LEARNING & EXPLORING

Cultural & Natural Resrources

The Study Committee was tasked with determining if there is at least one outstanding resource value (ORV) associated with the Eightmile River. Six outstanding resource values were identified for the Eightmile River Watershed. The analysis of these values (as described in detail in the Watershed Management Plan and briefly below) represents a thorough set of scientific and social research as well as an intentional and collaborative process by the Study Committee. The six outstandingly remarkable values found to make the Eightmile eligible for Wild and Scenic designation are: watershed hydrology, water quality, geology, unique species and natural communities, watershed ecosystem, and the cultural landscape.

NOTE: Each ORV briefing on this page includes a "More Details" link to a page containing detailed text from the Watershed Management Plan, downloadable posters and links on each topic. These detail pages will also grow as we learn more about the ORVs.

Watershed Hydrology	Unique Species and Natural Communities
Water Quality	Watershed Ecosystem
Geology	Cultural Landscape

 

Watershed Hydrology - More Details

Unlike many watersheds in Connecticut today the Eightmile River Watershed is not relied upon as a major source of public or industrial water supply, nor is it impacted by significant point source discharges from wastewater treatment plants or industrial sources. The watershed has a very low level of impervious surfaces (currently only 3%) which is a strong indicator of high quality hydrologic processes. In addition, the watershed has over 80% forest cover (compared to the entire state at 60%) and only 6% of the riparian corridor area within 100 feet of the 160 miles of rivers and streams has any development associated with it. These qualities put the Eightmile River in a unique position for sustaining an intact hydrologic system.

It is rare in Connecticut, especially along the coast, to have a watershed system of this size with a natural, intact flow regime in place throughout the system with indicators of that flow regime well below thresholds for degradation. As such the Eightmile River Watershed can be considered exemplary of how a natural hydrologic system in Connecticut functions.

Some key findings on the exemplary status of watershed hydrology in the Eightmile River Watershed: There are no water diversions with any recognizable impact to natural flow regimes. No dams currently regulate flow. Of the three remaining dams within the streams proposed for designation two have mitigation measures to allow fish migration and the third is slated for removal and restoration. Additionally, the small impoundments associated with these run-of-the-river dams are historic and scenic in nature and do not detract from the overall context of the river. No point source discharges exist from industrial sources or wastewater treatment nor are there any other known discharges. Very low levels of impervious cover exist throughout the watershed. Currently at 3%, these levels fall well below levels known to affect watershed hydrology. The ratio of forest land cover to developed area is very favorable for intact watershed hydrology with over 80% of the watershed forested.

 

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Water Quality - More Details

Robust biological indicators show water quality in the Eightmile Watershed to be very high with very few current sources of degradation. The data demonstrate that water quality and aquatic habitat in the Eightmile is not only locally exemplary, but as good as the best rivers studied in the state.

In addition to having outstanding water quality, major threats to water resources that are typically seen in other watersheds are almost nonexistent in the Eightmile. Currently, there are no point source discharges in the Eightmile watershed and indicators of non-point pollution such as impervious surface cover levels (at 3%) indicate that the watershed is currently significantly below degradation thresholds (ranging from 4-10%). Other key features that indicate high water quality include intact riparian corridor lands and a natural hydrologic system (as described above).

Some key findings on the status of water quality in the Eightmile River Watershed: 93% of the Eightmile’s rivers and streams and 99% of the groundwater meet the State of Connecticut’s highest water quality classification- Class A -or better. This classification has among its designated uses potential drinking water supply and fish and wildlife habitat. Most if not all of the remaining waters exhibit Class A characteristics but for technical reasons are not classified as such. Aquatic insect studies indicate that conditions within the watershed are among the very best in Connecticut. There are no wastewater or industrial surface point discharges in the watershed and there are no subsurface discharges impairing water quality. Forested land cover is high and impervious surface cover is low (see hydrology above). Riparian corridors are essentially intact and continuous (see hydrology above). A natural hydrology and flow regime exists for ground and surface water systems.

 

Geology - More Details

Many aspects of the geology in the Eightmile River Watershed stand out as being regionally and locally significant. In addition to ecologically significant and relatively rare non-acidic soil and bedrock areas, the unusual alignment of bedrock in the watershed creates a rectangular or “blocky” local topography that is unusual in Connecticut and the region as a whole.

The watershed’s geology plays a critical role in overall watershed quality affecting resources from hydrology to biodiversity to the cultural landscape. The combination of an exceptional assemblage of bedrock, atypical local topography and exemplary glacial evidence remains all provide a distinct representation of geology in Connecticut and as such is considered an outstanding resource value for the Eightmile River Watershed.

In 1966, Lundgren described the bedrock of the Eightmile River Watershed as “an exceptionally varied suite of rocks that includes representatives of nearly all of the major stratigraphic and granitic units known in eastern Connecticut”.

 

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Unique species and natural communities - More Details

Studies of rare species, biodiversity and ecological communities found the Eightmile River Watershed to be in the top tier of watershed basins in the New England region. Present in the watershed are over 150 plant and animal species of high conservation value and nearly 100 significant natural communities. Globally, nationally and state listed species were found, and the number of new significant species found within a relatively short period of field work indicate that there is still much to be discovered in the watershed.

When ranked among New England watershed basins in terms of number of rare species per unit basin area, the Eightmile watershed ranks in the 96th percentile in terms of rare species and in the 99th percentile in terms of globally rare species. During a relatively short field survey initiated by the Study Committee, 27 new occurrences or locations of State-listed rare plants were documented.

The quantity of “at-risk” plant and animal species known from the Eightmile River watershed is substantial. A summary of species considered to be ‘rare’, ‘threatened’, or ‘endangered’, in a state, regional, and/or global context, in addition to species that have been identified as ‘of special concern’ shows a total of 155 such species in the watershed. This list is comprised of 32 vascular plants, 6 amphibians, 81 bird species, 8 fish species, 12 invertebrate species, 7 reptiles and turtles, and 9 mammals.

Several qualities of the landscape contribute to the ecological diversity. One is the high percentage of forested habitat in the Eightmile River (80%). This is comparable in Connecticut only to watersheds in the northwest and southeast corners of the state which are recognized as having the highest known biodiversity in New England. Similarly, relative to the rest of Connecticut, a low percentage of the Eightmile River watershed is developed, there is a low density of roads (2.62 mi/mi2), and a high percentage of the watershed is occupied by large roadless blocks (72% occupied by roadless blocks greater than 1000 ac). All three parameters are strong indicators of a high level of habitat connectivity and intactness.

Though not the rarest species known to occur in the Eightmile watershed, the Cerulean Warbler is arguably the highest-profile wildlife management issue. The Eightmile watershed appears to have among the highest breeding-season densities of this bird in New England. It is perhaps the most area-sensitive of all North American birds, and is experiencing rapid range-wide decline. The Cerulean Warbler has been listed as a species of high global conservation concern by several international avian conservation organizations.

Overall, the combination of species and natural communities offer the rarity, abundance and diversity that support a biologically diverse Eightmile River watershed ecosystem. This combination is clearly unique and exemplary not only within Connecticut but throughout New England and as such qualifies as an outstanding resource value for the Eightmile River Watershed.

Some key findings on the status of unique species and natural communities in the Eightmile River Watershed: The total of known extant State-listed plant occurrences in the watershed is 54 occurrences. Eleven of these species are also New England regional rare species, and several of these occurrences are of regional significance. Approximately 100 occurrences of natural communities in the watershed were “significant” according to our research. Potentially the most important biodiversity features of the Eightmile River watershed are the extensive meta-occurrence of “warm-season” grasslands, which represent among other things an important reservoir of native genotypes of grass species. As raked among the 417 New England regional basins in terms of number of extant rare species per unit basin area, the Eightmile ranks in the 96th percentile in terms of extant total rare species, and in the 99th percentile in terms of extant globally rare species.

 

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Watershed ecosystem - More Details

The most outstanding of all characteristics of the Eightmile is the intact, high quality watershed ecosystem. The Eightmile River Watershed ecosystem reflects the sum of the many interacting ecological features found throughout the watershed. The fact that each of these features are generally in excellent condition means that their sum at the ecosystem level is synergistic – “greater than the sum of the parts” - and that an outstanding overall ecosystem is the result. Key components defining the structure, function and landscape context of the watershed were found to be favorable for designating the watershed ecosystem as an outstanding resource value.

Key components of the intact Eightmile watershed ecosystem are:

Structure

• Rare, diverse and abundant species and natural communities
• Extensive habitat which is intact and connected
• Limited presence of invasive species
• High water quality
• Stream connectivity throughout most of the watershed
• Natural channel morphology
• Extensive forest and vegetative cover

Function

• Hydrology of the watershed is as natural and unimpaired as any in Connecticut
• Sediment and scour characteristics are natural
• Nutrient and energy cycles reflect an undisturbed system
• Size of habitat and a low level of system manipulation allows natural disturbance regimes
• Context of the watershed within the southern Connecticut River Valley landscape is favorable.
• By definition, delineating the ecosystem at the full watershed level incorporates the full range of land-based ecological functions which occur within the system.

When combined with the specific qualities of each of the previously described natural resource ORVs (water quality, hydrology, geology, unique species and natural communities) these characteristics of structure and function easily qualify the watershed ecosystem as an outstanding resource value.

Some key findings on the status of the watershed ecosystem in the Eightmile River Watershed: The Eightmile watershed contains all of the critical components of a high quality watershed ecosystem and these components are in excellent condition. Many of these are characterized by the other ORVs. The quality of key ecological processes such as nutrient and energy cycling is excellent. Immediately outside of the Eightmile Watershed, the landscape remains largely intact providing a good buffer for the Eightmile system and greater overall ecological integrity. A large portion of the Eightmile watershed’s forested portion occurs as large, unfragmented blocks (e.g., 72% of the watershed consists of large connected roadless blocks of habitat 1000 acres or more). There are also other indicators of high habitat connectivity and intactness such as high percentage of forested area and small amounts of development. The Eightmile watershed has relatively low levels of invasive species. The absence of flood control structures allows streams within the watershed to host in abundance various riparian communities that are dependent upon periodic flooding and natural scouring.

 

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Cultural landscape - More Details

The rural character, history and intact bucolic landscape contribute to the significance of the cultural landscape for the Eightmile River Watershed. The watershed remains a rural place, with small settlements, winding roads and trails. There are no large commercial developments and the few convenience stores are outnumbered by general stores and farm stands. Small dispersed hamlets and farmsteads, as well as town greens and 18th and 19th century buildings, are connected by a road network dating originally to the Colonial era. The historic pattern of settlement and human circulation within the watershed still exists today.

Nearly 300 archaeological and historic architectural sites have been identified for the towns and villages of the Eightmile River watershed, 23 of these are located within ¼ mile of the Eightmile River main stem and the East Branch. The historic sites, nine of which are listed on the National Register of Historic Places, include buildings, bridges, mills, dams, cemeteries and wharfs as well as historic districts.

When compared to other watersheds of similar size in Connecticut all of these features combine to make the Eightmile River cultural landscape exemplary as an outstanding cultural resource value.

Some key findings on the status of cultural resources in the Eightmile River Watershed: The Eightmile River watershed landscape is a significant example of a successional agrarian landscape in southern New England that is relatively undisturbed by 20th century urbanization or other modern development. Lands bordering the Eightmile River have a high potential for intact archaeological resources. Many of the 17th, 18th and 19th century buildings, structures, and sites analyzed as cultural landscape study areas demonstrate the high degree of historic integrity that remains, particularly in architectural form. The topography, past land use, and lack of modern development contribute to a unique watershed landscape allowing for the possibility of many additional intact archaeological sites to exist.