Natural Resource Inventory and Assessment - Town of Guilford

evaluation of current designated areas of septic systems in Guilford. In developed areas, lakes, which are
surface expressions of ground water, are also susceptible to contamination. Swimming at Lake Quonnipaug
is periodically closed due to unacceptably high bacterial levels.
Sources of stress: faulty septic systems, landscape fertilizers, pesticides, herbicides, leachate from waste
sites and contaminated wastewater discharge sites (See Map C-4), oil spills, road salt, heavy metals from
motor vehicles, household chemicals, hormones and pharmaceuticals, atmospheric deposition from car
exhaust and coal-fired power plants.
Altered sedimentation: Sediments are the primary contaminant found in stormwater runoff,
particularly in watersheds where development occurs on steep slopes. Construction activities can double
the pre-construction sediment loss of a site. Eroded soils transported to rivers are deposited on stream
bottoms, reducing habitat diversity (e.g., pools and riffles) and eliminating spawning areas and shelter used
by aquatic life. Suspended sediment also injures and clogs gills of fish and sensitive invertebrates.
According to the Marina Commission, excess silt in the West River is creating the need for more frequent
dredging of Guilford Harbor. In lakes and ponds murky water reduces light penetration and can kill
aquatic plants, interfere with feeding of vision-dependent fishes, and smother fish eggs.
Sources of stress: stormwater runoff from development and associated construction, road sanding,
removal of riparian vegetation
Loss of habitat: Freshwater systems are embedded within, and greatly influenced by, surrounding
uplands. (See Section D.) Many animal species, particularly amphibians and some reptiles, require these
uplands to complete their life cycles. Habitat loss therefore encompasses clearing or alteration of nearby
uplands, as well as outright removal or alteration of aquatic and wetland systems themselves.
Sources of stress: incompatible development
Altered hydrology (water movement and storage): The hydrologic regime is the primary driver of river
systems. As impervious surface increases or vegetation is eliminated, the amount of water that infiltrates
into the soil decreases, and stormwater moves through a watershed and into a freshwater body more rapidly.
This increased surface flow, coupled with traditional methods of stormwater management, result in altered
timing, duration, frequency, and magnitude of flood flows in rivers. The increased volume of water results
in unstable banks, channel widening, and channel bed lowering, promoting further flooding. Many
engineered structures are created to retain and delay delivery in order to mitigate flood impacts. This can
lead to the reduction of peak flows, water fluctuations, and periodic over-bank flooding, all necessary to
maintain instream and riparian health.
Sources of stress: incompatible development, excessive ground water withdrawal
Habitat fragmentation is the breaking up of a connected landscape into progressively smaller and more
isolated areas. Fragmentation within a river system, between wetlands, or between freshwater systems and
their uplands creates barriers to many species that must move within or among habitat types to complete
their life cycles, such as migratory fish, turtles, and salamanders.
Sources of stress: incompatible development, dams, incompatibly designed road-stream crossings,
increased traffic volume, bank stabilization materials and rip-rap, road curbing in areas with frequent
amphibian and reptile crossings
Invasive/non-native species directly replace native species through predation, competition, or other
means, and become dominant, reducing species diversity and the health of the system as a whole. These
effects vary significantly based on the invading species, the extent of the invasion, and the vulnerability of
the system being invaded. Invasive plants in Guilford’s freshwater systems include Phragmites, purple
loosestrife, Eurasian water-milfoil, and other plants can choke wetlands and shallow lake waters, interfering
with recreational use and sometimes causing oxygen depletion when the plants die and decompose. Bass
and other introduced sport fish have greatly altered fish communities. The highly invasive, quick-spreading
zebra mussel recently appeared in Connecticut waters and threatens to alter the state’s aquatic systems.
Sources of stress: release of organisms for sport (e.g, tadpoles, game fish), release of bait fish, release of
aquarium fish, horticultural introduction of non-native plants, boats (via attached plant seeds and larvae)
Natural Resource Inventory and Assessment Town of Guilford, CT C7
Freshwater