1. The new dam was a bulwark against future floods.
    新水坝是将来抵御洪水的屏障。

2. They built up an earthen dam.
    他们建起了土坝。

3. The arch has a span of 60 metres.
    那个拱的跨度为60米.

4. Presently, all we can do is look at mug shots and stick our fingers in the dam.
    而目前，我们所能做的就是看看罪犯的照片，并参与到构筑抑制犯罪的大坝中去。