During dam construction I've had some clients install rolls of chain link fence...note these were small dams and it was economically feasible. At least the dam structure is protected this way, but rats can obviously still use other bank areas on the pond, but won't threaten the integrity of the dam. I've never read about rats causing a dam to fail, but better safe than sorry.

Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau

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