flooding in gardens How to reduce flood damage in the garden

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1 This leaflet was produced by the Environment Agency working with BBC Gardeners World Magazine Call Floodline now on or visit Environment Agency Floodline Environment Agency Floodline Minicom Service Environment Agency Customer Services Line Website: flooding in gardens Environment first: This publication is printed on paper made from 100 per cent previously used waste. By-products from making the pulp and paper are used for composting and fertiliser, for making cement and for generating energy. How to reduce flood damage in the garden GEHO0405BIZQ-E-P

2 Introduction Contents Flooding can be devastating. The images of flooded towns, villages and communities on our television screens have become all too familiar. Those once in a lifetime floods appear to be happening more frequently and thousands of home owners are facing up to the reality that flooding is a serious threat. While much is being done to reduce the risk, floods can never be prevented. Butwe can prepare for them. This guide offers practical advice on planning, planting and preparing your garden to withstand flooding, so that if the unthinkable happens any damage will be kept to a minimum. It also provides tips and advice on restoring your garden after a flood. By acting now both you and your garden will be better prepared. Enjoy your garden! Adam Pasco Editor BBC Gardeners' World Magazine Planning your garden Improving drainage 02 Raised beds 02 Bog gardens 02 Fences and hedges 03 Paths and patios 03 Electricity 03 Decking 03 The soil 04 Lawns 04 Choosing the right plants Trees 05 Shrubs 05 Perennials 06 Bog garden 06 Soft fruit and vegetables 07 Plants to avoid 07 Preparing for a flood Beforehand 08 When the waters are rising 09 Clearing up the mess Before you start 11 Health risks 11 Buildings and walls 11 The garden 12 Restoring your garden Fences and pergolas 13 Soil and borders 13 Ponds 13 Containers 14 Lawns 14 Shrubs and perennials 14 Vegetables 14 Environment Agency BBC Gardeners World 01

3 Planning your garden Improving drainage Most people with gardens on heavy soil have problems with drainage, and it's made worse if the water table (the natural level of groundwater in the soil) is high, because the ground has little capacity to absorb heavy rain. You can't do much about the water table, but if it's low enough, you can install land drains. These are clay or perforated plastic pipes laid in gravel and connected to a soakaway or pit. Water collected there slowly drains away naturally or can be pumped into a ditch. Soakaways are best positioned in the lowest part of the garden at least 5m away from buildings, and dug about 1.8m deep (but above the water table). If you decide to put in land drains, check with the local authority before starting work to find out whether water can be piped into the drains. If your garden regularly floods after heavy rainfall, one solution is to set a narrow drainage channel along a garden path or border, connected to the storm drain underground. Slow drainage is sometimes just caused by a compacted pan of soil below ground level. It may need breaking up to letwater through into lower layers. However, don't be too enthusiastic if you have sandy or chalky soil, as it can dry out very quickly. Raised beds For plants or vegetables that cannot cope with water logging, building raised beds is a good solution. It keeps the roots out of water and helps the soil warm up more quickly in spring. Try edging them with boards, concrete blocks or timber sleepers. Substantial raised beds need drainage, so remember to leave "weep-holes" a little above ground level and make sure the soil mixture you use to fill the beds contains plenty of grit and compost. Bog gardens You may prefer to work with nature by creating a bog garden or pond. Either will help drain the surrounding soil. A pond can be planted with water plants and both can be surrounded with a wide variety of bog plants such as hostas and primulas. These will put on a lush display of foliage and flowers, and if well looked after, should be perfectly happy in drier spells too. For a suggested list of suitable plants see page 06. Fences and hedges If you are replacing fencing in a floodprone area, consider more waterproof alternatives, such as concrete posts or gravel boards. The concrete can be painted with exterior masonry paint to blend in. Hedging and arbours can be made from living willow, which is virtually flood proof, easy to grow in damp areas and looks attractive all year. Paths and patios Gravel, bark and light materials are likely to be washed away by flooding. Stone, bricks or paving slabs are more durable, but can be very slippery under water and after a flood, so specify a rough finish. Bark chippings make good temporary paths over recently flooded ground. Avoid covering large areas with paving if possible, as hard surfaces reduce the area where floodwater can drain naturally and maycontribute to flooding elsewhere. If you do need to lay paving, choose small slabs, brick pavers or blocks laid on sharp sand, so that water can drain through the gaps between them. Electricity Water and electricity don't mix. Legally, all electrical work must be carried out by a qualified electrician, so never attempt this yourself. Make sure the mains supply to your garden is protected by a residual current circuit breaker. An isolating switch inside the house is necessary so that power to the garden can be immediately disconnected if necessary. Decking Decking is fashionable at present, and has obvious value in raising the walking surface above ground. Check out the Timber Decking Association's web site at for tips, advice and a list of members. 02 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 03

4 The soil Wet or heavy soil can kill young plants, so soil preparation and planting times are crucial. Wait till the soil warms up in spring before planting, because the cold will keep them dormant and the wetwill probably rot their roots. If you like to grow plants from seed, don't sow them directly into claggy soil. Sow into pots or seed trays before planting out once the weather and soil conditions improve. CHECKLIST Planning your garden Familiarise yourself with the water table beneath your garden and know what the water levels are like at different times of the year. To do this, dig a hole about 60cm or more deep and watch to see at what level water rises. Check with local authorities whether excess water can be piped into drains. Consider laying land drains and soakaways and/or connections to public drains. Consider a bog garden or pond with supply ditches in naturally wet areas. Raise ridges of soil for hedging, and wide beds for flowers and vegetables. Consider paving and decking carefully to improve access. On soggy ground, remember that any hole is liable to fill with water. So before planting, dig over a wide area around the planting site, breaking up the subsoil or clay, and forking in plenty of 3mm grit to improve the drainage under and around the roots. Tease out plant roots and mix some potting compost in with the soil in the planting hole. Planting on a slight mound will help to drain water from vulnerable crowns. Lawns If a waterlogged lawn is a regular problem, stepping stones can help. Spiking over heavy or compacted lawns with a hollow tined aerator or fork and then dressing it with sand will make a small improvement and encourage stronger grass growth. Choosing the right plants If you are planting in a flood-prone area, it is worth choosing plants that can withstand some water logging. Even if there's just one low-lying spot in the garden, selecting plants that enjoy damp soils will reduce casualties and make it an attractive feature. Suggested moisture-loving plants are listed below. Some of them will suffer if the soil does dry out in the summer, so use plenty of rotted plant material when planting and keep them well watered. Trees Few trees, except the large swamp cypress (Taxodium distichum), will thrive with their roots in water for long but several species cope well with damp soil and intermittent soakings, including alder (Alnus), ash (Fraxinus), river birch (Betula nigra), silver birch (B. pendula), hornbeam (Carpinus), rowan (Sorbus aucuparia), willow (Salix) and wing nut (Pterocarya). Shrubs With the possible exception of some willow and dogwood species, most shrubs will deteriorate in constantly boggy ground. However, many grow well on moist soil provided it is not permanently waterlogged. This selection of shrubs will tolerate damp soil conditions and should withstand the effects of occasional short-term flooding: Common name Latin name Snowy mespilus Amelanchier lamarckii Red chokeberry Aronia arbutifolia Sweet pepper bush Clethra alnifolia Dogwood Cornus varieties Bog myrtle Myrica gale Ninebark Physocarpus opulifolius Willow Salix varieties Elder Sambucus varieties Bridal wreath Spiraea x vanhouttei Snowberry Symphoricarpos Guelder rose Viburnum opulus Always employ an electrician to carry out any electrical work. 04 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 05

5 Perennials These perennial plants all tolerate damp soil conditions, and should withstand the effects of occasional short-term flooding: Common name Latin name Goat's beard Aruncus dioicus Astilbe Astilbe Elephants' ears Bergenia Kingcup Caltha palustris Campanula Campanula lactiflora Sedge Carex Bugbane Cimicifuga Cirsium Cirsium rivulare Joe Pye weed Eupatorium purpureum Spurge Euphorbia griffitthii and others Filipendula Filipendula purpurea Willow gentian Gentiana asclepiadea Cranesbill Geranium Water avens Geum rivale Giant rhubarb Gunnera manicata Sneezewort Helenium autumnale Day lily Hemerocallis Plantain lily Hosta The bog garden Here's a selection especially suited to a bog garden: Common name Bugle Lady s smock Meadowsweet Water avens Ragged robin Purple loosestrife Water mint Globe flower Latin name Ajuga reptans Cardamine pratensis Filipendula ulmaria Geum rivale Lychnia flos-cuculi Lythrum salicaria Mentha aquatica Trollius europaeus Houttuynia Houttuynia cordata Inula Inula Siberian iris Iris sibirica Ligularia Ligularia przewalskii Cardinal flower Lobelia cardinalis Maltese cross Lychnis chalcedonica Yellow loosestrife Lysimachia Purple loosestrife Lythrum salicaria Monkey flower Mimulus Miscanthus Miscanthus Water forget-me-not Myosotis spp Royalfern Osmunda regalis Bistort Persicaria New Zealand flax Phormium tenax Primrose Primula Ornamental rhubarb Rheum Rodgersia Rodgersia Meadow rue Thalictrum Violet Viola Colour Blue Lilac Cream Deep pink Pink Purple Pink Yellow Flowering period April-June April June-July April-June May June-August July-September May Soft fruit and vegetables Planting on a mound can help shallowrooting plants such as raspberries and strawberries to survive water logging, butmulch them well in spring to counteract the drying effect of the mound in hot weather. Raised beds also CHECKLIST Choosing the right plants suit vegetables, but crops that need to overwinter or any vegetables that need good drainage throughout their growing season are probably best avoided. Plants to avoid Cherries and beech are vulnerable to flooding, as are Forsythia, Cistus and Genista (broom). As a general rule, plants which tolerate drought don't like wet soil or being flooded. Many herbs and subshrubs from Mediterranean climates, such as thyme, rosemary and lavender, and bulbs which originate from dry areas, such as tulips, are also vulnerable. These plants are best grown in pots or raised beds. Don't try to work the soil when it's cold and wet. Wait for warmer, dryer conditions. Break up the sub-soil, digging in plenty of grit and compost. Fork over the remainder, leaving drainage channels round precious plants. Spike the lawn, and fill holes with grit. Plant soft fruit, asparagus etc on raised beds. Avoid over-wintering root vegetables. Choose plants that will withstand or enjoy wet conditions. 06 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 07

6 Preparing for a flood Climate change will lead to more extreme weather and more frequent floods in the future. Although flooding is a natural event that can t be prevented, you can prepare for it and take measures to reduce its impact on your life and property. Beforehand Find out if you are at risk of flooding and details of how to receive flood warnings by calling the Environment Agency s 24 hour Floodline , or visit the Environment Agency s website at Check your building and home contents insurance policies to see exactly what cover you have for flood damage to the garden. Insurers usually pay for damage to outbuildings, garages and sheds, but not to gates, fences, hedges, garden plants, containers or ornaments. These normally require an extension to your household policy. Take photographs to record valuable possessions such as lawnmowers and garden tools. If you are not inoculated against tetanus, contact your local doctor or health centre. Keep supplies to hand e.g. a shovel, saw, hammer, nails, a stock of unfilled hessian or plastic sandbags, sand, bricks, or sheets of plywood. The sandbags can be used to weigh down garden structures and shore up weak/damaged banks and retaining walls. In an emergency, old pillowcases, empty compost bags or black plastic sacks can double as sandbags, and they can be filled with earth as well as sand. Don't overfill the bags, and take care when lifting. Be ready to protect large areas of sheet glass in patio doors or greenhouses from fast-flowing water and debris using the wood. Move treasured border plants to raised beds, or pot them up and move to somewhere safe. Check that non-return valves are fitted on outdoor taps. When water levels are rising outside Unplug all exterior electrical equipment such as lighting, pond pumps and filters. Turn off the water supply to the garden. Weigh down manhole covers with sandbags or heavy objects. Floodwater can move them as it flows out and these open holes are dangerous. Move free-standing items such as pots, dustbins, compost bins and furniture to a sheltered, higher spot, or weigh them down with sandbags. Tie in climbing plants, and check the ties on newly planted trees are secure. Anchor fruit cages against storm damage and, if time permits, dismantle cold frames and cloches. Peg netting securely over ponds to save plants from being swept away; fish will often stay in their ponds, but it's probably safest to net valuable specimens and keep them in large buckets or tanks on higher ground. Move animals to a safe area. When water levels are rising the shed and greenhouse Lift heaters, grow-lights, pots and compost well out of harm's way. Close the valves on gas cylinders and unplug all electrical equipment. Take valuable items, tools, powered machinery (and related paperwork) indoors where practical or raise it on pallets. Lock gardening tools away. Empty the fuel tanks of powered tools. Take petrol, chemicals, fertilisers, pesticides and paints and lock them away indoors. If left outside, they could cause pollution and be wasted. Close greenhouse doors and vents, and make sure the structure is anchored securely into the ground or onto a concrete base. Harvest any crops that can be ripened indoors, such as tomatoes. 08 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 09

7 Clearing up the mess CHECKLIST Preparing for a flood Know what your insurance covers, and what it doesn't. Keep a camera handy to record any damage. Check your tetanus jabs are up-to-date. Keep a supply of timber, plywood, nails, sandbags and sand. Move valuable pots and plants out of harm's way. Disconnect all outside electrical installations. Peg netting over ponds, move livestock to safety. Move fuel, paint and other chemicals to safety. Board up vulnerable glass in doors and greenhouses. Before you start Water levels can fluctuate, so check weather reports and call Floodline for the latest flood warning information. Don't start repairs until you are sure that the floods are over. If you expect to make an insurance claim, do not throw anything away until you have been told that you may. Photographs will be invaluable to record the damage. Mark the high water level on outside walls for reference. This will also act as a reminder when replanting the garden. Health risks The floodwater is likely to be polluted with oil, chemicals and untreated sewage, so wear rubber boots and gloves when working outside, and cover any open wounds with waterproof plasters. Although the risk of illness is minimal, if you accidentally swallow floodwater and feel unwell, contact your doctor. Young children, pregnant women, the elderly and anyone with a weakened immune system should avoid contact with the water. Avoid walking through floodwater. Fastflowing water or deep still water can be dangerous, and be aware that the mud is likely to conceal broken glass or lumps of debris even in your garden. Move slowly and carefully and use a stick to check for holes, dislodged manhole covers and sharp objects. Buildings and walls The mud, algae and moss can be washed off walls with a powerful hose, and if necessary the use of disinfectant and chemical path cleaners. Remember to clear the area around all the airbricks to let the air circulate again. It's advisable to examine your roof, walls, fencing, doors and windows as soon as practical for any damage or changes. Cracking and buckling may have occurred sufficient to weaken a wall and you may need to get a professional assessment and repair by a reliable contractor. Brick or block walls will gradually dry out naturally, but old brickwork may be damaged by the pressure of the floodwater. Keep an eye open for any 10 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 11

8 new cracks, then once the brick has completely dried out, fill them and repoint the joints. Be careful if a lot of mud or silt has piled up on both sides of a wall. To keep the pressure on it roughly equal, clear the mud gradually from both sides. Clearing one side at a time could damage it. The garden Do not restore electricity to the garden or use any appliance that has been affected until they have all been checked out by a qualified electrician. CHECKLIST Cleaning up the mess Don't start repairs or throw anything away until floods have gone and insurers have been informed. Call Floodline for the latest flood warning information. Wear boots and rubber gloves when working outside. Keep children, pets and vulnerable adults indoors. Disposing of the waste can be a problem. Flood debris is classified as controlled waste because it may contain pollutants, so first contact your local authority. Some will provide skips for the purpose, or can give advice on where to get them. Otherwise, specialist waste management firms can help. Wet sandbags, affected bags of compost and fertiliser, sand from children s sand pits and bark chippings covering play areas should also be disposed of. Drains and gutters will need to be cleared of mud and leaves before the next downpour. Avoid walking through floodwater. There may be open manholes, broken glass or other hazards hidden underneath. Check all structures for damage. Take care when removing debris and silt. Do not switch on electricity until you re sure it's safe to do so. Contact local authority about waste disposal. Restoring your garden If a flood has wreaked havoc in your garden, planting up a few pots with new stock will give you something to enjoy and lift your spirits while you tackle what needs to be done. Fences and pergolas Fences, pergolas and other wooden structures can be damaged by prolonged contact with water. So check for loose posts, panels and breakage. In greenhouses and outbuildings, leave doors and windows open to speed up drying out. Inside, damaged or diseased pot plants should be destroyed, and the glass and benches washed down with disinfectant. Wooden furniture and play equipment will also need checking over, washing down and treating with a fungal inhibitor. Soil and borders If the soil stays wet for a long time, it can lead to shallow rooting and fungal diseases that kill roots altogether. Deep double-digging may help once the soil dries out, but in the mean time, don't go down further than a spade's depth to create drainage channels. Don't tread directly on sodden soil or you will compact it. So work from boards, stepping stones or paths made from bark chippings. You will probably find numerous new weeds appearing when the flooddispersed seed begins to germinate. Hoe them off quickly and spread a thick layer of bark to stop them reappearing. Ponds In general, most aquatic life can cope with freshwater flooding. You may well find that fish have not swum away, but remained in their flooded pond, 12 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 13

9 surviving strong currents by burrowing into the mud. Most aquatic plants, too, are dormant in autumn and winter, and should recover by the following spring even if swamped by sea water. Sea water, however, will kill freshwater fish. Containers Pots and containers that have flooded should be raised onto bricks or wooden pallets to let the water drain away. The top 5-8cm of compost should be removed and replaced with fresh compost mixed with grit or perlite to improve drainage. Lawns Stay off sodden lawns until you can walk on them without leaving wet footprints. If they've been submerged for over a week or are covered with more than two or three centimetres of silt, you need to face the possibility that they will have to be remade. But remove the silt first, and if the flood occurred after September (October in milder districts), wait until March to attempt any major lawn repairs. Shrubs and perennials Most plants will survive a few days immersion in water, but the roots need oxygen and will begin to die if left in cold, waterlogged soil. It may therefore pay to attempt to rescue the most valuable plants. Using a fork, dig them up, wash away the silt and debris, then plant them in a drier part of the garden, or in pots with fresh compost. In other cases, digging a shallow trench round them will help drain water away from their crowns. Lightly breaking up the compacted surface under trees and bigger shrubs will improve drainage. If there are already signs of dieback, check by removing a sliver of bark. On living stems, the bark will be firm, the underside green. On dead stems, the bark will either be soft and shiny, or dry and tough and the underside will be brown or black. Remove dead branches and once new growth develops, give the plant a liquid feed. Soil organisms such as worms may also have been drowned or washed away, so dig in plenty of compost, well-rotted manure or composted grass clippings to encourage them back. Vegetables As a precaution, throw away any vegetable crops that have been covered by floodwater, and remove silt and other debris in case it is contaminated. Let weeds germinate as this will help to dry out the soil, then dig them in before they flower. CHECKLIST Restoring your garden In the greenhouse, wash down glass, staging and other structures with disinfectant. Destroy affected produce. Dig drainage channels to speed drying out. If valued plants are at risk, lift them, wash roots and replant. Stay off sodden lawns. When drier, clear off silt and re-sow where necessary. Check valuable shrubs. Clear silt away, drain off water, and feed when growth restarts. Destroy affected vegetable crops. Let weeds germinate, and then dig them in. 14 Environment Agency BBC Gardeners World Environment Agency BBC Gardeners World 15

10 It is the Environment Agency s job to look after your environment and make it a better place for you, and for future generations. Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier. BBC Gardeners' World Magazine is Britain's biggest selling gardening magazine, providing fresh ideas and clear advice for thousands of gardeners every month. Its innovative approach to gardening offers creative, practical and problem-solving solutions to gardeners throughout the country. With regular features by the best names in BBC gardening, like Monty Don, Alan Titchmarsh, Carol Klein and the Gardeners' Question Time team, BBC Gardeners' World Magazine offers authoritative, trustworthy advice on all areas of gardening. From plants and flowers to gardens and design, allotments and kitchen gardens to shopping guides and tried and tested reviews, Gardeners' World Magazine has become Britain's most respected gardening publication. The Environment Agency builds and maintains the majority of flood defences in low-lying areas of England and Wales, to reduce the risk to homes and businesses. We are also responsible for warning the public about flooding from rivers and the sea in England and Wales and raising awareness of flood risk. The Environment Agency. Out there, making your environment a better place. Floodline Special subscription offer To make the most of your garden, take out a subscription to Gardeners' World Magazine and save 15% - 12 issues for only 30. Call BBC Gardeners World now on quoting reference GWENV05 (Offer ends 31 Dec 2010 and is available for UK delivery only). 16 Environment Agency BBC Gardeners World