC R401.3). Where the lot is too tight or too flat to get that, a swale or a drain has to carry the water away instead.

Regrade it, or drain it

Why do French drains fail here?

Usually because the water had nowhere to go. A drain needs an outlet lower than the problem, and with a high water table a trench dug too deep simply fills from below. Filter fabric matters too: without it, sandy soil washes into the stone and clogs it over time.

Can I drain my yard onto the neighbor's?

Not as concentrated runoff. Mount Pleasant's single-family stormwater guidance says runoff cannot be concentrated onto lower neighboring property, and downspouts cannot discharge within 10 feet of a shared property line. Drainage has to end somewhere it is allowed to: a ditch, a storm drain, or ground that can take it.

Permits

Regrading on a single-family lot in Mount Pleasant needs the Town's stormwater management and tree preservation permit before the work starts, and it gets checked before anything is scheduled.

What Josiah looks at on a visit

Where the water actually collects, where it could go instead, and how much fall there is between those two points.