BOTRÄSKET WETLAND, MUSTASAARI, FINLAND

Transcription

1 Life+ Return of Rural Wetlands BOTRÄSKET WETLAND, MUSTASAARI, FINLAND Text: Juha Siekkinen, Life+ Return of Rural Wetlands, Finnish Wildlife Agency, Photos: Juha Siekkinen Maps and aerial photos: National Land Survey of Finland license number 326/MML/11 and 053/MML/13 1

2 BOTRÄSKET WETLAND THE OBJECTIVES AND LOCATION The objectives are to Create habitats for wetland fauna, in particular for waterfowl Promote biodiversity, landscape and multifunctional land use Act as demonstrative site of wetland work in the region The location

3 THE COSTS OF THE CREATION OF THE BOTRÄSKET WETLAND Total wetland area 6,0 hectares, of which open water area 3,0 ha and 3,0 ha artificial islands, medium water depth about 0,4 m Total costs of the creation (incl. VAT 23 %), Life+ Return of Rural Wetlands accounted 100%: Excavator and tractor works : excavation of channels, construction of the articifial islands, excavation of 100 m new ditch and landscaping. Materials 950 Wetland planning and field working Machineworks conducted by Sven Håkans from Södra Vallgrun, Mustasaari and his team in and Wetland implementation planning Juha Siekkinen Life+ Return of Rural wetlands in collaboration with Rolf Sund (representative of the landowners) and Södra Vallgrund Jaktförening r.f. ( Södra Vallgrund Hunting Society ), especially Mikael Ehn. Wetland management: Södra Vallgrund Jaktförening r.f. Waterfowl hunting is possible in Boträsket wetland and it is coordinated by the landowner and Södra Vallgrund Jaktförening r.f. Waterfowl censuses are the basic tool for determination of sustainable hunting levels. Waterfowl censusing in environmental monitoring waterfowl point counts 4 times/year: 2 counts in late spring, 1 brood count in July and 1 late summer count in the beginning of August (before the beginning of hunting season) conducted by Södra Vallgrund Jaktförening r.f.

4 BOTRÄSKET AREA BEFORE AND AFTER THE IMPLEMENTATION Aerial photo left, photographed in 2009: before wetland implementations the area was open mire area, where the tickness of turf layer varied cm. About 50 years ago Boträsket was partly shallow and open water lake. Then the new ditch was excavated on northeastern site which lead the current flow next to the lake, and gradually during the decades the area began to be hydrated and it turned to swamp-like, wet biotopes Aerial photo right, photographed in 2014: After implementation water areas and islands are visible New ditch to wetland Ditch, which led water to flow next to the wetland Artificial islands Water control structure Outflow

5 WETLAND PLANNING IN 2011 Juha Siekkinen Collaboration in planning started in the beginning of wetland project Above: Field planning with Game manager Stefan Pellas and Mikael Ehn (Södra Vallgrund Jaktförening r.f.) Left: Arto Rautio and Jukka Pietarila Metsähallitus Natural Heritage Services conducted the topography levelling in Boträsket area. Juha Siekkinen

6 EXCAVATION WORKS IN BOTRÄSKET IN 2012 Excavation works were done Excavation works had to be done during winter period, because area was very wet and turf layer was usually more than 1 m thick. The excavator machines (weight tons) were able to operate though ground was not frozen. Juha Siekkinen

7 Wetland was created by digging 2-6 m wide and 0,3-0,8 depth channels Excess soil which was digged, was spread around the wetland and partially to the artificial islands SUUNNITELMA J. Siekkinen/ Maanmittauslaitos ja Kemijoki Oy 1998 KOSTEIKKO VALMIS Maanmittauslaitos, kesä 2013 Juha Siekkinen

8 EXCAVATION WORKS IN NORTHERN AREA OF BOTRÄSKET IN 2012 In northern area, the aim was to create about 1 ha open water area near the clubhouse of Södra Vallgrund Jaktförening Turf was heaped up in 2012 In next wintern turf was spread around the wetland and transported to the vicinity of wetland by tractors. Juha Siekkinen Juha Siekkinen

9 Juha Siekkinen, The excess soil was digged to the depth of cm. Water depth of cm is most suitable for dubbling ducks like mallard, widgeon and teal. Digged material was spread afterwars around the wetland and to artificial islands Juha Siekkinen

10 INSTALLING THE WATER CONTROL STRUCTURE Water control structure, the overflow dam with wooden wall was constructed to the east side of the wetland by members of Södra Vallgrun Jatkföreningenin Logs are of Siberian larch for its durable and waterproof qualities. Logs in stand were mounted with steel bolts every one meter to the horizontal logs. Furthermore every logs in stand were nailed to the horizontal larch logs. Juha Siekkinen

11 The wooden wall was placed in to the new excavated outflow ditch. Next to the both ends of the wooden wall, 5 logs were pressed in stand to prevent leaks. The height of wall outlet was sawed to the desired lowest water level. With movable logs water level is possible to increase up to 50 cm Juha Siekkinen

12 These 7 logs prevent leaks, bceause they have been pressed to untouched ground Juha Siekkinen

13 The height of wall outlet was sawed to the desired lowest water level. With movable logs water level is possible to increase up to 50 cm and also the dewatering of wetland is possible. Finally the wooden wall was sealed with wood tar, which has been used traditionally to seal e.g. wooden boats and it is a pure natural product produced from pine wood. Juha Siekkinen

14 The downstream was excavated and covered with filtering cloth and rocks from cm Juha Siekkinen

15 BEFORE WETLAND CREATION Juha Siekkinen WETLAND FINISHED Juha Siekkinen

16 BEFORE WETLAND CREATION Juha Siekkinen WETLAND FINISHED Juha Siekkinen

17 Hunting is possible in Boträsket wetland. Infoboard near wetland gives information about wetland creation project and Life+ Return of Rural Wetlands project. Boträsket wetland area welcomes public for recreation and visiting! Juha Siekkinen