Rainwater Dispersion

Rainwater is a resource to be preserved and protected, not a nuisance to be eliminated. 

In all but the driest areas, rainfall provides much of the moisture in the soil and helps keep underground aquifers full. Helping rainwater disperse more effectively into the soil is better for everyone.

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NOTE:

All development within the special flood hazard areas (SFHA) must incorporate low impact development techniques where feasible to minimize or avoid stormwater effects. With various elements of low impact development (LID), most projects on parcels ½ acre in size or larger in rural areas can often meet these requirements by using dispersion as follows:

LID  Dispersion worksheet

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Depending on the soil type that you have, your water movement will be affected in certain ways. If your soil is predominantly sand, you are not likely to have flood issues, but may struggle to retain water, because sand’s large particles let water through easily. If you have predominantly clay soil, your soil’s tiny particles hold water very easily, become waterlogged quickly, and then tend to let water run off the surface thereafter.

Learn how to determine Soil Type

 

The Goal

Slow water flow

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Let the landscape to work for you.

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Parking lot raingarden. 

Reduce the pressure

Fast-moving water

is a powerful thing. Unchecked in nature, it takes water from where it is needed, such as aquafers, and flows where it can cause damage to landscapes and cause soil erosion, which decreases soil fertility 

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Surface water flows downhill from the highest part of your land (the watershed) to the lowest parts in all directions, and follows the path of least resistance as decided by gravity.

One way to slow the water flow is to use mounds and valleys to intercept it. When the water flow slows, it has more time to be absorbed into the soil.

Filter

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When water slows, it percolates into the ground and recharges our aquifers, it keeps nutrients in place, and feeds our plants. These conditions can cause plants to grow stronger root systems. It also means the plants will need less supplemental water because the soil is staying moist.

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Curb-cut raingarden

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Urban raingarden

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Urban raingarden

Help your landscape to work for you.

  • Retain trees and other vegetation which intercept precipitation with the tree canopy, leaves, and roots. 

  • Grade only as much of the land as needed so soil, terrain, and plants can slow runoff and hold water until it is absorbed into the soil. 

  • Direct water runoff from roofs, pavements, and similar impervious surfaces to rain catchments or planted areas that can benefit from the water. 

  • Create beautiful and useful outdoor spaces that limit lawn and other compacted areas while maintaining soil that can absorb water. 

  • Place driveways and parking areas thoughtfully to limit compacted soil and direct runoff to planted areas.

  • Use natural mulch to improve soil's ability to absorb and filter water.

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As a final word on soils and their water-harvesting potential, what is on top of the surface of the soil matters as much as the type of soil.

Mulched soils not only slow the speed of water flow, but they also lose much less water to evaporation, so mulching as a technique is highly recommended for water-wise gardens