Garden Design (2015)

Managing water

Rainwater from buildings and structures is stored in interconnected tanks in this rain garden, helping to prevent flash flooding and providing a habitat for aquatic plants and wildlife.

KEY TO PLANTS’ WELLBEING, water is critical to any planted scheme, so take action to ensure this precious resource does not simply go down the drain.

WATER WISDOM

Of all precious resources that can be harvested, rain water is probably the most squandered. While rainfall replenishes soil moisture and provides humidity to keep plants hydrated, in towns and cities most simply goes down the drain. In addition, urbanisation has greatly increased the area covered by impermeable surfaces, so that intense rainfall quickly overloads drains and sewers, causing flash flooding. With rainfall patterns predicted to become more intense and urban living expanding rapidly, the situation is set to become worse unless these issues are addressed. We can all help to reduce the problem by limiting the amount of impervious hard surfacing in our gardens, particularly in front gardens used for parking cars. Permeable materials, such as gravel and unjointed paving, will help storm water percolate away, while planted beds also soak up excesses. In addition, rainwater collected in butts or underground tanks not only supplies irrigation for plants and replenishes ponds and water features, it can also fill toilet systems and run other domestic systems in the house. Water collection can be simple or sophisticated, and may include pumps, purification equipment and drip-irrigation systems.

RAIN GARDENS

Gardens or parts of the garden that act as a sump or reservoir for the temporary storage of storm water are known as ‘rain gardens’. They are already familiar features in areas of the world that experience regular storm events, as they enable excess water to slowly discharge, evening out the flow into drains and sewers and preventing flash flooding. With the increasing uncertainly of weather patterns, these gardens are now being included in more temperate parts of the world too. As well as alleviating flooding, rain gardens bring additional benefits, supporting wildlife by providing refuges for amphibians such as frogs and newts, as well as drinking and bathing water for small animals and birds. They can be beautiful features, too, supporting a host of ornamental marshland and bog plants.

To create a rain garden, you will need to consider a number of factors, including where the rain will be diverted from, such as the roof of a shed, summerhouse or garage, and where best to site the sump area. If attempting a large scheme, where water is taken from the house roof for example, check the capacity and siting of the sump required with a qualified engineer or ask an experienced practitioner for advice before you begin.

A small rain garden in a domestic plot collects water from a summerhouse roof and overflows into a soakaway in front of the patio.

Water butts offer a good way of storing rainwater from garden buildings. Larger volumes can be stored in underground tanks and used when the butts run dry.

Gravel surfaces allow rain to percolate slowly into the ground, rather than run into the drains. A purpose-made mesh grid holds the gravel in place, even in areas of high traffic such as driveways.

Heavy gauge metal tracks provide vehicular access to a front garden, while groundcover planting and gravel collect rainwater and allow it to soak away naturally into the ground.