Vulnerability Score

Ecological Vulnerability Scores by Census Block

Raw composite scores then need to be aggregated to a unit of analysis for easy comprehension and integration into planning. For the REF, the unit chosen was the Census Block. Blocks represent the most refined unit that the Census Bureau publishes spatial data for, offering a fine-grain neighborhood-level unit of analysis. FHWA’s Eco-Logical approach and relevant literature recommends aggregation of composite scores to units that have some ecological connection, are compatible and accessible by potential users, and can be integrated with existing plans and resource-agency products (Strayer et al., 2003). Census Blocks satisfy those recommendations as they are based, in part, on ecological boundaries, are publicly available and easily understandable, and they are commonly used in planning and agency reports.

The raw Ecological Vulnerability Scores are aggregated to Census Block level using the aerial interpolation method (Flowerdew et al., 1991). This method calculates scores for each block based on the amount of area each union polygon takes up in the block.

The above figure depicts the Census Block-aggregated Ecological Vulnerability Score map, with darker colors indicating higher scores (more potentially vulnerable blocks). Scores range from 0-42, with the 10 percent most potentially vulnerable blocks scoring between 16.4 - 41.2. The least potentially vulnerable 10 percent of blocks score between 0-5.8. Just over 45% of the blocks throughout the county have scores between 5 and 10 (45.7%), with significantly fewer blocks with scores between 10 and 15 (23.9%) followed by 6.1 percent of blocks with scores between 15 and 20. Less than 1 percent of blocks score in the 31-45 range (Figure 5). Among all 7,268 blocks in the County, the average score was 10.1, indicating that Champaign County has low levels of generalized ecological vulnerability.

The majority of highest scoring blocks (high potential ecological vulnerability) are within high-quality natural areas and waterways, including the riparian zones of the Sangamon River in Riverbend and Lake of the Woods Forest Preserves, CRP land to the north of Fisher, the Middle Fork River Forest Preserve, Kaskaskia Ditch near Sadorus, and the Embarrass River in the southeast corner of the County. An example of a block with high potential vulnerability is located just north of Homer, along the Salt Fork River (Block 4009, Tract 010800) (Figure 06). Block 4009 has several contributing features that make it highly potentially vulnerable. The block contains a recorded observation of the loggerhead shrike, an Illinois endangered species. Homer Lake Forest Preserve encompasses the entirety of the block, and the southern border crosses a Biologically Diverse Stream (Salt Fork River) as well as being within the 100-year floodplain. Within the urban core, consistently high scores of potential vulnerability can be found along the Boneyard Creek, and the Saline Branch as it winds north through Crystal Lake Park, Busey Woods, and the Urbana Country Club (all contributing Natural Areas & Parks and Rec. EVLs). Hydrology is present in all of the highest scoring blocks, indicating that the Ecological Vulnerability Score favors water-related resources as potentially ecologically vulnerable. Other common features throughout the highest 10% most potentially vulnerable blocks are high-quality natural areas, floodplains, and archaeological areas.

Only about a quarter of blocks in the highest 10% most potentially vulnerable group are within the Metropolitan Planning Area (MPA). Even fewer of those blocks with scores over 30 (very high potential ecological vulnerability) are within the MPA boundaries. Those blocks with very high potential vulnerability occur mainly along the Sangamon River in central and south Mahomet. Many low-scoring blocks (low potential vulnerability) fall within the Champaign-Urbana MPA, central Mahomet, and most of Rantoul. The majority of blocks have scores in the 6-10 range, right around or slightly below the median score (average potential ecological vulnerability). These blocks of relatively average potential vulnerability are distributed evenly throughout the County, but blocks scoring less than 5 (low potential ecological vulnerability) are mostly concentrated in urban areas.

Final scores indicate the combined potential for ecological loss and environmental review for a project in a given location. Urbanized areas tend to have fewer ecological resources that can be impacted, reflected in relatively lower scores of potential ecological vulnerability, compared to the rural land beyond the MPA. However, urban areas do have the majority of special waste sites, which are review-triggering but non-scored due, in part, to the potential for promoting ecologically damaging “greenfield” development outside the MPA (see Assumptions and Limitations). With the exclusion of special waste sites, the blocks with least potential for ecological vulnerability fall within the MPA, particularly along the northern border of Champaign-Urbana, around Marketplace Plaza north of Neil Street. Other clusters of particularly low potentially vulnerable blocks follow dense urbanization. Examples include Downtown Champaign, (particularly around the intersection of W Church Street and S Neil Street), Campustown between E. Green Street and E. University Avenue, (just west of the Healey Street detention pond), and by the Carle Foundation Hospital campus just east of Lincoln Avenue and W. University Avenue.

Assessing Potential Future Impacts

To assess potential future impacts of transportation projects, planners must consider both the most ecologically vulnerable locations and locations most likely to be developed. The MPA encompasses the Champaign-Urbana Urbanized Area as delineated by the U.S. Census as well as the contiguous land expected to become urbanized in the next 20-25 years (CCRPC, 2020). With urbanization, new transportation infrastructure is necessary to meet the needs of the residential, commercial, and industrial development that is sure to follow. The MPA boundary is a general predictor of transportation infrastructure expansion. Already, the 2015 MPA boundary has surpassed the area predicted by the 2010 Land Resource Management Plan, Contiguous Urban Growth Area. Therefore, assessing potential future impacts means considering the MPA in relation to the top 10% most potentially vulnerable blocks, identified by the Ecological Vulnerability Score of Ecological Vulnerability.

The MPA is not a static boundary and is certain to change with future Census results. However, regardless of the exact boundary, lands contiguous to the existing urban footprint will be developed in accordance with smart growth principles and environmental objectives and strategies of the 2045 Long Range Transportation Plan. Blocks with the top 10% most potentially vulnerable scores that are contiguous to the MPA face an added layer of threat, likelihood of development. To help plan for growth that meets LRTP 2045 Environmental Strategies 4, 18, 19, and 20, these areas of high vulnerability and high likelihood of development should be prioritized for protection to maintain the ecological integrity of the region. The REF Composite Score of Ecological Vulnerability is not prescriptive but should be used as a guide for future transportation development plans that may impact highly ecologically vulnerable areas in Champaign County. 

Low scoring blocks, such as the interchanges, highways described earlier indicate that existing transportation infrastructure is at relatively low risk for environmental impact and environmental regulatory review. The same is true of other transportation infrastructure, such as the Canadian National Railway running through the heart of Champaign, paralleling Oak Street. Large scale transportation projects, like highways and railroads go through extensive environmental review procedures. This work often, but not always, results in the projects being located in less ecologically vulnerable areas, or in designs that minimize impact. Existing transportation infrastructure should have their uses maximized before considering development into more vulnerable areas on the periphery to avoid environmental impacts and review. While review processes will likely be unavoidable due to Federal and state actions concerning highways, the Ecological Vulnerability Score map shows that future transportation projects should utilize existing infrastructure as much as possible, versus developing new infrastructure at new locations.

Using the Ecological Vulnerability Score

With the Ecological Vulnerability Score layer, planners can make a preliminary assessment of potential impacts (i.e. this trail will likely cause fill material to go into this stream or will require encroachment on the property containing a historic site). Similarly, as most of the resources considered are review-triggering, planners can use the final layer for preliminary screening to either avoid or reduce the likelihood of triggering environmental reviews. These initial impact assessments will be very general, and lack the technical backbone to satisfy regulatory requirements alone. However, documenting these early considerations can increase the likelihood of approval, and decrease the work and time needed to consider them down the road.

The REF Ecological Vulnerability Score can be integrated into both NEPA and IDOT environmental review processes at several points. CEQ regulations 40 CFR 1501.2 states that “Agencies shall integrate the NEPA process with other planning processes at the earliest possible time to ensure that planning and decisions reflect environmental values, to avoid delays later in the process, and to head off potential conflicts” (CFR, 1970). Subsection b.4(i) also states that agencies need to “advise potential applicants of studies or other information foreseeably required for later Federal action” (CFR, 1970). As listed in Table 1, review-triggering is a major criteria for EVL inclusion in the Ecological Vulnerability Score. By using the Ecological Vulnerability Score early on to evaluate potential project locations and compare alternatives, agencies can bring NEPA into the planning process as early as desired to help satisfy CEQ regulations. Similarly, 23 USC 135(f) paragraph (4) states that Long Range Transportation Plans (LRTPs), must include a “discussion of potential environmental mitigation activities and potential areas to carry out these activities, including activities that may have the greatest potential to restore and maintain the environmental functions affected by the plan” (USC, 1955). The Ecological Vulnerability Score informs which areas are best suited for mitigation activities. Areas with high scores are those with the most resources in need of protection, like floodplains and 303(d) List Streams. These areas simultaneously show where mitigation efforts could be targeted. Mitigation efforts can expand existing high-quality sites, like Nature Preserves and wetlands, located near potential projects to comply with all applicable mitigation guidelines.

At the state level, with the exception of special waste sites (which are included only in the Interactive Map), the majority of resources required by an IDOT Environmental Survey Request (ESR), and the Bureau of Design and Environment Manual (BDE) are included in the Ecological Vulnerability Score. In a Phase 1 Corridor Report, referencing the Ecological Vulnerability Score as a preliminary screening tool strengthens the case for why an alternative was considered but not studied. Overall, it can strengthen the entire decision-making process by allowing generalized spatial comparisons of environmental vulnerability throughout the region. Later on in the project lifespan, reviews may be necessary, but documenting evaluative use of the Ecological Vulnerability Score can demonstrate that efforts were taken to consider all practical and practicable alternatives to impacting the resources as listed in CEQ guidelines. Reviews aside, this tool allows for earlier consideration of environmental resources into project planning.

Integrating Environmental and Transportation Planning

Environmental analyses produced to meet the requirements of state and federal environmental reviews are too often disconnected from the analyses used to develop long-range transportation plans, statewide and metropolitan Transportation Improvement Programs, planning-level corridor/subarea/feasibility studies, or the Federal Transit Administration’s planning alternatives analyses (NCTCOG, 2011). As a Metropolitan Planning Organization (MPO), the Champaign County Regional Planning Commission (CCRPC) has developed the REF Ecological Vulnerability Score tool to encourage a more robust review and consideration of environmental impacts and to inform strategies to mitigate potential environmental impacts associated with transportation infrastructure.

The REF Ecological Vulnerability Score helps bridge the gap between environmental review requirements and the transportation planning process by aggregating important resources in a way that holistically informs decision-making. Use of the Ecological Vulnerability Score tool provides a snapshot of the ecological vulnerability of a geographic unit of analysis, offering comparisons between different areas across Champaign County. Scores identify areas that are either more suitable for transportation infrastructure or less suitable due to the presence of ecological resources, guiding planning decisions before initiation of any review process. This ability to consider ecosystems regionally goes far beyond the considerations made at the project-level. Incorporating the Ecological Vulnerability Score into projects and analyses allows for conservation and mitigation priorities to align with planned growth scenarios, resulting in products that can be carried efficiently into state and federal environmental review processes.

Composite Score Validation Measures

The Composite Score of Ecological Vulnerability follows established guidelines from recognized methods. These include the following:

• North Central Texas Council of Governments – Regional Ecosystem Framework
• North Carolina Division of Water Quality – Yadkin-PeeDee River Basin Priority Watershed Atlas
• Environmental Protection Agency - NEPAssist
• Federal Highway Administration – Eco-Logical Approach
• Illinois Department of Transportation – Bureau of Design and Environment Manuel
• U.S. Department of Transportation – National Environmental Policy Act Guidance

Staff has also validated the Ecological Vulnerability Score using feedback from professional planners, engineers, ecologists, and other industry experts. This feedback was gathered and incorporated during several Steering Committee Meetings in the summer of 2022.

Finally, the Ecological Vulnerability Score has been tested against its stated purpose and shown to return results consistent with this purpose: Identify review-triggering resources, identify resources relevant to ecological integrity of the region, and identify area potentially ecologically impacted by transportation projects.

The Composite Score of Ecological Vulnerability is intended to be used as a preliminary screening tool to indicate the combined potential for ecological loss and environmental review for a project in a given location. This map/data was created by the Champaign County Regional Planning Commission (CCRPC) for use “as-is” and as an aid in graphic representation only. The data is not verified by a Registered Professional Land Surveyor for the State of Illinois and is not intended to be used as such. CCRPC, its officials, and its employees do not accept any liability for any discrepancies, errors, or variances that may exist.