Timber bridges often provide fauna habitat
16 December 2015
Many regional roads have timber bridge structures across local rivers and creeks. These structures have been there for a very long time (often built in the early 1900's) and are starting to show their age. They are rapidly being replaced across Queensland and New South Wales with single span concrete bridges and culverts.
Local governments undertake due diligence investigations into environmental, cultural heritage and native title issues prior to their removal. These investigations incorporate desktop and field inspections to assess the risks and liabilities before gaining permits and approvals under state and commonwealth legislation.
Redleaf Environmental have conducted over 50 bridge and culvert crossing assessments in the past 12 months for a number of local governments. In our assessments, we provide a high level of confidence for council regarding their legal responsibilities toward environmental issues and cultural heritage values for a site.
These assessments are necessary to confirm the likely environmental constraints and approvals required prior to issuing of construction tender documents. The investigations can include:
- database searches for listed threatened species (EPBC Act 1999 and Nature Conservation Act 1992);
- state mapped regional ecosystems (VM Act 1999) and threatened ecological communities (EPBC Act);
- environmental clearances of stream crossings (waterway barrier works – compliance with the Fisheries Act 1994);
- water quality issues; and
- cultural heritage duty of care assessment under the Aboriginal Cultural Heritage Act 2003.
Some of the fauna species that can be affected by removal of timber bridges are microbats which roost in the timber crevices and the aquatic fauna such as Murray Cod, Mary River Cod, Lungfish and threatened turtle species. Timber bridge abutments and pilons provide excellent aquatic habitat and often retain permanent waterholes while much of the stream is dry.
Redleaf Environmental scientist provide innovative mitigation measures to offset the loss of these structures to the fauna whilst still allowing for the project to proceed. One such example is where artificial microbat roosts can be built and attached to the new concrete bridge. We successfully relocated a roost of about 80 microbats within days of the old timber bridge being demolished.
Custom built timber roosts attached to new concrete bridge
Large footed Myotis, stream specialist which can roost in timber bridges
Threatened White-throated snapping turtle habitat in and around timber bridges including nesting banks
Platypus burrows can often be near or under old timber bridges