What kind of man made feature would likely lead to sand loss on a beach regardless of active margin (west coast North America) versus passive margin (east and Gulf coast of North America) setting for the coastline?

Dam construction.

Explanation:

As a part of man-made features, the dam is an artificially created reservoir that is mounted on the river and it involves a huge amount of investment in terms of the time and the construction matter.  With the passage of time, this dam tends to have leakage of sand and soil matter due to the force of gravity and is always shaky in nature due to the tectonic activity of the region and is viewed as an active margin that can get broken or washed away. While the passive margins of the gulf cost pf North America is a transitional zone of land and water sphere.

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