Low Impact Development

What is Low Impact Development?H i s t o r i c a l l y, Iowa rainwater stayed where it fell,soaking into healthy prairie soils to replenishg r o u n d w a t e r. To d a y, rainwater is often sent intostorm sewers where it is flushed into our streamsand rivers along with pollution from roads, parkinglots, or yards. As we add more roofs, pavement, andcompacted turf to our communities, it is moreimportant than ever to help rainwater infiltrate – tominimize flooding and protect water quality.

There is a changing trend in land development andstorm water management throughout the UnitedStates. It has been called many things, includingsmart growth, conservation development and lowimpact development (LID).

LID is an alternative, ecologically-sensitive designapproach that mimics the way natural areas storeand infiltrate rainwater. The LID approach protectslocal and regional water quality by decentralizingstorm water management and absorbing rainfallthroughout the landscape.

Low Impact Development2 0 0 5. . . absorbs ra i n w a t e r, p rotects water quality, minimizes flooding

In typical urban settings, soils areheavily compacted from the develop-ment process. Land is also coveredwith impervious surfaces, such asroofs, streets and sidewalks.C o n s e q u e n t l y, land is unable to absorbstorm water. Instead, storm water iscollected and conveyed as quickly ande fficiently as possible. This processdelivers urban pollutants such as sedi-ment, hydrocarbons, metals, bacteriaand fertilizers to streams, rivers, andlakes.

Low impact development minimizesthe amount of impervious surfaces andmitigates the impact of necessaryimpervious surfaces. There are a vari-ety of conservation practices that worktogether to mitigate these effects, suchas pervious paving, rain gardens,bioretention cells, bioswales, nativelandscaping and soil quality restora-tion.

A bioretention cell man-ages runoff from theimperviousness of a com-mercial parking lot.Abioretention cell is a lowimpact developmentp ractice because it allowsra i n water to infiltra t e,minimizes flooding andprotects water quality.

Low Impact Development

Low Impact Development (LID)

The USDA is an equal opportunity provider and employer.

More Information aboutLow Impact DevelopmentFind additional information about LID byvisiting the following websites:

www.lowimpactdevelopment.orgwww.iowastormwater.orgwww.iowasudas.orgwww.cwp.orgwww.stormwatercenter.net

Key Principles of LIDEnvironmental protectionNatural features, such as wetlands, woodlands, and stream buff e r sare protected. By preserving these features, natural drainage pat-terns can be identified and used as green infrastructure, biodiversityis retained and wildlife habitat is protected.

Storm water management Rather than flowing off site, water is directed to infiltration-basedstorm water management practices and absorbed on site. Keepingwater on site reduces pollutant loads, moderates peak stream flowrates and volume, and enhances base flows.

Community characterIn residential settings, homes typically open up to open space andfeature recreational trails. Native landscaping provides aestheticvalue, adequate storm water conveyance, distribution of water flow,and filtration of pollutants.

Modular paver blocks serve as a paving alternative in thiscommercial parking lot in West Des Moines, Iowa. Perviouspaving is a low impact development practice that allowsrainwater to infiltrate, minimizes runoff and flooding, replen-ishes groundwater, and protects water quality.

Benefits of Low Impact Developmentto residents:• increases community character• improves quality of life• more access to trails and open space• p e d e s t r i a n - f r i e n d l y

to developers:• reduces land clearing and grading costs• reduces infrastructure costs (streets, curbs, gutters, sidewalks)• increases lot values and community marketability

to communities:• balances growth needs with environmental protection• reduces infrastructure and utility maintenance costs

to the environment:• protects environmentally-sensitive areas• increases wildlife habitat by preserving trees and vegetation• protects water quality by reduciong pollutant loads• reduces stream bank and channel erosion by reducing peak

flows and moderating the frequent bounce associated withlower intensity storms

• reduces flooding potential