Stormwater Management Flashcards

What does the term 'impervious cover' refer to in stormwater management?

Answer: Surfaces that prevent or severely limit infiltration of water into soil

Impervious cover includes surfaces like pavement, rooftops, and compacted areas that prevent rainfall infiltration, increasing runoff volume and peak flows.

A stormwater retention pond differs from a detention pond in that a retention pond:

Answer: Maintains a permanent pool of water between storm events

Retention ponds maintain a permanent water pool that provides treatment through settling and biological uptake, while detention ponds drain completely between storms.

Under post-construction stormwater regulations, what is the typical maximum drawdown time for extended detention facilities treating the water quality volume?

Answer: 48 hours

Extended detention facilities are typically designed to release the water quality volume over 24-48 hours to promote settling of fine particles.

Which best management practice (BMP) is specifically designed to remove sediment from stormwater through gravity settling in a confined area before discharge?

Answer: Sediment forebay

A sediment forebay is a pretreatment cell at the inlet of a stormwater BMP designed to capture coarse sediment through gravity settling.

The term 'water quality volume' (WQv) typically represents runoff from which storm size?

Answer: A small, frequently occurring storm (e.g., 1-inch or 90th percentile)

Water quality volume is sized to capture the runoff from small, frequent storms (often 1-inch or the 90th percentile event) that carry the majority of annual pollutant loads.

Which component of a wet detention pond is critical for preventing short-circuiting of stormwater flows?

Answer: Inlet-to-outlet separation distance and length-to-width ratio

Adequate separation between the inlet and outlet (typically a length-to-width ratio of at least 3:1) prevents stormwater from flowing directly through without adequate treatment time.

What is the primary mechanism by which a permeable pavement system manages stormwater?

Answer: Allowing runoff to infiltrate through the pavement into a stone reservoir base

Permeable pavement allows water to pass through the surface and into an aggregate base reservoir, where it infiltrates into the subsoil or is released through an underdrain.