英语语法分析

The Yellowstone is America’s longest undammed river.

黄石河是美国最长的没有堤坝的河流。

Scenic river designations for the Delaware, White Clay, and other rivers will ensure that these rivers remain undammed forever.

这些自然野生风景区的称号将确保特拉华河、怀特克莱河等河流永远不会被筑坝的破坏。

However, in the four decades since thebuilding of the Glen Canyon dam, just upstream of the Grand Canyon, the onlysediment that it has collected has come from tiny, undammed tributaries.

然而，自从四十年前建起格兰峡谷大坝，仅大峡谷上游唯有能从微小的、无坝的支流中收集到沉积物。