Such structures have been built across the River Thames in London, and a similar barrier project is underway in Venice, Italy. But, in addition to requiring substantial investment, this approach raises serious questions, reflecting uncertainty about the effects that river flows can have on harbors, the environmental consequences of closing a bay, and the impact on shipping.
同属此类地区的纽约市提出了一个替代方案：在港区入口处建设大规模风暴潮堤岸，在大风暴来临时可以关闭。伦敦泰晤士河已采取了这样的做法，意大利威尼斯也在建设类似的堤岸工程。但是，这一做法不但需要大量投资，还会造成严重问题，比如河水径流对港口的影响、关闭港湾的环境影响、对航运的影响等不确定性。