1. Home
  2. TRID
  3. View Record
https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

Dry paths under water bridges as animal passages

Kuivapolut elainten kulkureittina. Vesistosiltojen rakenteen vaikutus elainten liikennekuolleisuuteen

Roads and traffic have many severe impacts on animals. One widely used way of mitigating harmful impacts are wildlife passageways one of which is dry paths under water bridges. Very little is known of dry paths, and in Finland they have not studied at all. In this project we tried to find out whether the road bridge structure affects traffic mortality of animals. We also produced the guideline for planning and construction of dry paths under water bridges in Finland. The study was carried out in southern Finland. We selected ten bridges with dry paths on both sides of a stream, and ten bridges without passage possibilities. For every bridge we explored control areas with similar landscape and traffic features but without streams. Then we measured a 400 meter long road section on every area. On the verge of the road on these areas we identified road-killed terrestrial vertebrates (mammals without bats, amphibians and reptiles) on ten occasions in the summer of 2008. Based on tracks we found under bridges we also consider species which used dry paths during the monitoring period. We found a total of 307 dead terrestrial vertebrates. Of these, 14.3 per cent of carcasses were situated on road sections in the vicinity of bridges with dry paths and 37.1 per cent on their control sections. Of all road-killed animals, 31.3 per cent were situated in the vicinity of bridges without passageways and 17.3 percent on their control sections. Dry paths were used by 16 species or species groups. We found that for example otters and raccoon dogs used dry paths regularly. Most of the tracks belonged to small mammals like voles and shrews. The largest species (except humans) we found to use dry paths was roe deer. Dry paths are most easily constructed on a new bridge or a on an old bridge during a wide repairment procedure when most of the constructure is being re-built. In some cases it is also possible to build dry paths on an old bridge when it is under minor renovation. The need for dry paths should be assessed before the planning of the building or repairing process takes place. It is important to notice that the water gap size need to be large enough also when dry paths are built. In some cases there is need to get a permit according to the water legislation. In this study we found that dry paths under water bridges are effective solutions to the need of reduction of traffic mortality in small and medium-sized terrestrial vertebrates. River and stream sides are known as ecological corridors and it is also known that road kills of animals are aggregating near water sources. It means that river and road crossing sites are potential targets when planning mitigation measures like passageway structures. This report may be found at http://alk.tiehallinto.fi/julkaisut/pdf2/3201146-v-elainten_kuivapolut.pdf

Language

  • Finnish

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 01321560
  • Record Type: Publication
  • Source Agency: TRL
  • ISBN: 978-952-221-275-7
  • Files: ITRD
  • Created Date: Nov 29 2010 11:39AM