I started one and accidentally deleted it the other day and then went meh... Anyway, it's obviously really. Look at all the possible alternatives before picking the best one. The jury is out on what is the best way to harness the estuary's potential. There's all sorts of alternatives: fences, lagoons, underwater turbines etc... Also is where the barrage is planned to go even the best place for it? There are several other possible locations for it... As well as all the pros, there's also plenty of cons which need to be adequately addressed - they're all well known. Ones that haven't been mentioned so far include: Siltation (probably not that bad - could in fact become a valuable resource in the future!); the likely death knell of the BPC's deep sea container terminal proposals that have now got planning consent and resultant compensation; energy subsidies that will make the wind turbine ones look like chicken feed (the public might not pay up front - but you can bet your bottom dollar that we'll be paying 'downstream'!); increased flooding and coastal erosion on the seaward side of the barrage; the epic CO2 costs of pouring a gazillion tons of concrete into the estuary; the fact that if you suddenly realise you have indeed built the world's biggest white elephant - it's going to be ****ing difficult to remove it again... And that's just off the top of my head... There's also tons of pros too, obviously. So my preferred plan is simple: Make sure you choose the right option, and make sure you build that option as well as you possibly can to extract the maximum benefits possible! It's not rocket science...