Drinking Water Protection Resource Center

Onsite Wastewater Resource Center

Stormwater Management Resource Center

Publications



Rhode Island Stormwater Solutions is getting a new look in 2013!

Stay tuned.

 

Site Assessment Mapping

 

Rapid Site Assessment This method can be used as a general overview of site-level constraints. There are two levels of site review possible with this method; the first uses internet-based mapping resources, while the second requires the use of GIS software. The first level is ideal for a quick overview of the site's potential constraints. The second level provides more detailed analysis.
GIS and Conservation Development
Information on using GIS in conservation development is currently being developed in cooperation between RI NEMO and RIDEM.


 

Rapid Site Assessment

 

What Is It?
Rapid Site Assessment (RSA) is a method that provides a preliminary review of a parcel of land, using readily available computer-generated maps and other data. The goal of RSA is to offer tools that incorporate basic information about site features and constraints to anyone making land use decisions, with the intention that the information can be used in the development review process as early as possible, specifically during the pre-application stage.

Land developers, planners, designers and local board members will find this approach simple and useful. It is especially valuable for compact designs such as cluster zoning and conservation development. For these alternative developments, thorough site assessment is needed to identify areas for concentrated development, areas for protection of critical resources, and marginal areas to avoid or minimize impact.

While Rhode Island towns typically require some sort of site assessment before development, many times, important site information is discovered late or it is not presented in a consistent format, making it difficult to review. By gathering as much information as possible early in the development process, the Rapid Site Assessment technique enables reviewers to focus on land capabilities and protection goals before considering lot configuration, road layout, and drainage.

The Importance of RSA
The site review process undertaken in many Rhode Island towns has limitations. First, the quality of site assessment information varies widely depending on the applicant. Not all applicants have the same resources, creating disparity in how different projects are reviewed. Incomplete applications are a consistent problem; reviewers frequently do not receive information soon enough to assess the site thoroughly, early in the process, when changes are less expensive to make. Even when site information is provided in a timely manner, it is not always put to best use in analyzing land suitability and design because of map incompatibility or lack of structured early review procedure. There is also no consistency among town requirements, making it more difficult for developers and engineers to know what to expect. In addition to these administrative issues, marginal sites that were once considered unprofitable due to site constraints are now being developed as growth pressures drive up land costs. More intensive review procedures are necessary for these more sensitive lands.

RSA Is Compatible With Other Methods
The ideas and procedures outlined in this document are not new. They are based on long-established principles in planning, landscape architecture, and soil science. The Rapid Site Assessment technique simply takes advantage of information sources that have become much more widely available due to the evolution and availability of Geographic Information Systems (GIS) technology and data. This procedure is fully compatible with the four-step conservation design technique advocated by leading landscape architects and planners and widely used as standard practice in creative land development design. By suggesting two or more alternative development sketches at the early pre-application stage, the process encourages creative and environmentally-sensitive design while highlighting the need for flexibility and discretion in regulations.

How Does RSA Work?
The analysis is divided into two levels. The Level One Analysis uses a simple photocopy of the plat(s), a USGS Topographic map, and a series of resource maps readily available through the Internet. Individuals with limited information resources and no GIS experience could complete a Level One Analysis entirely on their own. The Level Two Analysis requires more detailed resource data from either Geographic Information Systems (GIS) or hardcopy sources, along with a basic site survey and proposed development concept sketches. This more advanced analysis requires a moderate to high skill level and is more appropriate for professional planners or engineering firms. However, with the advent of Internet Map Server (IMS) technology, detailed data layers and customizable maps are easily obtained and can be used to complete a Level Two Analysis.

Benefits of Rapid Site Assessment

  • Allows the evaluation of the relationship of the parcel to the surrounding site from a town or watershed perspective.
  • Aids in identifying townwide protection priorities using planning-level information and town plan goals.
  • Helps avoid premature decisions that lock the developer and Planning Board into one design before all options have been evaluated. Early assessment and consensus on reasonable design options helps avoid backtracking (and associated engineering expense) to evaluate new options or redesign at later stages.
  • Identifies general site suitability for development. Identifies areas with severe development constraints where construction costs are higher as well as sensitive areas where disturbance should be minimized to reduce environmental impact.
  • Identifies most suitable areas for Individual Sewage Disposal Systems (ISDS) and stormwater controls and helps focus field investigations.
  • Provides a clear understanding of constraints and opportunities in user-friendly, visual format as basis for reaching agreement on preferred options.
  • Documents factors considered in selecting design; enables town to show basis for board decisions in a user-friendly visual format.
  • Takes advantage of readily available high resolution, extensive RIGIS database. Data are readily available at both town and watershed scale, fostering watershed- based planning.
  • Provides recent land use data (1995) that is more current than most town maps (1988).
  • Provides access to data such as DEM Natural Heritage Areas that may not be available at the town level.
  • Provides enhanced data and standardized formatting such as soil hydrologic groups.

Limitations of Rapid Site Assessment

  • Not all consulting professionals currently use GIS. However, the same process can be performed with large format hard-copy maps such as those being produced through the DEM Greenspace Project or the RI HEALTH Source Water Assessment Program.
  • RIGIS information is useful for concept-level planning only. Onsite surveys are needed at the later pre-application phase, to include:
    1. high-intensity soil survey to provide accurate boundaries and classifications
    2. wetland edge delineation and vernal pool mapping
    3. topography (2 ft. contours)
    4. vegetation mapping
    5. other natural, historic, archeological, and scenic resources as required by the town

 

Level One Analysis


This first level of analysis can be performed by anyone with access to the Internet and a color printer. It can also be done using conventional hard-copy maps, but this can be more difficult because these maps come from many diverse sources at different scales. Townwide maps were used for the case study discussed below and shown above because the development site was well within town borders. Depending on site size and location, you may want to use either town or watershed map format (or perhaps both).

These maps are useful for basic early review of any project. They enable the developer and local decision makers to:

  • Visualize how the project site fits in the surrounding environmental and social context of the community, a type of analysis that is otherwise often limited to a fuzzy location map;
  • Review features beyond the project boundary that might otherwise be overlooked, especially for projects located near town borders;
  • Better address town goals for the general project area before focusing on specific features of the site.
    Although resolution of the maps used here is limited, the fact that they are free and readily available makes them a valuable resource as long as their limitations are understood.

How To Conduct a Level One Analysis

Step 1. Locate the approximate boundaries of the proposed site on plat or through materials provided by the applicant. Note landmarks such as road intersections and streams that will help you locate the site on the other maps.

Step 2. Visit RI Critical Resource Atlas Web Site (http://www.edc.uri.edu/riatlas/) and download maps for printing. Maps on the digital atlas are obtained by selecting the town or watershed you want, and either clicking the map of interest (Town Atlas or Watershed Atlas) and then choosing the town from the associated list, or choosing the name of the town or watershed on the drop-down menu. Once you choose the town or watershed you want, it will move to another page where you need to scroll down to see the maps. Choose the map and format (8.5" x 11" or 20" x 20") you want, and after the map appears, you can either print it or save it to your hard drive for future use. To save it to the hard drive, right-click and choose "save image as".

Step 3. Once you have printed the maps, locate the site and pencil-in the approximate site boundaries on each map. Each of the map types are listed below with findings for our site example.

In addition to these maps, use a USGS Topographic (1: 24.000) map to become familiar with the terrain. Topographic images are available from USGS or the RIGIS web-site (http://www.edc.uri.edu/rigis-spf/rigis.html). In the RIGIS website, click on the map for USGS Quad Data or scroll down to the town of interest under the map for Quad Data. Pick the town you are interested in and then scroll down the page to view available maps. Under “Raster Images” there are usually two choices, both for USGS 7.5 minute Topo Quad. Choose the file associated with “USGS 7.5 minute Topo Quad” by clicking on the zipped file (link to the far right in the table) and then save to your computer. The file is in tiff format and can be viewed in most photoediting programs as well as by importing into wordprocessing software. The file will have to be unzipped before viewing and printing.

About the RI Atlas Website
The RI Atlas provides pre-made GIS-bases maps for both towns and watersheds. These come in 8.5" x 11" and 20" x 20" formats that can be viewed online, printed, and downloaded. Once maps are downloaded, they can be brought into documents for reports or presentations. One technique to provide larger visuals with small-format color printers is to use the 20" x 20" format and crop it (in the word processing or presentation program) so important sections can be printed larger for visibility. If you choose this technique, be sure to print out the entire map in the letter-size format so you can analyze context.

There are several advantages to using the RI Atlas. First, it is easily accessible and covers all Rhode Island Towns and watersheds. Secondly, when a project is close to or straddles a town boundary, you can download consistent maps for both sides of the boundary. The atlas also has good soil hydrology information, that is not directly available on RIGIS, as well as information on rare species habitat. It is important to note that the rare species habitat information has not been updated in several years, so it is still important to contact RI Natural Heritage Program for more up to date information as the development project moves forward.

A Note About Scale in the Level One Analysis
Level One Analysis uses data at its intended scale or smaller, avoiding the scale-error problem, but providing only a very crude overview. This means that if you use the data source provided for the Level One Analysis, and mark your development parcel on this map, that there are no problems with zooming into a map too closely so that it appears the data is more accurate then it really is. When completing the Level Two Analysis (discussed below), using interactive maps, often you are zooming into the data at a finer scale than the data were intended for. This provides a more detailed picture than Level One Analysis, but remember - the data are not necessarily accurate at this scale. All site characteristics should be confirmed through groundtruthing. More information on scale can be found on the Mapping Basics page of this website.

 

Level One Case Study
Using a 300-acre example site in Hopkinton RI, this case study was completed using the Level One Rapid Site Assessment Method. Each map is shown with basic information on the map. Click on the thumbnail of the map to see it in a larger view.

Overview- This map provides a clean base to locate the site. It also shows proximity to facilities such as schools, libraries, and other municipal services. In our Dye Hill road example, we found that the site abuts a large protected area. One priority may be to preserve open space on the site to foster greenway linkages and preserve wildlife habitat.
Forests and Wetlands- This map begins to give an idea of ground cover and wetlands issues on a site, and how these resources relate to surrounding context. It is important to note that at this scale only large wetlands, ponds, and streams are shown. Although it is based on wetlands maps where the minimum wetland size is quarter-acre, these smaller wetlands will not appear because of the small printout size. Consult USGS maps and large format hard copy wetland mapping (level 2) if possible. In our Dye Hill Road example, we see that the site is mostly forested, with some fields or brush. What are the development opportunities and constraints related to these types of ground cover?
Land Use- This map lets us see what types of development and land cover surround the site. Residential development is broken up into different densities, giving an idea of the character of the surrounding area. In our example, we see that our site is mostly deciduous forest with a bit of mixed forest to the northeast. There is some agriculture (not necessarily active) towards the front of the site. That section of Dye Hill Road has fields on both sides. How will development affect the character of this stretch of roadway?
Groundwater Resources- The mapped groundwater aquifers are areas of significant volume of groundwater, sometimes referred to as the groundwater reservoir. Recharge areas show the drainage region that provides rain infiltration into the aquifer. Wellhead protection areas provide direct groundwater recharge for public wells. The wellhead protection area for larger public wells (yielding greater than 10 gpm) drilled in outwash (sand and gravel) deposits are delineated using a groundwater flow model which tends to produce an irregularly shaped wellhead delineation. The wellhead protection areas for smaller wells and those drilled in bedrock are delineated using a standard formula which results in a circle with a radius of 1,750 feet. Because all land use activities in these recharge areas affects the quality of the underlying groundwater, development occurring in any of these resource areas requires special management. Our site off Dye Hill Road lies partially in a wellhead protection area. It does not lie over any aquifer or recharge area.
Biodiversity- This map is a very convenient source for rare species habitat locations along with the same protected open space as the overview map. There are no designated rare species areas within our site. There is one area just to the nortwest, and another downstream on the Wood River. How will cumulative development in the upper watershed affect this rare species habitat?
  Coastal Wetlands- Usually, this map breaks coastal wetlands into different categories. Although it would be very valuable for analysis in a coastal community, it was not useful in our example because Hopkinton is landlocked.

Soil Hydrology- Soils are mapped by hydrologic group (permeability) and depth to water table. Areas with restrictive and high water table soils have significant constraints and management issues because of the likelihood of septic system failure, seasonal flooding, and pollutant runoff to surface waters. Excessively permeable soils increase pollution risk to groundwater, but are also valuable for recharging groundwater. The Dye Hill Road site is mostly in dry well-drained soils, but has several areas of moist (seasonally wet) soils running through its center. What is the best way to design the site with soil conditions like these?

Note that the color scheme for soil hydrologic group and depth to water table has been updated, other maps of the same data may exhibit a modified color scheme; this does not affect the data.

Watershed Sub-Basins and Surface Water- Drainage basins are the area of land that drain into rivers, streams, ponds, and estuaries. This map is useful for locating a project in the sub-basin, but does not delineate watersheds within the sub-basins. For our Dye Road site example, we see that the site is in the Wood River Sub-basin. From the streams and ponds on the map, we can see that the site is directly upstream from a large pond. The USGS Topographic map reveals that it is Locustville Pond and our site is within the Pond's watershed. One thing that stands out is that there is a stream shown on the USGS Topo running right through the center of the site that does not appear on the RI Atlas maps. This is a minor tributary to Brushy Brook, and only major streams were mapped in the RI Atlas. This emphasizes the usefulness of the USGS Topo map. Since only major basins are shown in the RIATLAS, the local subwatershed must be delineated using elevations from a USGS topographic map, as we have done here. What management practices can be used to protect ground and surface water quality?

Other publications provide information on existing water quality in the pond. In this case, we referred to the Pawcatuck Watershed Report (Pawcatuck Watershed Partnership 1998) and found out that Locustville Pond is Class B (habitat, recreation, aesthetic value- not a drinking water reservoir) but is threatened for aquatic habitat by noxious aquatic plant growth caused by non-point source pollution. Monitoring data collected by Watershed Watch citizen volunteers documents that the pond tends to be enriched with nutrients (URI 1998). Brushy Brook, the small stream that runs through the southern portion of the site, is Class A (highest quality) and is fully supporting these uses in this area.

How much of the Locustville Pond area has been developed and with what use?

USGS Topographic Image``



 

Level Two Analysis

The Level Two Analysis is very similar to the conservation mapping process. The site is evaluated with a greater level of information than what is available under the Level One Analysis. Under this Level Two Analysis, project specific maps are produced, generally using GIS software. These maps should have a greater level of detail than those produced under the Level One Analysis. Ultimately, the Level Two maps are reviewed to determine areas that should be left in a natural state and those areas that constitute the best development sites. This should be an iterative process; as the process progresses with the involvement of both the developer and municipality, updated and more accurate information should replace initially-available data, further refining the development plan.

In most towns, all of the site features mapped in the Level Two Analysis are already standard requirements of a subdivision submittal. (In fact, the applicant may find it more cost effective to provide the general site information as GIS overlays.) The information is available, but not always fully evaluated before proceeding to detailed review of road layouts. More thorough attention to site features can be useful in reaching agreement on areas to focus development and areas to protect.

The Need for Site-Specific Information
GIS coverages provide screening level data that is useful only in the earliest pre-application and concept review stages. Site-specific information such as two-foot contours and verified wetland edge are needed for accurate site assessment. Many project consultants agree that obtaining this data sooner rather than later is well justified given its importance in road layout, siting buildings, designing stormwater drainage systems, and siting septic systems. In addition, up-to-date vegetation surveys, location of stone walls, and identification of other unique natural, cultural, historic, and archaeological resources is required in early site design.

Two other types of analysis not typically required but that provide essential data in early site design are: site-specific soil survey mapping and vernal pool mapping. Vernal pools provide important habitat for increasingly threatened salamanders, frogs, and other amphibians and reptiles, but they are not protected by state regulations. These temporary pools can easily be identified and mapped by wetland consultants hired to verify the presence and extent of wetlands.

A site-specific soil survey is necessary to verify that state-mapped soils are accurate at the site level. The RI Soil Survey has been proven to be remarkably reliable, but it is a planning tool, not intended for site level analysis. In addition to the problem of scale (the boundary line between two soil types on the map can vary by 40 feet in the field), soil complexes occur that include different soils types with dramatically different characterstics. Because these soil types occur together in association, they can only be mapped accurately through a site-specific survey.

Recognizing the value of better soils information, the Rhode Island Department of Environmental Management (RIDEM) has revised regulations for onsite wastewater treatment to require that licensed site evaluators with training in soil science be permitted to determine septic system suitability. In addition, RIDEM is moving towards a more soils-based approach to site assessment that will reduce reliance on perc tests and increase use of soils data to estimate water table elevations. Given the importance of soil evaluation in septic system suitabiity determinations, it makes sense to rely on accurate soils information to first identify potential areas for building sites, septic systems, and stormwater drainage systems. Site-specific soil surveys are especially important for towns with soil-based zoning but are not routinely required.

Recommendations for Level Two Analysis

  • For major subdivisions and other large projects the municipality could require the developer to assemble coverages used in the Level 2 analysis and using these, demonstrate how the proposal achieves town goals for the area and minimizes potential impacts. At a minimum, the town should require the applicant to completely present the site analysis information before any road layout. The site analysis should identify optimum sites for development, critical areas to be preserved, and marginal areas where disturbance will be minimized to avoid impact. The findings of the site analysis can then be used to develop at least two concept sketches that can be used to select conventional vs.alternative designs.
  • Towns should consider requiring vernal pool identification whenever wetland edge delineation is specified. This would include pool mapping, and potential travel areas or hydrologic connections to other pools. Since vernal pools are not regulated by DEM and pool boundaries are not verified by DEM, the town may have to hire their own wetland scientist to verify vernal pool locations.
  • For large projects or those in sensitive areas, the municipality should require a site-specific soil survey, conducted by a qualified professional soil scientist, certified by the American Registry of Certified Professionals in Agronomy, Crops, and Soils (ARCPACS).
  • For large projects, those in sensitive areas, or those where the town requires and environmental assessment, results of detailed site investigations such as wetland and soils mapping, vegetation types, and other site features would be incorporated into a much more accurate overlay analysis.
  • The Natural Resources Conservation Service, in cooperation with State agencies, municipalities, URI, and the Southern New England Soil Science Society, should consider developing consistent standards for site-specific soil surveys for the southern New England region. These could be adapted from standards currently used in northern New England. In addition, these groups should consider standardizing data requirements for site review as guidance for Planning Boards, such as those used by the State of New Hampshire.

 

How To Conduct a Level Two Analysis with Level Two Case Study

Field investigation
The reviewers and applicant should conduct a field investigation to be sure that submitted site information is correct. The reviewers should:
1. Walk the site to identify important factors that were missed in the initial data gathering.
2. Note large trees and other distinctive vegetation for preservation.
3. Envision road and house placement and accompanying impacts.
4. Evaluate the proposed access point and width of the entrance (sight lines, impact on wetlands and stone walls).
5. Interview neighbors for their concerns and point of view.

This is an excellent opportunity to reinforce information learned from the maps, as well as to develop map reading skills in the field and identify any areas that have changed or were not included.

Assembling data and maps
Most data necessary for this analysis are available on the RIGIS website. RIGIS data will need to be downloaded and, using a GIS software package, manipulated to produce the series of maps exhibited below. Information on recommended layers to use in map production is available in the document Site Assessment Mapping for Development. Detailed descriptions on how to produce the necessary maps are not provided here.

Each of the required maps is exhibited below along with a basic description of the map components and key questions to ask regarding the map information. The maps presented are for a site in Hopkinton, RI.

Topographic Features- This image will show the general contours of the land.

Questions to ask:
· What is the general lay of the land?
· Which areas will be most disturbed through grading?

In the Dye Hill Road site, there are some substantial slopes (8-15%) and stony soils, with some rock outcrops (CeC), increasing construction cost for roads and foundations.

Orthophotography- An aerial photograph at the same scale as map data provides excellent site orientation. This one is from ortho.edc.uri.edu.

Questions to ask:
· What is the general lay of the land?
· How is the land currently being used?

 

Soils Constraints- The Soil Survey of Rhode Island is a rich source of development constraint information. General soils data allows determinations of specific areas of the site that may be unsuitable for development. The soil constraints map can be produced using the general soils layer color scheme located under the References section of this site. Additionally, erodible soils can be highlighted if they are a problem for your site.

Questions to ask:
· Where are the hydric (wetland) soils (Hydro-Group D)?
· Where are the high water tables (Hydro-Group C) soils?
· Are there restrictive layers present (Hydro-Group C)?
· Where are the best soils for ISDS placement (Hydro-Group B)?
· Where are excessively permeable (Hydro-Group A) soils?
· Are there any very stony soils or rock outcrops?
· How do the various water table depths affect suitability for ISDS and storm drainage structures (see reference table below)?

Facility Minimum Separation Distance from Water Table
Septic System Drainfield: 24"
Drainage Swale: 24"
Storm Water Pond: 12"
Infiltration Basin: 36"
Source: RIDEM Regulations

The Dyer Hill Site is primarily well-drained hydro-group B soils (Charlton-Canton CdA, ChB, ChC, ChD), with some restrictive high water table C soils (Ridgebury Rf) along the tributary of Brushy Brook. Some high water table B soils (Sutton SuB) connect fingers of C soil, creating a substantial extended drainage network. There are some excessively permeable A soils (Hinkley HkC) near the site entrance along Dye Hill Road that may pose a threat to groundwater if improperly developed. One constraint that particularly stands out is that almost the entire site has highly erodible soils because of the steep slopes and soil composition. Erosion and sedimentation controls should be carefully applied and monitored throughout construction. Site designs that limit disturbance and minimize impervious cover will be most effective in avoiding erosion impact. See the Understanding Soils section of this website for more detail on analysis methods and management practices.

Hydrologic Features- This map should indicate drinking water reservoir watershed, wellhead protection areas, ponds, streams and any other water resources.

Questions to ask:
· Is the site in a drinking water reservoir watershed, groundwater protection overlay zone, aquifer recharge areas/ reservoir, or wellhead protection area?
· Where are surface water bodies located (streams, rivers, ponds, lakes)? How do they function in natural site drainage?
· What watershed is the site in (sub-basin level)?
· Are there any rare wetland types on the site (i.e. bogs, fens)?
· Are there vernal pools on the site (must be varified in the field)?
· Is the site in a floodplain?

As noted above, a tributary to Brushy Brook, which feeds Locustville Pond, runs through the site. There is a small pond on the easternmost tributary. Wetlands include deciduous forested, shrub-scrub, a marsh or wet meadow near the site entrance, and a shrub-scrub bog to the west. Bogs in particular are very sensitive to disturbance and this should be considered during construction grading and ISDS siting. Note that there are wetlands on the site that do not show up in the RI Atlas maps used for the Level one analysis. The RI Atlas only covers large wetlands, but the RIGIS wetlands data (available on the web) includes wetlands ¼-acre and up, classified by type.

Some of the southern end of the site lies within a Community Wellhead Protection Area (serving year-round residents with at least 15 connections or 25 residents). This area coincides with a band of excessively permeable outwash soils. A small amount of the site near the entrance along Brushy Brook is in Flood Zone A.

Open Space- Open space protected by various agencies such as the municipality, Audubon Society and the State are indicated.

Questions to ask:
· What types of open space are present on the site (i.e. open meadow, deciduous forest, and coniferous forest)?
· Is the open space contiguous or fragmented? Is it possible to connect the open space with the larger regional scale?
· Greenway Linkages: Will the designated open space be connected to a larger greenway network? Will wildlife migration paths and access to water be contiguous?

Our site has deciduous and mixed forests, brush, and small clearings. It is contiguous with two large sections of Arcadia Management area, creating a forested connection broken only by Woody Hill Road and associated low density residential development. The State Greenway Corridor runs southwest of the site but there is no direct connection (See also Level 1 Land Use and Biodiversity).

Scenic Views to and from Property- Scenic views are indicated by the State as well as determined during site visits.

Questions to ask:
· Are there scenic views from or into the site?
· Are there historic or natural features that can be used as focal points (i.e. rock outcrops, historic trees, stone walls, coastal views)?

The area all along Dye Hill Road has been designated scenic by the RI Department of Environmental Management.

Historic and Cultural Resources- The location of stone walls, historic cemeteries, Native American Burial Grounds, historic homes, and farms should be indicated. This information can be partially found on the RIGIS data, but should also be determined during a site visit.

Questions to ask:
· What historic or cultural resources should be preserved?
· What historic or cultural resources must be preserved based on State laws.

According to RIGIS data, there are no archeological or historic resources on the site, but these data are limited. There are several candidate and registered historic districts to the south. A detailed survey is needed to identify stone walls and other historic and cultural resources.

Rare Species and Other Wildlife Habitat- This information could come from the Town's Conservation Commission, DEM Natural Heritage Program, or The Nature Conservancy. This information is generally mapped with historic and cultural resources information.

Questions to ask:
· Are any rare species or protected wildlife habitat on the site?

Two DEM Natural Heritage Program rare species areas lie north of the site, one along Woody Hill Road and the other within Arcadia Management Area. There is another rare species area south of the site along the Wood River. Only DEM and RIGIS coverages were used in this example, but another important resource is GIS data from the EPA Rhode Island Resource Protection Project.

Synthesizing the Data
Some general questions that emerge from a Level Two Analysis are:

  • How does this site fit into the larger landscape?
  • How will this subdivision impact neighboring sites?
  • Does it conform to the goals of the Comprehensive Plan?

After considering all the issues, the board or committee should work with the developer and consultant to:

  • Delineate priority areas for preservation and desirable areas for development.
  • Consider potential impact to resources on the site and in the surrounding area.
  • Determine the point of entrance and preliminary road layout.
  • Determine areas where shorter road layout, reduced roadway width, and alternative paving materials may be used to reduce pavement.
  • Integrate stormwater controls into design, preserving well-drained areas for infiltration; determine where non-structural stormwater measures can be used for roadways and on individual lots.
  • Determine the degree of grading on the site (minimize where appropriate).
  • Determine the type of ISDS (conventional or innovative) appropriate for the project. For example, some design tradeoffs may involve placing part of a house lot in seasonally wet soils. Innovative drainfield design or placement can help avoid an unsightly mound system.
  • Determine most effective erosion control measures before, during and after construction to minimize impact.


The purpose of this step is to identify the most appropriate areas for development and preservation, determine mitigation for marginal areas that will likely be developed, and assess whether creative/flexible development techniques will further Town goals expressed in the Comprehensive Plan. If reviewers determine that creative/flexible development techniques could provide a significant benefit and are provided for somehow in the zoning ordinance, the site analysis process described above lends itself directly to the four-step Conservation Subdivision design process advocated by planners such as Randall Arendt, Dodson Associates, and others (Arendt, et. al. 1994).

For the Dye Hill Road example, Dodson Associates designed a conservation subdivision concept sketch based on the Level Two Analysis described above, seen here with topo or soils.

 


 

GIS and Conservation Development

Information on using GIS in conservation development is currently being developed in cooperation between RI NEMO and RIDEM. It is anticipated that GIS data layers with appropriate legend information will be available to streamline the procedure to prepare maps under conservation development in the near future. Additionally, an ArcExplorer project with the same data will be made available for use by those without ArcView licenses.

This data is anticipated to be available early in 2007 and will be made available on this site.

       

Copyright 2006 URI Water Quality Program 
        URI Cooperative Extension logo