Rain Gardens
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A rain garden acts like a native forest by collecting, absorbing, and filtering stormwater runoff from roof tops, driveways, patios, and other areas that don’t allow water to soak in. Rain gardens can help clean up the Sound and protect aquatic life. When it rains or snows, more water flows from developed areas than undisturbed areas, carrying oil, fertilizers, pesticides, sediment and other pollutants downstream.
Rain Garden BasicsWhat is a rain garden?A rain garden is a beautiful and effective way to clean polluted stormwater runoff. A rain garden acts like a miniature native forest by collecting, absorbing, and filtering stormwater runoff from roof tops, driveways, patios, and other areas that don’t allow water to soak in. They can be built at several scales and one may be just right for your home or neighborhood.
Rain Gardens are simply shallow depressions that:
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Why are Rain Gardens Needed?
Stormwater is nothing but rainfall after it falls on the earth’s surface and travels across the landscape to a nearby stream or other water body. In landscapes that have been altered by humans, this stormwater picks up everything we humans leave behind – things like oil and gas, heavy metals, fertilizers, and animal waste.
Scientists have confirmed that stormwater is harmful to humans, animals, and fish that come in contact with it. Eventually stormwater makes its way to estuaries and oceans, impairing water quality, impacting our shellfish and fisheries industry, and limiting recreational opportunities.
Research and experiments have shown that stormwater collected from highways is lethal to fish. However, when that same stormwater was filtered through a special rain garden soil mix – the fish lived. Rain gardens can be a important tool in limiting the amount of contaminated water reaching our streams,rivers and oceans.
Scientists have confirmed that stormwater is harmful to humans, animals, and fish that come in contact with it. Eventually stormwater makes its way to estuaries and oceans, impairing water quality, impacting our shellfish and fisheries industry, and limiting recreational opportunities.
Research and experiments have shown that stormwater collected from highways is lethal to fish. However, when that same stormwater was filtered through a special rain garden soil mix – the fish lived. Rain gardens can be a important tool in limiting the amount of contaminated water reaching our streams,rivers and oceans.
Getting Started
To help contribute to water and soil conservation, you can implement these easy measures:
1. Create bermed areas on your property that will help slow rainwater run off. This can be as simple as using some dirt to make a berm and reinforce it with dead twigs and/or branches as the beavers would have done. Piling rocks on each side will help reinforce the berm until grasses and other plants have a chance to establish a foot hold and help stabilize the berm and prevent erosion with their root structures.
2. Consider creating a pond. It could be either a small yard pond, a simple open barrel that collects rainwater if you live where you where you only have access to a balcony or patio, or create a holding tank or large pond if you have acreage.
3. By allowing sediment to collect in your pond, it will decompose and become soil. After a period of time you will occasionally want to dredge your water collection area and can use this very rich and organically created soil as an amendment to your garden soils.
1. Create bermed areas on your property that will help slow rainwater run off. This can be as simple as using some dirt to make a berm and reinforce it with dead twigs and/or branches as the beavers would have done. Piling rocks on each side will help reinforce the berm until grasses and other plants have a chance to establish a foot hold and help stabilize the berm and prevent erosion with their root structures.
2. Consider creating a pond. It could be either a small yard pond, a simple open barrel that collects rainwater if you live where you where you only have access to a balcony or patio, or create a holding tank or large pond if you have acreage.
3. By allowing sediment to collect in your pond, it will decompose and become soil. After a period of time you will occasionally want to dredge your water collection area and can use this very rich and organically created soil as an amendment to your garden soils.
4 Stages to building and sustaining a rain garden
I. Plan
- Check with your local municipality to confirm requirements for your project.
- Confirm the location of existing utilities and avoid conflicts.
- Determine how much contributing area will drain to your rain garden.
- Observe how drainage flows from the contributing area and pick a location to capture the runoff.
- Test the soil drainage rate in that location to be sure rain will soak into the ground.
- Identify a safe place to direct overflow.
- Determine the size and shape of your rain garden.
- Confirm that the selected location will accommodate the rain garden.
- Lay out your rain garden using stakes, rope, ground paint, and/or other tools.
- Excavate the soil.
- Create an entry for water (extended rain gutter downspout, pipe, swale, rain chain, or landscaped area) into your rain garden.
- Level the excavated bottom of your rain garden (but do not compact the soil).
- Provide a rock-lined overflow.
- Obtain an approved rain garden soil mix or mix compost into your existing soil. Make sure any compost used that contained manure is very mature.
- Place the soil mix and leave space below the overflow for ponding.
- Level the surface of the rain garden soil mix, and be sure not to over compact the soil.
- Use a variety of small trees, shrubs, groundcovers, and grasses. The denser the mature coverage, the less you will have to deal with weeds.
- Select plants suitable for the three planting zones within your rain garden and around the perimeter.
- Cover exposed soil with mulch to minimize erosion and weeds.
- If needed, provide water to establish plants.
IV. Maintain
Maintaining Mulch
A newly planted rain garden should have mulch between the plants. The mulch may be coarse wood chips or coarse compost, or a combination of mulches for different parts of the garden. Mulch helps prevent weeds, prevent erosion, and reduce watering needs.
The parts of the rain garden where water goes in or out should have cobbles or drain rock or some other material–referred to as “armoring”–to prevent erosion from the water flow. In some, there might be raised overflows covered with a grate.
- Keep inlet and overflow clear of debris and well protected with rock.
- Pull weeds early and often to keep them from spreading.
- Maintain sharp edging to prevent grass from infiltrating your rain garden
- Do not use fertilizers, pesticides, or herbicides.
- Provide water as needed.
- Provide additional mulch as needed.
Maintaining Mulch
A newly planted rain garden should have mulch between the plants. The mulch may be coarse wood chips or coarse compost, or a combination of mulches for different parts of the garden. Mulch helps prevent weeds, prevent erosion, and reduce watering needs.
- Check the mulch and replenish it when needed.
- Spread by hand to avoid damaging plants.
- The mulch should be 2 to 3 inchesthick between plants,with no bare soils howing.
- The mulch should be lightly applied right around the base of plants,and not touching woody stems.
- Less mulch will be needed over time as the rain garden fills in and there are smaller spaces between plants.
The parts of the rain garden where water goes in or out should have cobbles or drain rock or some other material–referred to as “armoring”–to prevent erosion from the water flow. In some, there might be raised overflows covered with a grate.
- Sometimes the armoring gets moved after heavy storms. Check to be sure it is still thickly applied—you should see no bare soil below.
- The armoring should be clean. If you see silt or mud on top of the armoring, this will have to be removed, and it may be a sign that sediments are flowing into the garden. Find the sediment source and prevent it from entering the garden in away that won’t impact the flowof stormwater into the garden.
- Always check any inflow pipes to be sure nothing is blocking the free flow of water into the garden.
- Clean fallen leaves off of overflow grates and keep plantstrimmed back to prevent blocking.
- Towork properly,the rain garden should have dense plant coverage (80-100%)in the bottom.
- If plants die,they will need to be replaced with othersthat will be more successful.
- Note plant health and vigor at each visit; address any concerns before
A rain chain directs rain from a roof into a small holding pond. The pond then gently overflows into a swale
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The swale then overflows into a gentle slope where thirsty plant roots help slow and capture the runoff. Vegetables and herbs are planted at the bottom of the slope.
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The rain chain becomes an item of interest in the winter
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