WHAT ARE STORMWATER AND DRAINAGE?

Follow the water to understand how a drainage plan is designed to work.

By Bea Byline | Life of a Sardine™

Stormwater is water produced by rain that moves across the ground and other surfaces. Drainage describes how that water is collected or moved through an area.

Development can change the way water moves across a property. Natural ground may absorb some rainfall, while roofs and pavement can create runoff that must be managed. A drainage plan helps show how the proposed system is designed to handle that water.

When reading one of these plans, begin with a simple question: Where does the water go?

Look at the direction water is intended to travel across the site. A plan may show ponds or other structures used to manage runoff. Follow those features through the drawings rather than looking at one structure by itself.

The property boundary is also important. Water does not stop moving because a line appears on a site plan. If the plans show water leaving the property, look for the location where that occurs. Then determine what the records say about where the water goes from there.

Elevation information can help explain the proposed movement of water. Changes in grading may affect the direction runoff travels. Pipes and other drainage structures may show how water is intended to move through portions of the system that cannot be understood simply by looking at the surface of the property.

A drainage plan is also a document created at a particular point in the development process. Check its date. Look for later revisions. If another record refers to a drainage calculation or permit, follow that reference before assuming the plan in front of you tells the entire story.

Most importantly, distinguish between what a plan shows and what happened on the ground. A plan can show how a drainage system was designed. By itself, it does not establish how the completed system performs during a storm.

So instead of stopping with “Does the project have a drainage plan?” ask a better question:

How is the proposed drainage system designed to move and manage the water?

Then follow the record from there.

Document. Fact. Unanswered question. Next record.

Nothing to see? Hold my pencil.

BEA BYLINE

Life of a Sardine™