How I Prepare for and Prevent Garden Flooding

As a permaculture designer, managing water is a key challenge for me to solve.

heavy rain in the backyard

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Surface flooding can be a major issue in gardens. As a permaculture designer, managing water is a key challenge for me to solve. One of my jobs is to look at the landscape, terrain, and surroundings to develop strategies to deal with a deluge. So today I thought I would share some basic tips to help you prepare for and prevent flooding in your garden.

1. Deal With Water From Roofs on Your Property

One thing that is crucial in managing water on your property is collecting the water that falls onto the roof of your home and other structures. Make sure that gutters are clear and drains are following as they should. Remember, it is always best to catch and store rainwater, keeping whatever you can store safely on your property—perhaps in containers or tanks, but also in the soil and plants. Be sure to direct and make use of rainwater, rather than allowing it to pool as it will during heavy rain.

rain gauge

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2. Look at Areas of Hard Paving (and Consider Reducing Them)

Another basic necessity in flood-prone areas is thinking about areas of hard paving. Paved areas that cannot drain freely cause surface runoff. They have the potential to focus floodwaters and make flooding issues more pronounced. Roads, parking areas, and driveways that cannot absorb water worsen issues, so wherever possible use permeable paving or, better yet, remove unnecessary surfaces and replace with plants.

3. Add Drainage and Direct Water Wisely

Some areas can flood even without issues of water from roofs and paved areas. In all design work, looking at water and how it moves through and across a landscape is hugely important. In order to garden effectively in flood plains or waterlogged, boggy areas, earthworks are often required to shape the landscape and manage water flow. 

French drains (or drainage ditches) are commonly used to keep waterlogging and flooding to a minimum. It is very important to think about how and where exactly water is directed. 

The best design options work with the terrain, and often it is best to keep water on-site, where it can be utilized later. It might be directed to tanks or cisterns, to reservoirs on larger properties, or to garden ponds. It could also be directed to rain gardens or dedicated wetland areas to catch and conserve more water in plants and soil. A flood management plan often involves creating wetter zones in the garden, and directing water to these areas to keep other areas less sodden.

paved outdoor area

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4. Consider Contouring Land to Manage Water

In addition to drainage ditches, there are other earthworks to consider. To garden successfully in flood-prone areas, it is important to look at existing water patterns before designing a scheme to prevent runoff and erosion and to manage water more effectively on a property. 

On sloping sites, slowing water flow can be just as important as removing excess water to a more suitable location. Terracing and on-contour swales (low places) must be carefully designed in high water areas. But implementing them correctly—with spillover to a pond, perhaps, during flooding events—can provide solutions to improve a garden.

Digging basins with surrounding berms, to create wetlands or rain gardens, can also be an initial stage in creating a garden that is productive and beautiful even during flooding events.

5. Choose Planting Schemes That Absorb More Water Than Lawns

Rain gardens and other diverse planting schemes can absorb 30% more water than boring monocrop lawns. Neat grass lawns are not only harmful and fragile systems, but they reduce the land's capacity to catch and filter rainfall. So if you want to create a flood-resilient garden, ditching the lawn may be a good way to go.

If you live along a stream, river, or other waterway that could flood, riparian planting (aka planting along the edge of a river) is hugely important. Trees and shrubs and other vegetation along its banks will serve as a buffer between the water and the rest of your garden. Planting more trees and other larger perennial plants is always a good idea to reduce waterlogging and surface flooding. Thirsty trees like alder and willow are good choices. They will "drink up" water from the soil, reducing the chances of saturation. Trees increase water storage capacity and improve soil drainage. 

trees along riverbank in the Netherlands
Trees line a small canal in the Netherlands.

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6. Keep Soil Healthy, Covered, and Rich in Organic Matter

Good soil health is crucial for preventing flooding and waterlogging in your garden. In areas with heavier clay soils, add plenty of organic matter to improve soil structure. Mulch well with a good layer of organic material to improve drainage and water storage capacity. 

As with so many challenges in lanscaping, diverse plants and healthy soil are key to preparing for and preventing flooding in your garden.