# How Do You Calculate Impervious Area?

## What means impervious?

1a : not allowing entrance or passage : impenetrable a coat impervious to rain.

b : not capable of being damaged or harmed a carpet impervious to rough treatment.

2 : not capable of being affected or disturbed impervious to criticism..

## What does impervious surface area mean?

An impervious surface is a hard area that doesn’t allow water to seep into the ground. Instead, the water runs off the impervious surface, picking up many types of pollution in the process, and then flows into a storm drain or a nearby body of water.

## What is impervious square footage?

• What is an Impervious Surface? An impervious surface area includes and hard-surfaced, man- made area that does not readily absorb or retain water, including but not limited to building roofs, parking and driveway areas, sidewalks and paved recreational facilities.

## Do pavers count as impervious?

Permeable pavers are different from pervious and porous pavers in that rainwater passes around the paver opposed to through it. Permeable is a term used to describe paving methods for roads, parking lots, and walkways. … Water enters the joints between the solid impervious pavers and flows through the paver system.

## What is effective impervious area?

Effective impervious area (EIA), or the portion of total impervious area (TIA) that is hydraulically connected to the storm sewer. system, is an important parameter in determining actual urban runoff. EIA has implications in watershed hydrology, water. quality, environment, and ecosystem services.

## Are pavers considered concrete?

Regular pavers should be treated just like any solid surface such as concrete. The surface should slope away from the house and surface drains should be installed as needed to handle the water.

## How much do permeable pavers cost?

The cost of permeable pavers is approximately \$4.00 to \$6.00 per square foot, with the cost varying slightly with the availability of materials. As an example, the cost of an average-sized permeable driveway is approximately \$5,000 or more, including installation.

## Why are impervious surfaces a problem?

The problem with impervious surfaces is that they prevent the natural soaking of rainwater into the ground and slowly seeping into streams. Instead, the rain water accumulates and flows rapidly into storm drains. This results in severe harm to streams in three important ways.

## Which is an example of an impervious surface?

Impervious surfaces are surfaces that allow little or no stormwater infiltration into the ground. … Examples of impervious surfaces: Streets, roofs, parking lots, most patios, walkways, or anything else that does not allow water to flow through and into the ground (asphalt, concrete, plastics).

## How do you calculate impervious coverage?

TO COMPLETE THE MAXIMUM SQUARE FOOTAGE OF IMPERVIOUS COVERAGE ALLOWED ON A LOT, MULTIPLY THE PERCENTAGE ALLOWED IN YOUR ZONING DISTRICT BY THE TOTAL SQUARE FOOTAGE OF THE LOT (EXPAMPLE: A LOT MEASURING 7,500 SQ. FT. WITH A 40% ALLOWABLE COVERAGE WOULD HAVE AN ALLOWABLE MAXIMUM IMPERVIOUS COVERAGE OF 3,000 SQ. FT.)

## Do decks count as impervious area?

Land covered by materials such as concrete, stone, wood, or asphalt – which are commonly used in driveways, sidewalks, patios, and decks – count as an impervious surface area.

## Are permeable pavers good?

Permeable pavers solve problems and look good. … Permeable pavers, also known as permeable interlocking concrete pavement (PICP), provide stormwater management by reducing runoff volume and rate, filtering pollutants and keeping water on site without the necessity of retention ponds.

## Is concrete impervious?

Flooding. The number one contributor to urban flooding is impervious surface. Concrete and asphalt do not absorb water and instead create runoff from flash flooding from stormwater during rain events. Stormwater runoff floods streets then moves into homes and businesses creating extreme flood damage and safety hazards.