Hello out there??!! We have been quiet on the blog but also busy advancing on our research, creations, and engagement programs with schools and preparing for an exciting arts festival in Bangor (Metamorffosis). Today though we are excited to share a newly published paper based on our ongoing efforts to map road-river infrastructure across Great Britain (GB: England, Wales, and Scotland).
In this study, we worked to identify where roads and rivers meet, and to validate or model whether infrastructure at these locations were bridges or culverts. Validating more than 110,000 road-river crossings, which we initially mapped in GB, was not really feasible as a starting point, so we focused on validating the type of infrastructure at 10% of those locations as a start. We used Google Earth tools and Digimap to validate the type of infrastructure at a road-river crossing.
The validation was led by James (who is now at River Restoration Centre); he located over 10,000 road-river crossings and determined if these were bridges or culverts for inclusion in a training dataset that we then used to create our models. Based on the validation and modelling we determined that there are likely to be more bridges than culverts along rivers in GB: roughly 60,000 bridges and 50,000 culverts. Bridges are often easier to identify in the waterscape (larger size, fewer trees around them, etc), whereas the smaller and rather cryptic culverts can be more challenging to locate. The crypsis of culverts contributes to the negative impacts they can have on water, species, and material movement in rivers.
We also determined several rules-of-thumb regarding where, based on our modelling, we can more confidently say that road-culverts are likely to occur along rivers in GB. First, if there is more than 10km2 of a catchment area draining to a crossing we predict that 75% of the time a culvert will be present. Second, we can more accurately identify culverts on major and local roads than other road types. These rules of thumb are likely to be useful for people who are trying to locate as well as better understand and quantify the impacts of these and other structures on our rivers.
The validated and modelled data for bridges and culverts are available on Figshare and we welcome collaboration on related questions and hope these data are useful for others.