Floodplain rules and substantial improvement
Structural repair inside a mapped floodplain is where the city's floodplain guidance genuinely matters, because the cost of work relative to the structure's value can trigger additional requirements. Excavation for exterior drainage can also run into stream buffers. Both are established from the parcel. Neither changes what is wrong with the foundation, but both can change what the repair is permitted to involve.
Official sources
Establish flood status before scoping structural work
Citywide flood guidance cannot establish your parcel's zone, your buffer lines, or what is actually causing the movement. Get the first two from the city and the third from an engineer who is not selling the repair, before committing to any scheme.
Sources reviewed June 20, 2026. City code and flood maps change on their own schedule, separate from this page.