Or is it?

The most effective way for a river to be longitudinally connected is by weir removal, as this will lead to the most fish passage improvements, as well as reconnect sediment transport in the reach. Often this is not feasible due to many constraints – at a navigation for example. But sometimes a technical fish pass is preferred over weir removal. Due to uncertainties and risks, often over the behaviour of the river upstream.  A weir removal will lead to greater variety of in-channel habitat than a technical pass, which will retain the current water levels. And so would generate new habitat which could be included in the BNG metrics.

Will this encourage developers and structure owners to be braver at the options assessment stage to obtain the BNG points, rather than taking a more risk averse approach? It could be argued that an as-nature bypass channel, assuming it creates suitable habitat will also provide quantifiable (BNG) habitat improvements. 

A need to improve connectivity at structures

Will we now see a preference for more natural fish passage solutions? We will see, as BNG becomes further embedded in the planning process, there is a lot to get to grips with but our breadth of experience is developing rapidly!

For clarity, I’m not saying that fish passage improvement works are a silver bullet or the only form of improving our rivers, but often there is a clear need to improve connectivity at structures, and I am pulling on that thread. I think the above analysis could apply to the connectivity of terrestrial habitats, in that BNG metrics and their focus on habitat presence may be reducing the breadth of opportunities to improve our rivers in the next few years.