Is a grading plan the same as a drainage plan?

They overlap, but drainage design may include hydrology, conveyance, storage, discharge and calculations beyond proposed ground contours.

Can I direct water to the street?

Only where local rules and the street drainage system allow it. Confirm legal and engineering requirements.

Why is the garage vulnerable?

Its slab is often low and connected to a sloping driveway, so poor transitions or drainage can direct runoff inside.

Do online contours show drainage accurately?

They can show broad terrain but may omit small constructed features and lack survey accuracy. Verify critical drainage in the field and with appropriate survey.

Residential Drainage Site Plan Basics for Early Feasibility

Understand residential drainage site plan basics, including existing flow, finished grades, roof runoff, swales, driveway crossings, discharge, and neighbor impacts.

Read the existing drainage pattern

Use contours, spot elevations and field observations to identify ridges, swales, low points, concentrated flows and off-site contributions. Check drainage easements, channels, culverts and known flooding. Public elevation data can screen broad patterns but may miss curbs, walls and small features that control residential drainage.

Relate floor level and finished grade

Set preliminary floor and pad elevations with positive drainage away from the building and workable transitions to existing ground. Consider entries, garage slabs, patios, window wells and neighboring grades. A high floor can reduce local flood exposure while increasing fill, slopes and impacts elsewhere.

Route roof and surface water

Estimate roof drainage directions and identify where downspouts or collection systems discharge. Preserve or create continuous surface routes that do not cross critical entries or trap water. Coordinate landscape, walls and fences so they do not block the intended path.