Following an Advisory Visit that Tim Jacklin and myself provided on the Lagan in Northern Ireland in July, the boys at the local club (lead by Hon Sec Michael Shanks) wasted no time in implementing one of our suggestions.
A very simple and extremely cheap modification to an existing weir will now ease upstream passage for resident and migratory fish. All it took was the addition of an angled baffle (in this case a low concrete kerb) to the sloping face of the weir. This will hold up enough water behind it for fish to swim up when the water flows down the weir face.

The baffle


Note the notch cut in the weir lip to focus water flow down the face of the easement (this notch may be made a little deeper if necessary)


The flow down this adjacent flume is incredibly fast and powerful (sometimes used to power a turbine) and is way too powerful for fish to swim against. However, when fish need to move upriver, a simple steel panel hatch will be lowered into the head of the slot and the water will overtop the weir lip and flow down the easement


When there is flow down the face of the weir, the lower tail will be drowned out and fish will be able to swim up alongside the baffle


Total cost - a bag of concrete and some expansion bolts.

Nice one guys.