Kiloturds or decajohnnies would be good measures.
You can calculate flow over a weir if you know the height of water and the discharge coefficient, which you can look up, but I guess they CBA.
They don't do them any more, but Surfers Against Sewage used to have great T-shirts of a surfer riding a wave and wearing a gas mask. The current range is a bit meh. And it is probably some sort of crime for a non-surfer to wear a SAS T-shirt.