Storm & Flood Damage Recovery in Portland, ME

That is coastal flooding rather than a drainage failure, and on a peninsula the two are easy to confuse. A storm surge on top of an already high tide raises the water at the shoreline above the level of the low streets, and the drainage system that normally discharges there is under water. Nothing needs to be blocked for it to happen. The astronomical tide and the surge forecast together predict it better than any rainfall figure.

In this climate that is usually frost rather than settlement. Water in the soil behind a granite or rubble wall freezes and expands each winter, and over many seasons the wall moves. Because the wall has no drainage layer behind it, the soil stays wet and the cycle repeats. Rebuilding or repointing without dealing with the water means the same movement starts again, so drainage has to come first in any lasting repair.

Work with it rather than against it. Where rock is close beneath a cellar, there is very little soil to absorb water and the backfill around the wall fills up instead. A footing drain that actually discharges somewhere lower is the thing that changes the outcome, and on a peninsula with limited fall that discharge point can be the hard part. An interior perimeter drain to a sump is the usual fallback where gravity is not available.