Management Area - Land Cover Analysis

The intent of the Section 6217 management area delineation is to ensure adequate protection of the state's coastal waters.  The geographic scope of the coastal nonpoint source pollution control program must be sufficient to ensure implementation of management measures to restore and protect coastal waters. 

The existing coastal zone boundary does not afford the level of protection necessary to control sources of nonpoint pollution that, individually or cumulatively, significantly impact the state's coastal waters.  A very small percentage of the state's coastal drainage area is encompassed by the existing coastal area/coastal boundary, which was established as a zone of direct influence on coastal resources rather than secondary, cumulative, or indirect impacts.

However, based on the following analysis, the management area originally proposed by NOAA is, based upon scientific information, excessive for purposes of controlling nonpoint sources of pollution in Connecticut.  A Section 6217 management area which encompasses substantial portions of the northwestern and northeastern sections of the state may result in ineffective program administration, requiring implementation of management measures in areas of the state where land uses do not, individually or cumulatively, impact coastal waters.

Therefore, Connecticut proposes to include in its Section 6217 management area additional land areas beyond the coastal boundary that have a significant, measurable impact on coastal waters, thereby ensuring more effective management of relevant land and water uses.  Based on evaluation and agreements of the Long Island Sound Study, a participant in the National Estuary Program, and best available scientific understanding of the Long Island Sound watershed and pollutant delivery system, the proposed management zone will afford a level of protection in excess of Section 6217 requirements, while remaining politically achievable, credible, and enforceable.

In deciding the necessary extent of the management zone, the DEP considered three critical factors:  1) land uses likely to contribute pollutants of concern to Long Island Sound based on land cover; 2) proximity to the Sound of those contributing land uses; and 3) existing condition of coastal waters, including both areas of impaired uses and those that might be threatened by future development or other pollutant-contributing land uses.  

Land Cover

The relationship between certain land covers (and land use activities) and pollutant delivery is not controversial, although export co-efficients vary widely depending on local conditions.  The literature documents the correlation between increased pollutant loads and increased human activity (Donigian, et al., 1990; U.S. EPA, 1982; Frink, 1991; NYSDEC, 1992; Omernik, 1976; McCreary et al., 1992).  For most pollutants, natural land cover exports the lowest load, and urbanized land cover, the highest.  Agriculture is a third broad category generally referred to, and it generally exports pollutant loads higher than natural land covers but lower than urban land covers.  There is considerable overlap of export rate or co-efficient ranges among the three categories and not all pollutants rank in that order, but the general relationship holds true for most settings. 

This relationship is largely attributable to the percent of impervious cover associated with each land cover category.  Natural covers have few impervious surfaces while imperviousness increases with level of development.  More impervious surface promotes increased runoff and decreased pollutant capture from activities that occur on impervious surfaces or from deposition on the impervious surfaces.  Furthermore, both agriculture and development impact the availability of natural vegetation that would normally buffer runoff and pollutant delivery to surface and ground waters.

The LISS has characterized this relationship between land use and pollutant delivery in the development of its Comprehensive Conservation and Management Plan (CCMP), which received final approval on September 12, 1994 by the Governors of Connecticut and New York and EPA Administrator Browner.  For example, nitrogen has been identified by the LISS as the pollutant most responsible for causing extensive hypoxic areas in Long Island Sound during late summer.  According to the LISS, urban land cover delivery of nitrogen per unit area is at least three times as high, and may exceed five times as high, as what runs off of forested lands.  Agricultural runoff provides approximately twice as much nitrogen as forests per unit area and may exceed three times as much.  Many other pollutants have a similar relationship to urbanization because of the increased level of impervious cover in urban environments.

Using a Geographic Information System (GIS) land use/land cover database generated by researchers at the University of Connecticut (Civco et al., 1992), urban land percentage in each town in Connecticut was calculated.  Urban land is liberally defined to include seven land cover categories: impervious surfaces, high density residential and commercial, medium density residential, roof, pavement, turf and grass (which captures large lawn areas of low-density neighborhoods), and major roads.  The LISS has defined more than 20% urban land cover as a critical break point for nonpoint source management need.  There are 64 of Connecticut's 169 towns with more than 20% urban land cover (Figure 1).  Forty-four towns have more than 30% urban land cover (Figure 2).

Figure 1: Connecticut Towns with >20 Percent Urban Land Cover

Figure 2: Connecticut Towns with >30 Percent Urban Land Cover

Clearly, towns with the highest percentage of urban land cover are concentrated along the southwestern coastal area, in the Quinnipiac River basin, and along the upper Connecticut River in the Hartford-Springfield, MA corridor.  Smaller urban areas include the Danbury area and the New London-Groton area on the Thames River.  These areas were identified for additional investigation in developing the management area for the Section 6217 program.

Proximity to Long Island Sound

Monitoring and modeling programs and studies show that pollutant loads discharged or run off into riverine systems are subject to loss or attenuation during transport (Donigian et al, 1990; Howarth et al., 1991; Phillips, 1991).  This is especially true for non-conservative pollutants (e.g., BOD, nitrogen, bacteria), which are subject to biological or chemical conversion, but also holds true for more conservative pollutants.  Conservative pollutants may become buried in sediments, deposited on floodplains during high flows, or be taken up into plant or animal tissues.  Also, the form of a pollutant may change, rendering it biologically unavailable, as, for example, when available ionic forms of metals bind with sulfur, inorganic sediments, or organic matter (DiToro et al., 1990).  While these substances are not truly "lost" from the system, many of the sinks effectively retain the pollutants to the extent that they can be considered permanent, and are generally not transported to coastal waters.

The LISS has demonstrated the attenuation of nitrogen during transport along the major tributaries that discharge to Long Island Sound (Frink et al., 1993; LISS, 1994).  For example, the Connecticut River contributes nearly 14 million kg of total nitrogen to the Sound each year (HydroQual, Inc., 1991).  The "natural" component of that load; that, is the amount of nitrogen that the river is believed to have discharged under precolonial conditions, is approximately 12.7 million kg per year.  By difference, the anthropogenic load of nitrogen contributed to Long Island Sound from sources in the entire Connecticut River Basin is approximately 1.3 million kg each year.  Of the documented human sources of nitrogen inputs throughout the basin, 7.8 million kg of nitrogen per year are identified (this amount is likely to be underestimated since point source contributions were estimated throughout the basin and nonpoint sources could be reasonably approximated only in Connecticut).  This means that only about 16% of the nitrogen contributed by sources in the Connecticut River actually makes it to Long Island Sound.  The attenuation loss estimated for the Connecticut River is similar to the 17% export efficiency of nitrogen calculated by Jaworski  (1992) for the Upper Potomac River Basin.  Interestingly, Jaworski et al. also reported an even lower export efficiency for the conservative pollutant, phosphorus, of only 8%.  Clearly, conservative pollutants can end up in long-term storage by burial, sorption, or biological uptake.

In smaller basins, less attenuation of pollutants is likely to occur because transport times are less.  The Quinnipiac River, for example, discharges 415 thousand kg of nitrogen per year past the Wallingford gage, the lowest, non-tidal monitoring station on the river.  The natural load would be about 134 thousand kg per year, leaving 281 thousand kg per year as the human contribution.  An estimated 463 thousand kg of nitrogen per year are contributed from sewage treatment plants and nonpoint runoff above the Wallingford gage for a 40% attenuation during transport.  Additional attenuation will occur between the Wallingford gage and Long Island Sound, as well.  The basin size-attenuation rate was briefly discussed by Howarth et al. (1991) in relation to sediment transport.  Sediment delivery ratios decrease as drainage area increases, suggesting an increased opportunity for sediment storage as basin size increases.  The nitrogen attenuation in the Connecticut River versus the Quinnipiac River seems to support those estimates.

In a similar data investigation of the Quinebaug River Watershed, a 37 percent attenuation rate between the monitoring stations at Quinebaug and Jewett City occurred for phosphorous and a 12 percent attenuation rate occurred for nitrogen.  These rates of attenuation are consistent with Long Island Sound Study information and support the proposed management area decision for those towns on the Thames/Quinebaug River System.

Using these relationships between transport and attenuation, the LISS has concluded that the most concentrated nonpoint contributions of nitrogen to Long Island Sound originate from a very small land area adjacent to the Sound.  Excluding New York City (because of uncertain drainage patterns) and the atmospheric deposition of nitrogen directly on the Sound's surface, the 13% of the total land area closest to the Sound in New York and Connecticut contributes more than 40% of the anthropogenic nonpoint nitrogen.  In the Connecticut tributary basins, the 10% of the land closest to the Sound contributes more than 30% of the anthropogenic nonpoint nitrogen.

Also supporting the attenuation argument for both nitrogen and bacteria is the Water Quality Standards Policy No. 21 for surface waters.  This policy states that domestic sewage treatment plants south of Interstate 95 need to continuously disinfect  all treated domestic sewage discharges year round to protect the sanitary quality of shellfish resources.  Yet, north of Interstate 95, this disinfection policy is required only from May 1 to October 1, recognizing the need to protect the sanitary quality of bathing waters.  Essentially this long-standing policy supports the attenuation argument for nitrogen and pathogens, recognizing that direct coastal impacts are derived from land uses in near proximity to those waters.

The proposed Section 6217 management area includes 80 municipalities representing about 62% of Connecticut's urban land use, which is a high pollutant contributor in the state, while these towns represent approximately 42% of the state's total land area.  This means that management activity within the proposed management area is much more efficient in terms of reducing pollutant delivery to Long Island Sound than in more distant areas, both because of the concentration of pollutant-contributing land use and because of its proximity to Long Island Sound.  In addition, urban areas not included in the Section 6217 management area should have considerable opportunity for pollutant attenuation before reaching and during transport through the Section 6217 management area.  This reasoning is strengthened by monitoring data in the Connecticut River that show  attainment of designated use goals in the lower part of the river that are not supported immediately below the urbanized greater Springfield and Hartford area.

Existing Water Quality

The final criterion for selecting the proposed Section 6217 management area is existing water quality in need of either management or protection.  The LISS has identified nitrogen and pathogen control as the two most pressing water quality problems in need of management.  Both of those problems involve non-conservative pollutants for which management should focus on the near-coastal areas of most relevance.  For toxic substances, pollutants that are contributed by nonpoint runoff, the LISS did not identify additional management needs beyond existing point source and stormwater programs (LISS, 1994).

The focus on geographic areas and nitrogen/pathogen control is consistent with urban management approaches published by the EPA for nonpoint source management (U.S. EPA, 1990).  As stated in the forward of that publication, "In order for urban jurisdictions to focus limited financial and technical resources in an effective and efficient manner they must be able to relate identified or suspected water quality problems to source areas in an integrated approach."  In concordance with a similar philosophy of sensible, cost-efficient, and effective management, the LISS chose to focus management activity in areas that most directly affect Long Island Sound.  This same philosophy justifies a practical Section 6217 management area, as proposed herein, that will have a significant, beneficial impact on water quality of Long Island Sound.  Upon evaluation of this approach through monitoring, and as supported in the Section 6217 approval guidance (NOAA and U.S. EPA, 1993), a process for identifying requirements for additional management measures would be instituted, which might include expansion of geographic areas where additional measures could be justified.

In Connecticut's 1994 Section 305(b) water quality report, use impairments are related either to point source problems or to local nonpoint source problems, such as failing septic systems in coastal areas, recreational vessel discharges, or urban runoff surrounding local harbors and embayments.  In no cases are sources from distant, inland areas documented as causing use impairments in coastal waters.  The 1994 Section 305(b) report also has identified hypoxia and nutrient runoff and pathogens as primary coastal water quality problems in need of management (CTDEP, 1993).  To address those problems, the DEP is already implementing commitments of the LISS CCMP, which do not call for priority actions beyond a near coastal management zone that is considerably smaller than the proposed Section 6217 management area.

Section 309 Analysis

Based on the above land cover/proximity/water quality criteria, the majority of the state's southwestern urban centers are included in the highest priority sub-basins identified by the LISS, and as such have been identified as having the greatest potential to contribute nonpoint source pollution to Long Island Sound.  The LISS did not include the sub-basins in southeastern Connecticut within this highest priority area.  Although proximal to Long Island Sound, the southeastern-most sub-basins were excluded based primarily on the fact that the percentages of existing urban and agricultural land cover (uses) were not as significant in the southeastern sub-basins as in the western watershed sub-basins of the Sound.

Connecticut's Section 309 coastal boundary analysis found that there is significant potential for future development within southeastern Connecticut, as well as significant coastal resource and water quality values in southeastern Connecticut which should be protected from existing and future nonpoint source pollution.  These land use trends and water quality data have guided the delineation of Connecticut's Section 6217 nonpoint source pollution management area, clearly suggesting the incorporation of the relatively undeveloped southeastern portion of the state in addition to the heavily urbanized metropolitan areas adjacent to Long Island Sound to focus Section 6217 implementation on localized nonpoint source-related impacts from existing urban land uses and future development.

Accordingly, Connecticut's Section 6217 coastal nonpoint source pollution management area will encompass the municipalities comprising the first and second priority sub-basins identified by the LISS and Section 309 Boundary Assessment project in order to control the sources of nonpoint pollution that, individually or cumulatively, may significantly impact the state's coastal waters.  Based on the technical analysis conducted for the LISS and the Section 309 coastal boundary assessment, a Section 6217 coastal nonpoint source management area which incorporates the municipalities comprising the priority sub-basins extends inland to the extent necessary to adequately control nonpoint sources of pollution.

Connecticut's Section 309 coastal boundary analysis identified a substantial amount of urban land cover in the upper reaches of the Connecticut River.  However, these urbanized areas in the upper reaches of the river were not assigned a high priority by the LISS for pollutant management based on their distance from Long Island Sound and the river's attenuation of nitrogen and bacteria.  In fact, the coastal waters of the lower Connecticut River at Haddam/East Haddam are currently meeting their water quality goals, in spite of the presence of highly urbanized areas along the upper river.

In light of the substantial urban land cover in the upper reaches of the river, especially in the Hartford metropolitan area, the municipalities located immediately adjacent to the Connecticut River will also be included in the management area as a precaution to further ensure against nonpoint source pollution impacts to coastal waters and provide for additional resource protection.  While Connecticut is confident that the high priority sub-basins in the lower portion of the state would be a sufficient management area and adequately protect against coastal water quality impacts, the inclusion of the municipalities located contiguous to the Connecticut River in the Section 6217 management area will provide an additional buffer to coastal waters in the river and accommodate areas of urban development and population.

Further, the inclusion of the municipalities contiguous to the Connecticut River will allow for nonpoint source management of the river's floodplain, as well as uninterrupted management of the entire river as an integrated ecosystem, focusing coastal management-related issues such as flood management and the protection of other resources such as fisheries, wildlife, and freshwater tidal wetlands throughout the Connecticut River corridor.  Incorporation of the Connecticut River into the state's Section 6217 management area will also correspond to OLISP's regulatory authority in the Connecticut River for coastal, tidal, and navigable waters pursuant to the Structures, Dredging, and Fill statutes.

Therefore, Connecticut's Section 6217 coastal nonpoint source pollution management area will be comprised of the following municipalities (1990 populations included in parentheses; bold-faced type denotes an existing coastal municipality):

Ansonia (18,403), Beacon Falls (5,083), Bethany (4,608), Branford (27,603), Bridgeport (141,686), Cheshire (25,684), Chester (3,417), Clinton (12,767), Cromwell (12,286), Darien (18,196), Deep River (4,332), Derby (12,199), Durham (5,732), East Haddam (6,676), East Hampton (10,428), East Hartford (50,452), East Haven (26,144), East Lyme (15,340), Easton (6,303), East Windsor (10,081), Enfield (45,532), Essex (5,904), Fairfield (53,418), Glastonbury (27,901), Greenwich (58,441), Groton (45,144), Guilford (19,848), Haddam (6,769), Hamden (52,434), Hartford (139,739), Killingworth (4,814),  Ledyard (14,913), Lyme (1,949), Madison (15,485), Meriden (59,479), Middlefield (3,925), Middletown (42,762), Milford (49,938), Monroe (16,896), Montville (16,673), Naugatuck (30,625), New Canaan (17,864), New Haven (130,474), New London (28,540), North Branford (12,996), North Haven (22,247), North Stonington (4,884), Norwalk (78,331), Norwich (37,391), Old Lyme (6,535), Old Saybrook (9,552), Orange (12,830), Oxford (8,685), Portland (8,418), Preston (5,006), Prospect (7,775), Redding (7,927), Ridgefield (20,919), Rocky Hill (16,554), Salem (3,310), Seymour (14,288), Shelton (35,418), South Windsor (22,090), Stamford (108,056), Stonington (16,919), Stratford (49,389), Suffield (11,427),  Trumbull (32,016), Wallingford (40,822), Waterford (17,930), Westbrook (5,414), West Haven (54,021), Weston (8,648), Westport (24,410), Wethersfield (25,651), Wilton (15,989), Windsor (27,817),  Windsor Locks (12,358), and Woodbridge (7,924).

Conclusion

According to Section 6217 program development guidance, a state's management area must extend inland to the extent necessary to control sources of nonpoint pollution that, individually or cumulatively, significantly impact coastal waters.  The data provided above demonstrate that, from a land cover and proximity perspective, urban land uses in Connecticut contribute substantially more runoff than forested land and are more proximate to coastal waters than agricultural uses; in some cases, urban land uses are immediately adjacent to Long Island Sound and its major tributaries.  From a water quality perspective, most of the water use impairments in Long Island Sound and its tributaries are attributed to point sources or localized nonpoint source impacts, not more distant, inland sources. 

It is unlikely that land use activities beyond Connecticut’s Section 6217 management area will exert significant water quality impacts on Connecticut's coastal waters because of the distribution of urban development, the attenuation capacities of rivers, and the improvements in best management practices and development planning already in widespread use throughout the state.

Literature Cited