Restoration of Raised Bogs in Denmark Using New Methods – a LIFE Project National Seminar 9/10 September 2010
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Restoration of raised bogs in Denmark using new methods – a LIFE Project National seminar 9/10 September 2010. Storelung. Restoration of raised bogs in Denmark using new methods Experience gained from the restoration of raised bogs and recommendations for further projects. This report is based on the results of the project and on the discussions at the national seminar on 9/10 September 2010. Havemosen at Store Økssø. LIFE Project Restoration of raised bogs in Denmark using new methods LIFE05 NAT/DK/000150 Text Jes Otto Buus, Helle Kold Jespersen, Søren Kjær, Leif Kogsgård Lyngsø, Martin Nissen Nørgård, Claus Simonsen, Annita Svendsen, Christian Brix Søndergaard, Else Benete Lei and Jesper Stenild Editors Jesper Stenild, Karen Glerup, Søren Kjær Photography The Danish Nature Agency, RisagerConsult, Jydsk Luftfoto Aerial photo, front page Kongens Mose viewed from the southwest. Photograph: Jydsk Luftfoto Graphic design Glindvad Grafisk Design MILJØM K Æ S R I K D N R I N O 1,000 copies printed on paper bearing the Nordic Swan ecolabel. G N ISBN 978-87-7279-259-0 541 006 Funding Produced by the Danish Nature Agency with support from the European Union’s financial instrument, LIFE. This report forms part of the reporting of the LIFE Nature project, RERABOG. The purpose of the project is to restore raised bogs in Denmark, which includes trialling various methods and techniques under Danish conditions. The project period ran from 2005 to 2011. The project was run by the Danish Nature Agency. Brandstrup Mose. Contents Introduction . 5 Preparatory studies. 6 Applications to authorities . 8 Contact with nearby residents and landowners. .10 Information for the local community and public facilities. 11 Clearance of scrub and trees. .13 Experience of tendering process . .14 Blockage of ditches and drains. .15 Combating overgrowing . 22 Monitoring. 38 Examples from individual project sites. .40 LIFE Project · Restoration of raised bogs in Denmark using new methods 3 4 LIFE Project · Restoration of raised bogs in Denmark using new methods Kongens Mose: Blocked ditch with heavy regeneration of peat. Introduction This booklet collates the experiences gained throughout the en- What solutions are to be used in an individual project depends tire project period. These include our own experiences, but also on many different parameters, but with the aid of this compen- those of similar projects both in Denmark and elsewhere. dium of examples we hope it will become easier to put together One thing is certain, and that is that each project area is unique solutions based on the factors that apply to the project that is and there are no cut-and-dried solutions. The remnants of raised about to begin. bogs in Denmark are all affected by the interventions of the community surrounding them to such an extent that there are no “ready-made” formulas for their restoration. Prevalence of raised bogs in 1919, as part of the bog communities larger than 5 hectares. (Made from Prevalence of raised Thogersen 1942). bogs in 2000. LIFE Project · Restoration of raised bogs in Denmark using new methods 5 Preparatory studies In restoring raised bogs, hydrology that is as close to the optimal In the most complicated projects, it may be necessary to actually as possible will be crucial. produce a hydrological model based on setting up sounding It will therefore always be a case of changing the drainage con- pipes and measuring the water level over a relatively prolonged ditions, and that can have consequences for biology, for the ex- period. Producing a model of this kind is quite costly and usually ploitation of neighbouring areas, for technical facilities and so requires external advice. The project included both sites like on. Preparatory studies will usually be necessary, to one extent Kongens Mose that need extensive surveys and sites like Store or another, in each of the following fields before a restoration Økssø and Boestmose, where there were adequate knowledge project: of the ditch and drainage systems. • Hydrological studies Example: • Ownership studies • Biological studies Kongens Mose • Technical studies Kongens Mose is a very large bog with complicated drainage conditions, which has been extensively exploited and drained. Preparatory hydrological studies For the state-owned areas of the bog, no drainage plans exist. There is always a need to evaluate how a rise in the water level There are significant economic interests in agricultural land in affects the project area in question and its surroundings. the border areas along the bog, which mean that any inaccuracy As a minimum, there should be a survey of the terrain and exi- in working out the area of impact will have major economic sting drainage of the project area and its surroundings. Contour consequences. lines can be obtained using grid levelling, aerial laser scanning It was therefore decided to produce an integrated watercourse or by purchasing the Danish National Survey and Cadastre’s di- and groundwater model to illustrate the drainage conditions and gital elevation model of Denmark. An overview of the drainage the effects of closing up various ditch systems. One prerequisite conditions can be obtained from drainage plans and plans of the for being able to set up such a model is that sounding wells have ditch systems, where these exist. Sources may include previous been put in place in order to record groundwater levels. drainage projects or DDH’s drains archive. Long-term neighbours The model is an excellent tool with which to target the ongoing and landowners can also be good sources of such information. work, so that drainage systems are closed where they impact the The information about the type of terrain and existing drainage conditions of the bog. The model has also been used to determine will still be too imprecise to enable evaluation of the impact on the consequences for privately-owned land areas in and beyond the project area and surroundings. the bog, for access roads and other facilities. The model is also The need for further studies of the hydrology can be assessed on an important tool in future management of the bog, as it gives the basis of the following parameters, among others: some insight into future moisture conditions. This allows one to assess whether, following the closure of ditches, the bog will • The complexity of the hydrological conditions still be dry enough for the birch to survive, which means that • The number of private owners clearence of tree growth will have no long-term effect. • The types of sites The report describing the model is very technical, and it is not, • Technical facilities in itself, suitable for public use, but it is a good starting point for • Natural assets communicating the impact of a project, and particularly for com- • Economic interests municating the knowledge and the painstaking work behind the decisions about activities to be undertaken. One option is to get an experienced adviser to assess this need. Producing such a model is a specialist job, and quite an expensive It is a good idea to clarify with the authority responsible for the one (the Kongens Mose model, for example, cost DKK 300,000). watercourse in question what requirements they have in respect Parameters to consider when purchasing the production of a of documentation of the impact on drainage of any action on model shall include the size of the project area, the complexity cases under the Watercourse Act. of drainage conditions, existing basic data (it costs time and money to collect data), the anticipated scale of impact beyond the project area, and the overall economy of the project. 6 LIFE Project · Restoration of raised bogs in Denmark using new methods Recommendations: assets will be affected by restoration, it is important to have them investigated and registered at an early point in time through a • The impact of changed hydrology should always be preparatory biological study. studied. The data obtained should be incorporated into any assessment • The level of the preparatory studies should be adapted of whether a project should be set in motion. The data should to the topography and ownership situation of the also be used if the project progresses any further, for example in project area. applications to the various authorities. At the same time, the data represent an important element of Preparatory studies relating to ownership the work that should always be taking place to inform the public. The ownership situation in the project area and the closest surroundings must always be known. Both municipalities and Preparatory technical studies the state now have easy access to ownership data via cadastral It is important to have an overview of what technical facilities maps, the Geographic Information System (GIS) and the land could be affected by the project, both those that are visible and register. those that may be below ground. For a fee, data about cables can be searched in the Danish Register of Underground Cable There are 3 important reasons to know the ownership situation: Owners (LER) database (www.ler.dk), or this can be done via a contractor where appropriate. If there are technical facilities 1. In order to be able to inform owners and neighbours or cables in a given land area, it is important to contact their about the project – perhaps right from the concept owners as changes in the hydrology and digging work, in par- stage. ticular, can represent problems that may have practical and 2. In order to be able to evaluate the need for hydrological economic consequences for the project. studies. 3. In order to be able to evaluate whether there is a need, Example: in connection with the project, for actually purchasing land, for land swaps or substitute land from a govern- Brandstrup Mose ment pool.