Monday, 16 November 2015

Autumn 2015

Last summer we went to Brittany. At some point in our stay I remembered that beavers had been returned to Brittany in the 1960s. We drove towards the catchment of the Elez and found this sign near a lake. Freshwater pearl mussels and beavers! I had always thought the two species must coincide, not least because Peter Goodwin told me that he had seen banks of freshwater pearl mussels near beaver dams while on visits to the USA.

Now we return to November in Perthshire.

This is the famous top dam downstream of the drive at Bamff after the recent heavy rains.

Ambitious? Not really - it's just a willow.

This is part of a new complex of dams in the burn below the old and ruined gamekeeper's cottage at the Burnishead.

Monday, 7 September 2015

An Indian Summer?

On the way to the Wet Wood, a pool dammed by some reed sweet grass.

The simplestem bur reed has spread remarkably into the Wet Wood and down the Burnished Burn to flourish along its reaches. Jeremy Purseglove mentions the plant as an important one for wetland habitats in his 'Taming the Flood', first published around 1986 and republished with revisions and beautiful woodcuts this year. 

Summertime, a short spell of drought, and the canal is running more as a trickle than an engineering work along which branches may be floated.

Overall the work of the beavers has made the whole place wetter. My leaky trainer shoes confirmed this for me, though the undergrowth was too thick to see through.

The arrival of a hobby was an excitement of the summer at Bamff. Hobbies tend to be further south. They prey on fast birds such as swifts and swallows, but also dragonflies. Could an abundance of dragonflies at Bamff encourage them? I don't know, but swallows, martins and bats looking for invertebrate life over the ponds could well.

Friday, 21 August 2015

I Missed the Deadline for September's 'Alyth Voice'.

There you go. There is no latitude on the deadline even for the editor of 'The Alyth Voice'.

The Sting and the Buzz

I have taken to standing and waiting for the green figure to replace the red one at pedestrian crossings with traffic lights. It gives one a moment to stand and stare. As the Welsh poet WH Davies put it:

What is this life if, full of care,
We have no time to stand and stare.
No time to stand beneath the boughs
And stare as long as sheep or cows.
No time to see, when woods we pass,
Where squirrels hide their nuts in grass.
No time to see, in broad daylight,
Streams full of stars, like skies at night.
No time to turn at Beauty's glance,
And watch her feet, how they can dance.
No time to wait till her mouth can
Enrich that smile her eyes began.
A poor life this if, full of care,
We have no time to stand and stare.

It was just at this moment, while waiting for permission to cross the road that I heard the sound of an angry group of herring gulls. Looking up from the display of pumpkins on the other side of the road, I saw a group of gulls, a regular hue and cry, chasing a buzzard. Well, I would not have been surprised at home, but this was Edinburgh.

Here we are in Edinburgh for a few days: going to the Festival and its Fringe, walking about, reading and writing. I love Edinburgh during the Festival. I like to see all the people going about, hearing all the different languages and the discussions. What of the performances? The Marriage of Figaro, performed by the Budapest Opera was a delight. I have been haunted by magical memories of the music for the last three days.

As to reading, I have just finished ‘A Buzz in the Meadow’ by Dave Goulson. Until a year or two ago, he was Professor of Biology at Stirling University (since moved to take up a chair at Sussex University). I wandered through his department once, while lost in a maze of corridors, looking for another Dave (Dave Gilvear, a professor of fluvial geomorphology). The walls were adorned with beautiful photographs of bumble bees. Back home again, and on to the internet, I discovered the Bumblebee Conservation Trust, a charity Dave Goulson set up while at Stirling University to promote their conservation. 

Bumblebee numbers are declining: thirteen species became extinct in at least one country in Europe between 1950 and 2000. Why? The usual reasons are given: loss of habitat due to agricultural intensification, urban development and disease. Last year Goulson’s book ‘A Sting in the Tail’ was published to great acclaim. An interesting section describes the dependence of soft fruit growers in Strathmore on wild bumble bees to pollinate crops of raspberries and strawberries while at the same time buying in commercially reared bumblebees. The worry is that centrally reared bumble bees may be the bearers of disease to the native wild populations. 

This year Goulson has followed up his earlier success with ‘A Buzz in the Meadow’, another excellent and readable, but alarming work in which, among a great deal else, he describes his research on the effects of the neonicotinoid insecticides on bumblebees and their part in the Colony Collapse Disorder that so worries the keepers of honeybees. 

When they were first introduced in the 1980s the neonicotinoids were seen as  reassuring successors to the organochlorines (DDT.Dieldrin, etc.) of the 1950s-1970s, and the organ-phosphorus compounds of the 1980s to 90s. The neonics, as they are called for convenience, are very poisonous to insects, but less so to mammals, which has to be a good thing. Since the late 1990s, however, there has been increasing concern about their environmental impacts. Like the organochlorines they build up in the soil and can linger on in sediments under water. They cause initially subtle, but real damage to the nervous systems of bees. The worrying thing is that these pesticides are very widely used: as seed dressings for cereals and oil seed rape, and as sprays for soft fruit. Being systemic they penetrate right through the plant, making the whole thing poisonous to insects. This is fine if the insects are pests, but disastrous if the species affected include bees, and the other insect pollinators that enable us to continue to live on this planet.
Did the light go green? 

STV's Nature Nuts with Julian Clary went down very well. The filming that happened here took place last year some time, I think. Bob Smith took the part of paddler of the canoe

This is the 'High Dam' in full flow, taken about the 8th August.

Now we have a team from the RSPB filming beavers here. I am looking forward to seeing the results of their work.

Sunday, 26 July 2015

The Alyth Flood, 17th July and afterwards.

Much has already been written about the flood of 17th July and its aftermath, and I am going to add to it. An important aspect for those of us who are interested in the official restoration of the beaver to Scotland is the concerted attack on the species by interests hostile to their return.

Peter Grewar Jr. seems to have begun the campaign. He visited Alyth on the 17th and drove up to Bamff where he noted that some rough grazing had rushes growing in it that indicated poor drainage.

High water table indicates that there is little capacity for the soil to take more water: a reasonable point of itself, but what he missed was that although that field is a wet field it is not always so, at least not in summer, generally speaking, when there is a water deficit for at least some of the time. Ewan Pate in his article in the 'Courier' last week spoke heavily and portentously about poorly drained land and those who own it.

Why would you drain generally wet land if there is no significant profit to be had if you did? Besides what beaver dams achieve is to spread the water, so taking the energy out of the flood - leaving aside the important filtering functions: the removal of surplus nitrates, phosphates that are such a problem in the diffusely polluted waters of lowland Strathmore. And then again there is the biodiversity of wetlands.

Originally Peter Grewar Jr. claimed that logs and branches in the debris that lodged in Alyth were the work of beavers. A tree still in the Den of Alyth, upstream from the town had the marks of beavers on its barked trunk, he had been told. Our friend, John Ferguson, who helped clear the Alyth Burn of debris  told me that he had seen no examples of timber that had been gnawed by beavers.

Here is a tree that was photographed and the barked bits of the trunk described as having been stripped by beavers. In fact the bark must have been stripped off the tree as it was washed down the Alyth Burn and rubbed against rocks on the river bed, or other detritus. I could see no signs of beaver tooth marks on this tree or any of the others I walked by.

'Na craobhan mòr, miarach,
As am friamhaich 'gan reubadh.

The big branchy trees,
Ripped from their roots. (Gaelic song)

But what if there were? The area of the beaver ponds at Bamff amounts to about a hectare. Taking into account the rest of this mini catchment of perhaps up to five hectares, you have to remember that the whole Alyth Catchment amounts to 3600 hectares. If we take the outside figure of five out of 3600 hectares that is 0.001 of the catchment. Water did run over the barrage that closes the ponds at Bamff, but did not break it, or any of the other dams at Bamff that are part of the Alyth catchment.

The blame game started by a few people spread with the help of one Alex Stoddart of the Scottish Countryside Sports campaign. This group seems to be a subsidiary of the Scottish Gamekeepers' Association.  'The Courier' published an interview with him in which he spouted all sorts of nonsense. This nonsense was published in 'The Scotsman' and 'Herald' as well. Much of the same article found its way into the 'Sunday Express'. It is true to say that I was quoted giving a response to Stoddart's assertions. 

In the meantime opinion in Alyth itself had focussed on the management of the Alyth Den, a riparian woodland, managed by Perth and Kinross Council for recreation. Over the years paths have been made, some building up of the river bank carried out, and a large concrete sluice installed, as well as a foot bridge. The foot bridge was built in 1990 by the Aberdeen University Officers' Training Corps. Solidly built of two massive steel girders, set in concrete, the bridge survived.

The criticism of Perth and Kinross Council was based on the fact that substantial amounts of chain saw cut logs had been present in the debris that carried away the two foot bridges and had come to rest against the bridge in the Market Square.

Given the force of the flood, already washing away farm roads as far away as Craighead of Bamff, I wonder how relevant the logs from the Den were. 

Built up bank with downstream banks swept away.

The bridge built by Aberdeen University OTC.

A large sluice close to the town of Alyth from downstream side.

The same sluice from upstream with some debris still present. Did this block early in the incident, get torn away by a build up of more debris and contribute to the second pulse of flooding of which people speak?

The severity of the rainfall of the night of 16/17 July had been predicted by the UK Met Office.

Here are two photos of one of the dams near the drive at Bamff before and after the 17th July



Alan Law, part of whose study area for his PhD about beavers and their ecology was at Bamff, tweeted.

This graph is taken from his research.

This photo shows the Wet Wood, which is on a mini catchment that flows via the Auchrannie Burn into the Isla and so misses out Alyth, late in June when there had been a spell of dry weather. Some water did remain in a channel immediately next to the dam (the Long Dam), but otherwise the area was very dry.

Recent years have seen the arrival and tremendous expansion of water bur reed (Sparganium erectum) and sedges.

This photo and the ones below show the area after the 17th, now once again full of water. 

A beaver kit explores its surroundings at Bamff

Here is my piece for August's number of 'The Alyth Voice'

The Flood

A wall of water thundered down the burn: within a few hours the Market Square of Alyth lay four feet deep in it. Cars parked along Commercial Street were shunted onto each other like so many copulating beetles. John Ferguson rescued a lady caught in her car. The occupants of a hundred houses had to be offered accommodation as their homes flooded. Massive amounts of woody debris, including large bits of tree trunk had smashed the two foot bridges. Some came to rest in the arch of the main bridge that spans the burn, as did a skip, while the rest sped on. A sheep washed by, struggling on the chaotic waters. Luckily the old pack horse bridge survived. 

A downpour of unprecedented proportions had struck Alyth. The Meteorological Office has been warning us for some years that the kind of flash flood that results from such an event is to be expected as a feature of climate change. But why Alyth, we ask ourselves? There is no answer to that, but to say that Alyth is not alone: think of Bankfoot, Pittodrie in Aberdeenshire, even the Open at St.Andrews. These may be random strikes that come with little warning. A forecast of ‘heavy rain’ doesn’t imply massive flooding, after all: or does it? 

The flood itself was relatively short-lived. By mid-day on Saturday 18th July, a visitor to the Market Square, would hardly have known that a serious inundation had taken place, except that clearing up was continuing and the high visibility jackets of the SSE people were prominent. Driving home from Edinburgh, we could see flood waters gathered around the confluence of the Isla and the Ericht.

In the meantime those affected by the flood had been offered temporary accommodation and food and clothes provided. The community of Alyth had pulled together tremendously and with characteristic generosity, I learned, but the repairs to homes and property will take a long time to achieve. Some damage may prove to be irreparable.

Flash floods happen in a context. The Alyth Burn rises high up in the Forest of Alyth, way back near the watershed, north of Drumderg. It flows through this bowl of land, joined by the Ollies Burn in the den south of Tullymurdoch and to the west of Gauldswell. The dens that receive the runoff from the open hills concentrate the flow: a cloudburst in the hills must lead to flooding below. This is what happened on the night of Thursday/Friday, 17th July. The rush of water uprooted trees, smashed fences and dykes, carrying with it water gates from the Mains of Creuchies as it flowed past on its way to Alyth. At Mill of Fyal water from the Welton Den, the Bruckly Burn and Bamff (and yes, water from the overtopped beaver ponds, too), joined the wall of water, gathering momentum on its way through the Alyth Den and so to and through the town.

When Alyth grew out of the old town that ran along today’s High Street into the low boggy ground below, the burn was effectively turned into a canal, and the drained haugh next to it built over. As a result, for the last two hundred years or so, the water has not had the former flood plain into which to overflow and lose energy. This is no comfort to those whose homes and shops have been damaged in the latest flood, but it may be an opportunity to consider aspects of flood and catchment management that have eluded us so far, but need to be resolved in this time of climate change, so that people in Alyth can live reassured.

The problem for Alyth as a flood prone place does not lie so much in the Den as in the hinterland. The open hill grazings and the ploughed coniferous plantations shed water with great speed. The Rivers Isla and Ericht are notorious for the speed with which they rise and fall. There needs to be a good programme of re-afforestation of the hills. Research for the Eddlestone Water project has shown that soils under old broadleaved woods are ten to fifteen times more permeable than are soils under coniferous plantations or hill grazings. It is time we took notice of this kind of research and acted. 
Will this kind of flood, relatively infrequent until now become a 30 year event? What will insurers think of that? Perhaps flood prone, flood plain settlements will have to move to higher ground?

The press reaction fails to credit the Alyth folk with their intelligent and compassionate reaction as they set about recovering from the shock of the flooding.

Very few believed that the beavers had any part in the floods: in fact the idea of beavers with chainsaws has become a joke.

Tuesday, 20 January 2015

January 2015 - Dippers and Other Matters

This is my piece for February's number of the Alyth Voice.

Dippers in the Burn

Standing for a moment before joining the queue for the checkout in the Co-op, I looked through the magazines on the periodicals stand. I noted 'Horse and Hound', 'the Scottish Farmer' and sundry others, many with pretty cover girls: I decided that I liked a lovely brunette best, and then my eye lit on 'The Scots Magazine'. Now, I had been meaning to buy the current number because I noticed somewhere recently that Jim Crumley had an article about beavers in it. I took a copy from the shelf and looked for the piece in question. Well, there it was and blow me down if he hadn't written about the very same subject that I had chosen to write about in February’s ‘Voice’! In short, Jim's article in 'The Scots Magazine' is as much about dippers as it is about beavers: and why not? Here is what I wrote, but I should like to recommend Crumley's excellent piece in January's 'Scots Magazine' to you.

The dipper is a delightful bird. For a while I have been able to watch one going about its business along the Burnieshed Burn here at Bamff. The first I know of its presence as I walk along the path is the song,  melodious, but slightly harsh. I stop and stand, wondering when the bird will reveal itself to me. It is going to be hard to make out in the snow blotched landscape. Perhaps it will show itself by taking off and flying swiftly along the burn to some other stance, where it will look out for things to eat, or it will give itself away by bobbing up and down and displaying its white front? Today, it was the latter. All of a sudden I realised that a white patch on the other side of the burn was the dipper. I watched to see what the bird would do. At one moment it jumped into the water and splashed around for a while. I hoped to see what it had caught, if anything, but could see nothing. It emerged from the water and went back to its stance. Dippers favour streams with fast flowing water and gravelly beds. Their diet consists mainly of the larvae of mayflies and caddis flies and other insects, as well as some fish eggs and very small fish. I watched for some moments and took a few photographs before moving on into the wood. The exciting thing about the colonisation of the Burnieshed burn by dippers (and the visit last autumn of a kingfisher) is that it is evidence of the increasing productivity of the burn and its capacity to maintain populations of birds, fish and mammals, having been until eight years ago no more than a narrow ditch, and seasonal destination in the years past of breeding sea trout.

The harder weather of the last few days has brought in the snipe. Out for a walk at dusk, I disturbed several of the birds. They zigzagged into the sky, crying ‘Grit, grit!’ Three mallard quacked their way off the flooded land as I continued on my way, slithering cautiously over the refrozen patches of ice. Over the fence at the end of the field, I climbed up the bank and on to the farm road, then down the other side and over another fence into the West Wards. The burn is running full and the water level in the wet wood beyond is as high as I have seen it. The neatly cut canals are flowing and paths to felled trees show that the beavers are active. Having completed my circuit I headed for the warm glow of the kitchen windows and a cup of tea.

Wednesday, 10 December 2014

Here is the dam referred to by Alastair Driver in a recent post on Twitter. It breached on the 7th November and has been repaired since then. The V-shape is a triumph because the water flowed through the gap it now blocks with tremendous force after the nearer part of the dam was rebuilt. 

You may notice that rhododendron has been used in the rebuilding. It sometimes looks as though the beavers were just using it as an adornment to their more serious work. 

I took this photograph yesterday. You can see there is a bit of frost on the ground.

The fine dam down the drive collapsed after heavy rainfall about a fortnight ago. 

Interestingly, the beavers who live in the burrow above the site of the dam have done nothing about it so far. Have they left the burrow, or are they content to leave repair work for the time being?

There are troubling reports of the destruction of riparian woodland up and down the Dean Water and as far afield as Weem. 

This photograph shows a ditch at Weem. The bankside vegetation has been stripped away apparently to discourage the beavers who built that dam.

And in this photo you see the riparian woodland neatly stacked by the water side.

The Swiss Federal Government's Department of the Environment have published a document about beavers and the riparian habitat which puts our compatriots to shame.

The link is:

The text is in French, but the photographs and figures with their captions are self explanatory.

I have made a crude translation, which is best read with the original French document:

Revitalisation of waterways: the beaver is our ally

Revitalising the waters - for and with the beaver

In 2011, a revision of the law on the protection of waters was accompanied among other things by the launching of a permanent programme for the restoration of rivers and streams at local level. The present document shows how the activities of the beaver can be useful for the ecological improvement of aquatic habitats within the framework of the implementation of this programme and how it is possible to avoid conflicts with this rodent. This document is intended for specialists in the federal, cantonal and communal establishments who are competent in the subject, as well as for those in the offices of engineers and environmental consultants.

The updated law on the protection of waters and the corresponding regulations define a minimal space that is reserved as riparian zone. This minimum space depends on the width of the bed (cf fig.1). The area surrounding the watercourse can be used as sacrificial or as extensive meadowland, or be covered with woody plants. These habitats are considered as surfaces for the promotion of biodiversity, giving priority to its contributions. The use of fertiliser and pesticides is not allowed there.

Bringing the riparian landscape to life

The revision of the law has been matched with a programme for the  restoration of embanked water courses that had been straightened or put underground (fig.2). Here are the objectives of restoration:

> high water can be allowed to flow without causing damage.

>waters are not polluted by substances coming from the surrounding area.

>the waters are colonised by a fauna and flora that are characteristic of that water course.

>the terrestrial and aquatic environments form a connected network.

>the landscape is diverse in structure.

So that these objectives can be properly met, the space reserved for waterways must generally speaking be wider than the minimal space cited in the regulation on the protection of waterways. The publication entitled 'Main ideas - Swiss waterways' prepared by several federal departments can serve as reference.

From now to the end of the century it is foreseen that 4000 km of waterway will be restored. It falls to the cantons to designate the rivers and streams concerned. The costs and associated costs will be borne jointly by the Federal authorities and the cantons.

The larger the area reserved for the water course the greater will be the federal subsidy
The total of the federal subsidy granted for a project of restoration will depend essentially on the foreseen size of the space reserved for the waterways. The wider the area, the more will be the contribution of the State to the total cost of the project, from where the least expenses (in absolute numbers) for the canton en depit of extra costs for the purchase of land.

The acquisition of areas of ground necessary for restoration is to be carried out within the framework of a fundamentally integrated improvement with exchange of land.

The loss of farmers’ productive land can be compensated for by improvements to their infrastructure, notably by the regrouping of the farmer's of basic equipment or by the construction of modern infrastructure such as farm roads (Suissemelio et OFAG 2011).

>  The beaver: architect of waterways

The management of water courses is not the prerogative of humankind.The beaver is itself very active in this domain: to the extent that its talents as architect have to be taken into account in the planning and realisation of  projects of riparian restoration.

Beavers are capable of shaping freshwater landscapes to their advantage. No other living creature apart from humankind can do as much. From which comes the following question: how has this rodent developed such an astonishing capacity?

To serve as habitat for a population of beavers, the waters of a stream must flow gently and be a minimum of 50 cm deep, even in times of low flow. In these conditions, beavers can swim easily, transporting branches for their building projects and building up stores of food for the winter (fig.3), dive under the water to avoid danger and to dig into the banks to make burrows whose entrance must always remain submerged.

Such conditions are sufficiently rare nowadays, 15 million years since the genus Castor first made its appearance, because water courses naturally undergo an alternation between low water and flood. When precipitation is heavy, they swell and flow faster. In time of drought and in winter, they attenuate and become a single ribbon of water.

In the course of evolution, the beaver has learned how to render these streams perfectly habitable. In the zone of retention created by the dam he has built, the water level remains constant, the entrance to the burrow is never dry and the speed of the current is considerably reduced.

Its activity as architect is not limited to the building of dams. In order to obtain branches which it needs to carry out its building works and create reserves of food, the beaver strips whole parcels of forest. And to make connections between the little water courses present on its territory, it digs canals.

Certain species have appeared thanks to the beaver

In behaving thus over millions of years, the beaver has created certain habitats in the freshwater landscape that would only have been found occasionally before its intervention: ponds, still waters, marshes, bare sunny clearings in alluvial forests. In this sense the beaver was an essential factor in the evolutionary process. Certain species of the fauna and flora, typical of the riparian habitat, have become adapted to landscapes modelled by its needs, and it is certain that more than one emerged thanks to it.

With the almost total extinction of the beaver in Europe at the beginning of the 20th Century, the species that share its habitat have also been threatened. Since its return, the situation has improved in many places: amphibians, reptiles, water birds, dragonflies and other insects, as well as different plants and fungi, benefit from the constructions of the builder rodent.

The same thing goes for fish: true, sediments in suspension retained by dams can clog up the redds of trout, but the water that flows on downstream over the gravelly bottom of the river is only the clearer because of this. For migratory fish, beaver dams do not constitute completely uncrossable or permanent obstacles: they can be submerged by flooding or yield at different places. Studies carried out in Europe and North America show that the diversity of species of fish present in a water course is increased when the water is colonised by beavers.

A Partner in projects of riparian regeneration 

All that makes the beaver an ideal partner in projects for the the regeneration of rivers, and what is more, a factor in reducing the cost of such projects. It is, therefore, no longer necessary to remodel water courses using diggers at great expense; only a few civil engineering operations need to be carried out at the outset of a project. The beaver will then take on the responsibility of relaunching the freshwater habitat for nothing and in a completely natural way - as long as one leaves it enough space.

In some places, the beaver's activity can equally share in protection against floods, since dams placed in the upper reaches of small water courses can attenuate peak flows of flood water (Nyssen et al. 2011). But it is still necessary that riparian areas should be wide enough.

> More space, less conflict 

In a landscape exploited intensively by humankind, an animal that digs burrows in the slopes of banks and holds back the water of streams is not always welcome: its works interfere with those of humankind, which modify and regulate water courses to his own advantage and often exploits banks to the crest of their slopes. Technical solutions exist to resolve many of these conflicts, the most enduring being the widening of the riparian zone.

 Three quarters of the water courses of the Swiss Plateau are bordered by tracks that are accessible to motor vehicles, whether from one side or both. By digging burrows in the slopes of banks, beavers create a risk of collapse.

The building of dams constitutes another reason for conflict between man and beaver, because the retention of the water can bring about the raising of the water table, with possible saturation of the soil as a consequence.

The beaver is a protected species throughout Switzerland. This protection includes the habitat of the rodent, to the extent that it is forbidden to destroy its lodges or dams without  exceptionally granted licences from the competent authority.

If certain isolated individuals cause substantial damage or threaten zones of human habitation and infrastructure of public interest, they can be captured and killed, in conformity with regulations for the management of hunting. Such regulatory measures are authorised only for a limited period, which must be used to good effect to prevent further damage. Because the calm that follows the killing of an animal is generally of short duration: another beaver will usually come to dig in the same place.

Constructive measures of protection

There exists a whole suite of technical measures suitable for protecting infrastructures that have been installed near water courses:

> Wire mesh and stone stopping nets  (gabions?) placed on the surface of the bank make a barrier that is uncrossable for beavers, as well as musk rats and coypu which are spreading in Switzerland (size of mesh 10X10 cm for the beaver, and 5X5 cm for the musk rat and coypu). The installation of artificial burrows in netted slopes (Beck and Hohler 2000) allows beavers to feel at home (fig.5 right bank). Naturally, the installation of such devices should not compromise either the stability of the slope, or nearby tracks and roads.

> it is essential not to make breaks in the embankment of a water course whose bed lies above the level of the land neighbouring it, or when it is a matter of an embankment  against floods, or forming part of a hydro-electric operation. It is better to protect the embankment with the help of steel mesh nets or gabions. If it is possible to proceed to the exterior reinforcement and the levelling of the embankment, the mesh can be installed directly in the heart of the embankment. Beavers can thus dig as far as the artificial barrier without causing damage.

The embankment on the right bank must be laid out in such a way as to make up for the loss of stability due to the digging of the beavers (fig.5 left bank).

Technical measures for the prevention of damage by beavers are onerous and contribute little or nothing to the ecological restoration of water ways. They do not allow for the creation of new habitats or enrich the landscape. In this sense they are not appropriate except in places where the replacement of the infrastructure involved is impossible or too expensive.

On the other hand, the enlargement of space reserved for waterways constitutes a real plus for nature and the landscape. It extends the possibility of surfaces and structures near to their natural state, favours the development of varied habitats and resolves most of the conflicts between humankind and the beaver by limiting the space over which the beaver is likely to interfere with human activities. The risk of the collapse of tracks is reduced from a distance of about 5 metres from the top of the bank, because it is rare for beavers to dig beyond this limit.

Standing water created by beavers can be a problem for crops near banks, but only over small areas. The floodable area is limited to a riparian strip between 10 and 20 metres wide, except in extremely flat areas where the soil is gravelly and permeable.Unless this strip is being intensively farmed, coexistence with the beaver should not prove to be a problem, except in the case of backing up of water in drains (read fig.7).

As a consequence, restoration projects must give priority to areas of conflict.

Optimal management of banks

In the same way that the widening of space reserved for the riparian edge, which is the best arrangement for river banks, is a preparation for eventual conflicts. Levelled banks being ill adapted to the digging of burrows, the slope of the embankment should be between 1:5 and 1:3 (maximum) on the stretches where digging by beavers is not wanted. The transverse section of the water course is bigger in this case, which improves the flow capacity as well as the retention of water in case of flood.

One may foresee steeper banks (with a slope more than 1:3), ideal for the construction of burrows, on stretches where no infrastructure is installed in the immediate proximity of the water or on the ridge of the slope. (Fig. 6).

Drains and beaver dams

When a beaver builds a dam in a very flat agricultural area, it can cause retention of water in nearby drains. Trapped sediments can then block the drains, leading to flooding upstream in meadows and fields. An appropriate drainage system can help to resolve this problem. The other option is to transfer the affected areas into wet meadows which become home to a great diversity of species.

According to a census carried out by the federal Office of agriculture in 2008 (OFAG 2010), there are 192,000 hectares of artificially drained farmland today in Switzerland, perhaps 18% of the usable agricultural area. Two thirds of the drainage schemes date from before 1960. And a third of the network is in a bad state or in an unrecorded condition. There exists, therefore, an important need for renovation. In a general way, the outfall of a drain joins the stream just above its bed. If the beaver colonises or is likely to colonise such a water course, the renovation of drains should at least envisage the adoption of another solution - especially in the context of a project of renovation.

No need to reinvent the wheel. At Konolfingen for example (BE), a system that is compatible with the presence of beavers has been working for 100 years: in the Hünigenmoos, whose drainage for agriculture began at the beginning of the 20th century, drain pipes do not pour directly into the stream de la Chise, but into two collecting drains, dug parallel to the banks. The collectors carry the drainage water as far as a place where the fall increases, at which point it can join the main stream.

Such measures are easier to instal as part of a large scale project of improvement, applied to an extensive area, and subsidised by the Confederation and the canton.

An opportunity to favour wet meadows 

The renovation of a drainage scheme carries with it considerable costs, estimated by OFAG to amount to 25,000 Swiss francs/ha. (OFAG 2010). Continued agricultural exploitation may also prove to be expensive, especially if it is necessary to pump water, which is actually the case for 11% of the drained areas.

Taking account of the cost incurred, the opportunity to renovate a drainage scheme depends particularly on the nature of the soils involved. According to a cautious estimate by OFAG, about 70% of soils drained are in areas of intensive arable cultivation (OFAG 2010), which the sectoral plan of the Confederation recommends should remain as such to a large extent. In this set up, the renewal of drainage schemes is therefore an appropriate measure. For other areas, on the other hand, it is recommended to proceed first to an evaluation of the soils. If it appears that the necessary investment will bring very little advantage in terms of agricultural exploitation, the alternative solution lies in transforming the land near the water course to wet meadowland, with the support of the farmers (fig.8). This approach can be particularly profitable in the context of a project of restoration because the temporarily flooded areas constitute habitats of extreme richness, especially for species of amphibians threatened with extinction. Wet meadows used in such an extensive way are considered to be eligible for grant aid.

> Water courses that are welcoming to beavers

Here are several examples of existing restoration projects, which show how suitable management and an enlargement of the riparian zone can allow the renewal of embarked streams, to the extent that beavers cause no conflict. The suggested choice is in no way exhaustive.

Hermance, Pont des Golettes (GE)

In the 1990s, the canton of Geneva launched a programme of restoration for its water courses, and set up a special fund for financing it. One of the numerous projects carried out since then concerned a stretch of the Hermance inclusive from the Pont Neuf to the Pont des Golettes, to the south-east of Anières. As this stream constitutes the frontier with France, its management required the cooperation of the two countries.

Before the execution of the project, the bed of the Hermance at the level of this stretch was narrow and embanked by rock. On the left bank, trees grew to the crest of the embankment, while the right bank was entirely bare of trees. The restoration took place in 2010. It consisted of grading the slope of the banks, in bringing a morphological diversity to the river bed and enlarging the space allowed to the waterway, allowing it to expand from between 10 and 30 metres up to 50 metres wide (fig.9).

Aquatic and marsh species such as the bulrushes, iris, water plantain, loosestrife, common loosestrife, and several sedges and rushes were planted. To shade the waters and prevent  excessive warming of the water in summer, copses were planted on the banks. Food was thus more abundant for the beavers, which chose a managed burrow under the Pont des Golettes as their home, and actively exploit the restored water course.

Urtene, Kernenried (BE)

If the waters of the Urtene upstream of Kernenried (BE) have been able to benefit from a project of restoration, it is partly thanks to the sewage works at Holzmühle, carried out in 2001. Because the restoration work had for effect especially the improvement of the quality of the water of this badly polluted stream and as a repercussion the its improvement for fishing. To exploit this potential it was necessary only to manage the over dull course of a stream that was entirely embanked.

This programme of management undertaken between 2003 and 2007 allowed the enlargement of the space allowed to the water from a width of 15 to 20 metres. In the programme of reallocation of fragmented parcels of land necessitated by the  building of a new stretch of Rail 2000, acquisition of land was made easier by the fact that farmers became aware of compensations in nature.

Today, the Urtene has regained a bed of great structural diversity (fig.10). The varied vegetation of the banks and slopes (big deep rooted plants, shrubs and trees) give shade to some of the stretch. The waters have regained their proper dynamic: sandbars and gravel beds are deposited on flat banks, while zones of deposition and erosion are formed on steeply sloping banks. 

A survey carried out in 2008 concluded that a net improvement of the ecological situation had taken place. The number of fish has increased considerably and a new species that values the current has appeared: the barbel. The revitalised stretch has been stocked with brown trout and beavers dug their first burrow soon after the works had been completed.

Upkeep is the responsibility of a water management group (Wasserbauverband Urtenebach) which has prepared a management plan and employed two farmers part time to carry out works.

Grabenbach, Münsingen (BE)

Some years ago, the Grabenbach used to become engulfed in a subterranean gallery at the east entrance to the village of Münsingen and did not flow out again, except in times of great floods, as in 1968 and 1977, when violent storms made the water overflow and caused damage valued at millions of Swiss francs. To avoid a recurrence of such phenomena, a holding pond with a capacity of 40,000 cubic metres was built in 2009 at Mülital upstream of Münsingen and a new bed was laid out above ground downstream from the village.

To restore the subterranean stretch to the open air the bed of humus had to be taken from a stretch of land 20 to 30 metres wide, so that today the banks of the Grabenbach are adorned with a ruderal vegetation rich in species. The new watercourse flows into the Aaregiesse.

The project is accompanied by a long term monitoring of results, the first reports from which are promising: the aquatic vegetation is luxuriant (fig.11), the invertebrate fauna is distinguished by a great variety of species as well as a significant biomass: the brown trout is breeding successfully. Several beavers, settled lower down on the Giesse, have already been observed in the Grabenbach.

The management of the waters is the responsibility of the commune of Münsingen, which entrusts the works to specialist employees of the commune workshops.

Rheintaler Binnenkanal, Rüthi (SG)

Built more than one hundred years ago, the Rheintaler Binnenkanal drains the marshes of the Rhenish valley of St.Gall. In May 1999, when an exceptional flood caused the industries of Rüthi damages estimated at several millions of Swiss francs, it appeared obvious that this canal was no longer able to cope with such accumulations of water without flooding.

Studies then showed that the lowering of the water level could improve the protection against floods that it would be necessary in order to achieve that considerably to widen the bed of the canal as well as the riparian zone. 

The project, carried out from 2006 to 2007 on the stretch of the interior canal stated downstream from Rüthi consisted of widening the bottom of the bed, which only measured 8 metres, from 16 to 20 metres with excavators. The riparian zone, which was only twenty metres wide was expanded to a maximum of 65 metres (fig. 12).
Initially rectilinear, the canal now includes meanders, branches in several places and forms little islands of gravel, zones of calm water and ponds separate from the main stream in time of drought.

The revitalisation has had an extremely positive impact on the natural restocking of fish, to the extent that young nases (Chondrostoma nasus) have been noticed on this stretch after several years of absence - just at a time when the species is threatened with extinction in Switzerland.

The nearest population of beavers is living about three kilometres away, on the interior canal of Werdenberg (2013). For the present, beavers have not colonised the restored stretch, but they would find the necessary habitat there to build lodges.

the management of these waters is assured by the Rheinunternehmen establishment, on a mandate from the Rheintaler Binnenkanal association. This association was set up by the 12 communes situated along the interior canal with the objective of taking on the management of the waterways. Rheinunternehmen, a public body, with a team of specialist of its own, is affiliated to the Department of bridges and highways of the canton of Saint-Gall.

> Managing the waters while favouring the beaver

The ecological quality of a restored stream does not depend only on the levelling and the carrying into effect of the work of restoration. The continuing management of the waters and the vegetation of the banks is also all important.

In general, it is wise to found an association for the management of the waters for the stretch concerned, or to entrust the management to an existing management cooperative. The farmers of the agricultural land bordering the water course can thus carry out the necessary management on the basis of a previously arranged plan. Advice and offers of continuous training should ensure that the carrying out of those works of care and upkeep of the revitalised waterways is properly done.

The best being the enemy of the good, it is sometimes preferable to do nothing, especially in the sectors where the stability of the bed and the flow capacity are already assured. In that way nesting sites for birds can be spared, as can the habitats of many insects, which need time to develop. In the same way, it is not necessary to cut the meadows every year.

>To prepare reserves of food for the winter, beavers need to find enough tender wood near the river banks. If trees have been cut too low, beavers, deprived of their basic food, will have to migrate to a neighbouring stretch and dig new burrows there, which can in its turn lead to conflicts.

>It is, therefore, advised that so far as possible beavers should be entrusted with the cutting of wooded banks and not to use the chainsaw except as a backup.

>When burrows cause collapses on the banks it is not always necessary to fill the cavities. Sometimes a biological framework will be enough to fix the problem: this solution consists in planting all around the zone, on quite a large area, bushes with deep rooting systems, such as willows or alders. The subsidences are thus easily reparable by the farmers and the banks are stabilised. A staged riparian vegetation can then develop for the long term.
> The smaller the areas of intervention, the better.  Mowing the grass in short stretches allows little animals the possibility of finding shelter near the area of intervention (fig. 13).
>In the area of retention of beaver dams, it is noticeable that there is an enrichment of nutrients, which favours the growth of vegetation in the waters concerned and speeds up the deposition of sediments. On very flat stretches carrying much sediment, the process can be slowed down by the installation of sand traps.