Landscape design in South Portland, Maine.

The city runs a combined sewer and storm system in parts of town and works under a municipal stormwater permit whose later phases called for erosion control and low impact development ordinances. For a residential design, low impact thinking is simply good practice here: roof water sent to a planted swale or a stone infiltration trench rather than the street, patios pitched toward lawn, and as little new pavement as the plan allows.

Soils vary within a few blocks. The plan lists Windsor loamy sand, which drains excessively, next to Lamoine silt loam, somewhat poorly drained, and Scarboro sandy loam, very poorly drained. A single design can cross all three, so the grading plan is drawn from what the ground does, not from what the lot looks like. On a sloping lot near Hinckley Park or Trout Brook, that can mean a dry swale at the low edge of the lawn instead of a pipe to the street, sized for the heavier storms the city has been recording.