The Science

Stone Harbor Bird Sanctuary

THE PROBLEM:
In a salt marsh affected by tidal restrictions, such as a culvert sized too small (like ours) to allow the normal amount of sea water, ground water salinity (salt content) is lowered. Less of the marsh surface is flooded at high tide, and there is decreased sedimentation which may lead to a relative drop in the marsh surface elevation. This favors the growth of Phragmites, and decreases the amount of Spartina (typical salt marsh grasses) growing.

THE SOLUTION:
With the reintroduction of normal tidal flow, restoration of the ecosystem can happen and Phragmites should decline. We plan to replace the one existing 12” pipe with two new 24” pipes.

The current pipe is about 160 ft long and traverses under Third Avenue. Although the pipe is 15 inches at the bay, the interior diameter of the pipe extending into the sanctuary measures 12 inches. The pipe is improperly fused or joined. Two different materials were noted on video inspection. The recording device traveled a length of approximately 94 feet , noting a material change about 12 feet from the bird sanctuary and a second material change at 94 feet in from the bird sanctuary. The second material change also resulted in sag of greater than 50%. Debris has build up at the three separate pipe sections.
All this has lead to the decreased tidal exchange.

THE EFFECTS:
The height of Phragmites decreases with increased salinity. Phragmites will decrease in height and extent of cover after tidal flow is restored. The depth of the water level has an impact on the growth of Phragmites.
Other salt marsh plants, such as Spartina grasses, will reestablish themselves after a tidal flow is restored.
Birds and other animal species prefer Spartina grasses and other salt
marsh plants to Phragmites.
Fish are less abundant, smaller, and there are fewer species within a tidal
restriction than outside a tidal restriction.

Fish are an important food source for the wading birds as well as eating mosquito larvae. Helping to control the mosquito population

IF NO ACTION IS TAKEN:
Phragmites stands are still growing and will cover more
of the salt marsh in the future if no measures to restore
natural tidal circulation are taken. Phragmites stands harbor less biodiversity than the Spartina and cattail stands. Phragmites prefer to grow where there is lower salinity levels.
Spartina grasses grow where salinity is higher. Salinity is higher where tide is not restricted and lower within an area impacted by a tidal restriction.