In 2017 we collaborated with Colin Meurk, President of the Travis Wetland Trust to come up with cost effective wildlife bridge options. The wildlife bridge was needed to enable people and wildlife to safely cross state highway as part of plans for an expansion to the existing Travis Wetland in Christchurch, NZ. The wildlife crossing is to connect the existing Travis Wetland to a proposed “eco-zone” to be contained in the re-developed red zone and linking to the Avon River to the South. The crossing is required to cross Travis Road (SH74).
Our in-house architectural engineers combined a curved geometry with layers of native vegetation to create a “green bridge” aesthetic which successfully harnesses the concept of the crossing acting as a seamless continuation of the sanctuary across the busy urban road.
The Waitakiri Ecosanctuary is proposed as a 180-hectare area including Travis Wetland and 30 hectares of Christchurch’s residential red-zoned land. The proposed sanctuary would house some of New Zealand’s most endangered native species, including kiwi, white heron, saddleback, kaka and takahe. The goal of the proposal is to reconnect Cantabrians to an accessible experience of the charismatic, endangered wildlife, and natural habitats of New Zealand and the region. This is one of many ideas for re-using Red-zone land along with cycleways, recreation, and some residential development. If you want more info about the overall eco-zone proposal we recommend you contact Colin who has put much thought and passion into this project and what it’ll mean for Christchurch. More info about the Waitakiri Ecosantuary can be found here.
We worked with Colin to develop an options report/study to help his team consider the geometric and functional issues that were needed to form the basis for discussion on possible scale and crossing types. The study also helped the Wetland Trust understand the likely economics of the proposed bridge that could be factored into the overall economics of the proposals. Using a study of this type is a great cost-effective way to get a project off of the ground as it identifies feasibility and budgets early.
DCSS Travis Wetland Wildlife Bridge NZ – View on Bridge
Wildlife Bridge Design in NZ:
There is no set design basis for wildlife bridge / crossings in NZ but there are numerous international standards (particularly in the US and Netherlands). These codes recommend bridge types and usable widths for various types/sizes of animals and different configurations with and without people. Many of these standards focus on enabling crossing of large mammals (in the US the recommended width is 40m to allow large mammals). Clearly a 40m wide land-bridge was not within the likely budget for the Travis Wetland so we worked with Colin to agree sensible modifications to international standards that could be used to develop an economic crossing width. We looked at options that would allow NZ native birds and reptiles to share successfully with wetland visitors (people) crossing the road. Since the crossing is not intended for large mammals our review of the international standards concluded that a usable width of 5m (with planting etc.) would be acceptable for a shared wildlife crossing. We also considered modification to local culverts under Travis Road that proved a very economical option which could be used as short-term or medium term solutions while larger budgets are sought.
Wildlife Bridge Proposed Solution:
The proposed solution features a curved concrete culvert design with grasses and vegetated areas. The culvert would be created from two precast inverted T beams. Pedestrians would walk between the concrete up-stands and wildlife would pass either side. Wildlife would be protected from falling by either using small tunnels over mid-span or by applying wire fencing to the edge of the bridge. The curved culvert was considered a very cost effective option for crossing the road as it minimised the total span and relies upon simple construction methods to keep cost down.
