Tips for managing rainwater in your landscape

Story and Photos by Susan Jasan

It seems lately that spring brings torrential storms to many regions of the country. Often owners are faced with raging waters where previously there had been none, or even worse, moisture in their homes where previously all was well.

It’s great when we have water where we want it; however managing the flow of storm water is imperative to protecting one’s home and property. 

Water management is a science. Civil engineers as well as landscape architects are trained to understand storm water management, drainage, and how to address and hopefully prevent “water problems.” There are some general guidelines to keep in mind as you review options for managing rainwater. Whenever in question, call the pros!

Water runs downhill. It’s simple. It’s obvious. But sometimes, actually often, the obvious is not readily apparent. When determining where you want to direct your water you need to know where it is coming from and how much water you will need to manage. The typical homeowner usually considers the water from their roof and water flowing down from an uphill neighbor. How far does that water travel? Is the water coming from a 1-acre lot or a 10-acre lot?

Diverting downspouts through underground piping is often a viable option. Just be sure that the water can discharge easily from an open pipe down a slope and away from the potential to cause any harm.

Know if you have a drainage easement on your property, and if so, keep it open so it can function as it was designed to protect your property and others. 

Maybe there’s a tiny creek that meanders through the neighborhood. Take a good look at that creek: Are the sides of the creek wide and quite possibly eroded? If so, beware! That little creek may become a roaring river during a torrential storm, potentially spilling over its banks. Check with local authorities to see if that little creek might likely be a floodway or a flood plain and plan accordingly.

Depending on the volume of water, large drainage grates are sometimes necessary to divert water and protect property.

If nearby surfaces are impermeable (sidewalks, patios, roofs, etc.), in other words the surfaces are hard and the water cannot soak through to the subsoil, then the amount of water and the speed of the water flow will be much greater than if that same area has vegetative cover. 

It’s actually been documented that an area of woodland with tree cover will slow the rate of the rainfall as it hits the woodland floor. As much as 40 percent of the rainfall is captured in the canopy of the trees and never reaches the ground. Surely you’ve ducked under a large tree during a light rainfall to stay dry – while the paved surfaces around you were wet! Another example of Mother Nature’s brilliance is how the leaf litter on a woodland floor prevents erosion.

The location of this downspout at the base of a retaining wall and on top of the home foundation isn’t ideal. A simple extension would help protect both structures and divert the water away from the house foundation downslope.

To slow the water, you want to widen the area over which it flows. When you channel water into a narrow space it both concentrates the flow and increases erosion potential.

If you move water from your downspouts into pipes that run underground and away from structures, be sure the pipes are large enough and always kept open and free of debris. Clogged piping is often the culprit for many problems created by water. All too often the discharge end of a pipe becomes buried by topsoil, mulch, silt, and debris. Be sure to keep the ends of pipes clean and open to allow free-flowing drainage.

These pipes daylight into a rock detention basin to slow storm water from above before the water continues downslope, and in this case, into a lake.

If you are routing several downspouts together into one pipe, you should significantly increase the pipe size at the junction with a larger pipe in order to accommodate the larger volume of water. If long lengths of pipes run underground for a significant distance, be sure to include a clean-out connection. It’ll prevent lots of headaches later.

Our plants thirst for water, but just the right amount. Rainwater from a rain barrel is used here to help water this Schefflera, which is located on a deck away from convenient spigots.

Consult a civil engineer or landscape architect if you’re unsure about appropriate pipe sizes for the amount of water on your property. There are many factors that determine appropriate pipe size. 

If you’re unsure about drainage around your home, it is always a good idea (and investment) to consult a professional. All too often, a small drainage problem can become a large problem when storm water begins to flow.

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