The Low Impact Development Center describes LID as “an innovative stormwater management system approach with a basic principle that is modeled after nature”. LID minimizes the impact of development on the local watershed. As land is developed, runoff patterns change due to the addition of impervious cover or a modification to areas of open green space. Planned landscape features can help address stormwater and the way it flows through a site. Typical components of LID include vegetation, pervious pavements, and bioretention systems.
Some examples of bioretention are buffer strips and stormwater wetlands which detain water long enough for infiltration and pollution removal to occur. Low Impact Development (LID) controls the first bit of runoff in a rain event and provides a high level of water quality treatment due to filtration provided by runoff interception techniques.
Some Best Management Practices (BMPs) used in LID are permeable parking and green roofs. Permeable parking has a lower impact than other developments who use a traditional asphalt design for parking lots because the permeable design allows water to seep into the ground through exposed soil or gravel.
Green roofs can absorb and store rainwater in the vegetation that is placed on a prepared rooftop on a new or existing building. Because of the multitude of design options set forth by the Low Impact Design Center, LID can be used in most applications by analyzing the characteristics of a particular development area. LID concepts vary for each site since each development is different. Mostly developers just need to maintain natural drainage patterns and mimic natural hydrology on site and minimize the impact the development has to surrounding sites.
Not only are there benefits to surrounding watersheds in terms of runoff flows, but LID also enhances the local environment, protects public health, and improves community livability. A nice bonus is that it saves developers and local governments money. Oftentimes, LID provides an economic advantage compared to traditional construction and development of new and existing sites by reducing maintenance requirements and clearing or paving costs.
Elements of SmartGrowth
There are 10 elements that define Smart Growth in coastal communities. These guiding principles are based on experiences of successful communities and their characteristics. Many of these elements intertwine and overlap when planning a sustainable community. Through Smart Growth, communities are encouraged to mix land uses, take advantage of compact design, provide a range of housing choices, create walkable communities, and foster distinctive, attractive communities. Preservation of open space and critical environmental areas, development toward existing communities, and a variety of transportation options is also suggested. Development decisions must also be predictable and fair, and community and stakeholder collaboration should be encouraged.
Mix use developments encourage residents and visitors to walk or bike between destinations by mixing these buildings or services in together instead of isolating residential from commercial or civic areas. This element directly ties into creating walkable communities and taking advantage of compact designs. When possible, it is best to place water-based and non-water-dependent developments close together to provide a basis for more sustainable growth and the opportunity for both residents and businesses to thrive. Compact design also uses less land so more natural areas are preserved. Compact design also can reduce runoff, flooding, and stormwater drainage needs by leaving undeveloped land to absorb rainwater. In this element, it is helpful to employ Low Impact Design practices that will vary based on the specific site. When in a coastal community it is very important to provide housing opportunities for not only permanent residents, but for seasonal visitors as well. When affordable housing options are available, pollution from commuters is lowered and congestion on the roadways is minimized. Developing a variety of housing options is easy when developing mix land use areas and compact building design.
Lastly, predictable and fair development decisions can encourage increased collaboration between stakeholders and the community. To keep the process fair and transparent, regulatory agencies must coordinate with each other and the public. An example of an effective policy framework that encourages just decisions and collaboration would be one that includes easily accessible information for the planning and permitting processes which may be provided to the community through an app or website. This in turn holds the regulatory agencies more accountable and builds trust with the community. When the public holds enough information to form their own opinions on a development they are encouraged to voice their concerns or praise of the proposed project. This ensures that all stakeholders are given a chance to be heard.
Tools for Watershed Protection
There are 8 tools laid out in the EPA’s watershed academy online. These tools can be used together to improve sustainability of watersheds on a subwatershed basis. The first, and arguably most imperative tool at this point in time, is land use planning. Redirecting development and preserving sensitive areas are the goals of land use planning. It is important to maintain, or ideally, reduce the impervious cover within a watershed. When determining specific land use planning goals, the first step is to classify a subwatershed by the amount of existing impervious cover. Impervious cover should be maintained below 10%. Once impervious cover hits 10% the subwatershed is classified as a degraded system. A watershed with 25% impervious cover is classified as a non-supporting stream.
A non-supporting stream might exhibit high bacterial levels, poor biological diversity, or eroding banks. Part of land use planning takes into consideration land conservation. The EPA suggests that critical habitats, aquatic corridors, hydrologic reserve areas, water pollution hazards, and cultural areas be conserved in a subwatershed. Conservation easements are are a technique used to conserve land by passing part of the interest in a property to an organization or other entity that prevents the property from being developed. Land conservation is the responsibility of both government and individuals in the community.
In cases where wetlands need to be protected from the impacts of close land use aquatic buffers may be used. Benefits of aquatic buffers are only achieved if and when the buffer is well planned, designed, and maintained. Better Site Design can conserve natural areas and limit pollution run off from developed sites. Parking lots and residential streets make up about 65% of total impervious cover. If better site design was considered early on in design of the site, some of this unnecessary impervious cover could be eliminated. Open space design is a popular technique that leaves a larger portion of a site open instead of needlessly developing large lots.
When construction is occurring, and after when soil is settling, measures must be taken to reduce sediment loss. If open space design is used, erosion is automatically reduced due to the minimization of land clearing. The use of silt fences or sediment basins can also mitigate the effects of land development on the surrounding watershed. The key to an effective erosion control plan is proper installation and timely maintenance. Stormwater management is particularly important on development sites in order to compensate for the changes to hydrological patterns in the area due to new and existing development. Good stormwater management techniques maintain groundwater quality, reduce pollutant loads in rain events, prevent flooding, and safely transport extreme flood flows. Some BMPs to be considered are grassed channels, constructed wetlands, and bioretention ponds.
Not all discharge is due to stormwater or rain events. Non-stormwater discharges include septic systems, sanitary sewers, and other miscellaneous discharges such as runoff from agricultural sites. Almost a quarter of septic systems nationwide are estimated to be failing or not operating as designed. These failures can be detrimental to our watershed when waste is discharged into the groundwater supply. Promoting the protection of our watersheds is vital to the success of government programs. The six programs that should be considered are Watershed Advocacy, Watershed Education, Watershed Maintenance, Pollution Prevention, Indicator Monitoring, and Watershed Restoration. Once the community is aware of what is at stake, their involvement will help foster a successful ongoing watershed management program.
Best Management Practices That Facilitate Sustainable Stormwater Management
Runoff from storm events is a principal contributor to our watershed pollution concerns. Rain events cause flows through impervious areas, such as parking lots, that pick up debris and other pollutants along the way to our water bodies. Therefore, a sustainable stormwater management system is vital in protecting our watershed. There are many approaches that homeowners and developers can take to lessen their impact on stormwater management. The practices that are often recommended due to a history of success in sustainable stormwater management are known as Best Management Processes, or BMPs.
In both new and existing developments, installing porous pavement in parking lots/driveways can allow water to infiltrate back into the ground instead of running off and contributing to erosion and pollution. It is also important to design with protecting natural areas in mind. Planning for open spaces, or areas that are purposely not developed, protects natural areas and gives the flows from rain events somewhere to go and be absorbed. Another approach that can slow down rainfall flows along with trapping pollutants is employing constructed wetlands on a site. When there isn’t land available to leave open spaces, green roofs can be a great alternative. Green roofs do not take up a large footprint at ground level, but they are able to filter, absorb, and detain rainfall by use of vegetation.
Around impervious areas, such as parking lots that have not yet been retrofitted as porous pavement, buffer strips can be designed to collect the flowing water or run-off. Grass lined channels are an example of a buffer strip that uses grass or vegetation to slow down flows and absorb some of the rain. To keep a sustainable stormwater management system, we must also work to control pollutants that are entering the water supply by running off in rain events. Individuals can help by picking up and properly disposing of pet waste. Developers can help by controlling erosion on construction sites.
Two common erosion control methods are silt fences and rip rap which help contain loose silt or soil to keep it from running off in heavy rainfall events. The local government on a city or county level can help by utilizing street sweepers to get debris from roadways and away from drainage areas that tend to become cluttered with bottles and snack wrappers. Sometimes practices will not be effective enough individually, but they may provide a vital function in a system when combined with others. As communities change, so will the preferred methods of stormwater management but as ideas evolve we will all need to play our part to avoid failure of our stormwater management systems.
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