What is a Stormwater?

Understanding Stormwater

Stormwater is water from rain or melting snow that moves across land or built surfaces. Natural ground can absorb much of this water. Roofs, concrete, asphalt, and compacted soil reduce infiltration. The water then travels downhill toward a drainage system, stream, pond, or low area.

Related glossary terms: Runoff, Catch Basin, Best Management Practice.

As runoff moves, it can pick up sedimentleaves, fertilizer, oil, metals, and other pollutants. A roof usually contributes cleaner runoff than a parking area. Roof debris can still enter gutters and downspouts. Good drainage separates water from building components. It slows or filters flow before reaching a waterway.

How Stormwater Works, Is Measured, or Is Used?

Rainfall first lands on a surface. It then either infiltrates the soil, evaporates, or becomes runoff. Runoff amounts depend on rainfall intensity, storm duration, surface area, slope, and soil type. They also depend on the percentage of hard surface. A common engineering method estimates peak flow with the rational method. It uses Q = C × i × A. Q is peak flow, C is the runoff coefficient, i is rainfall intensity, and A is drainage area.

Homes commonly manage roof runoff through gutters, downspouts, extensions, splash blocks, and underground drainage. A gutter collects water at the roof edge. It sends water to a controlled discharge point. A catch basin, rain garden, dry well, or other best management practice may handle runoff. These systems help manage larger or more complex areas.

Drainage professionals review the roof area, gutter slope, downspout spacing, outlet location, and receiving ground. They also inspect whether soil can absorb water. They check whether flow will remain at the surface. Local rainfall data and applicable building or drainage rules help determine system capacity. This review shows whether the system can handle expected storms.

Why Stormwater Matters?

Uncontrolled runoff can erode soil, stain siding, saturate planting beds, and collect beside a foundation. Repeated wetting may contribute to basement moisture, crawl-space humidity, settlement, or scene damage. Water that leaves a property too quickly can increase nearby channel flow. It can also increase pollution in nearby drainage channels.

Stormwater planning helps property owners protect structures. It also helps reduce harm to nearby waterways. A properly directed roof discharge keeps water away from vulnerable walls and foundation edges. Leaf guards can reduce gutter blockage. They don't replace adequate slope, outlet capacity, or routine inspection.

When Stormwater Matters Most?

Stormwater deserves close attention after heavy rain, roof replacement, landscaping changes, driveway work, or nearby construction. These changes can alter the amount, speed, or direction of runoff. Watch for overflowing gutters, standing water, soil channels, washed mulch, stained foundation walls, and water flowing toward a neighbor's property.

Memphis properties can face intense rainfall, clay-rich soil, mature trees, and flat or gently sloped lots. These conditions make discharge location and soil absorption important design questions. During an evaluation, check downspout distance from the foundation. Check whether outlets remain open. Check whether water reaches a stable area without causing erosion.