Hydrology/Stormwater: LARE 2

Low Impact Development Stormwater “Flow Path”

1. Green Roof

2. Permeable Pavement

3. Bioretention Basin with Underdrain

4. Water Harvest/Re-Use Cistern

Impervious Surfaces

Increase the volume and rate of runoff

Base Flow

Sustained flow of a stream in the absence of direct runoff

First Flush

Initial surface runoff from impervious surfaces with high proportions of concentrated pollution compared to the remainder of the storm

Non-Point Source Pollution

Pollution caused by rainfall or snowmelt moving over and through the ground, collecting pollutants and depositing them into lakes, rivers, wetlands, groundwater, and oceans

Total Maximum Daily Load

Calculation of the maximum amount of pollutant allowed to enter a waterbody to continue to meet water quality standards

Time of Concentration

Amount of time needed for water to flow from the most remote point in a watershed to the watershed outlet (not the furtherest point)

Surface Runoff

Precipitation that runs off the land’s surface and flows downhill

Recharge

Water that infiltrates the lands’ surface and percolates downward to the underlying water table

Water Table

Upper surface of groundwater

Groundwater

Subsurface water flow that discharges to streams, lakes, wetlands, or the ocean

Riparian Zone (“Area”)

Interface between land and a river or stream

Riparian Corridor

Area that encompasses a river or stream and the land adjacent to it

Floodplain

Composed of 3 areas: channel, floodway, and flood fringe

Channel

Portion of floodplain where stream/river flows under normal conditions

Floodway

Portion of floodplain that is used to convey floodwaters during a 100-year flood

Flood Fringe

Portion of the floodplain outside of the floodway that does not convery floodwaters and usually contains slow moving or standing water

Freeboard

Any portion of the floodplain outside in excess of the base flood elevation