In West Haven, the invasive species phragmites has taken over the swamps and rivers. This species crowds out other plants in the area and is unsuitable for wetland’s wildlife, which creates a monoculture. This species is not aggressive and cannot compete with other plants in an environment in which there is too much salt due to the fact that salt aids the salt grass, the natural plant of the area. The phragmites was able to overcome the salt grasses because of tide gates place in the rivers in order to control the flow of water. These tide gates caused the drying out of the rivers and prevented flooding. This declined the salinity in the area and flow of salt water which produced and inefficient environment for the salt grasses. Eventually the phragmites spread down the swamps and along the rivers, evicting the salt grass. The dense roots of phragmites prevented the absorption of salt water during floods by the soil, preventing the regrowth of salt grass. Along with the fact that phragmites makes environments inhabitable for wetland species, they also are a fire hazard and spread fire readily.
The herbicides imazapyr and mysophate are used in combination to kill phragmites and mulch growing was used to break down plants so more plants could grow. These methods are employed by a machine called the marshmaster which is used to pull out phragmites. This machine sprays out herbicides from the side and has track at the bottom to help it move in the flooded marsh. Also, it is able to travel across water in order to reach different parts of the swamp. The machine is made of aluminum and is washed thoroughly in order to prevent rusting. After a second treatment, the salt grasses have started returning to the river bank and floods carry seeds into the marsh. The wildlife has slowly been returning to the area. An anaerobic sulfur reducing bacteria decomposing detritus layer lies under the marsh as a root layer for new organisms. Flooding the marsh brings in salt and sulfur to break down this layer.
There are three salt marshes in West Haven: Oyster River, Cove River, and Old Field Creek. In order to aid marsh restoration, tide gates are used. In the Oyster River there is unrestricted tidal flow and it is treated and mulched, but there has not been much success. In the Cove River “slab tide gates are used but do not work efficiently so human intervention is also necessary. In Old Field Creek, self-regulating tidegates(SRT) are used. Even though Old Field Creek was the least replenished, the SRT’s helped the creek rebuild itself.
A tide gate can be engineered to allow the flow of water in and out of a marsh while being efficient for each of the salt marshes located in West Haven. This design will be alike to the self-regulating tide-gate, which worked the best compared to the other methods used in the other marshes. In the research project, different tide gates will be evaluated so that the most effective design, material, and structure can be used for the West Haven marsh’s tide gates.
1. Using different resources, study the structure and design of different tide gates.
2. Find the most effective and inexpensive tide gate design and materials to propose for the West Haven marshes.
3. Make small adjustments to the proposed tide gate which will increase its ability to allow the flow of nutrients while controlling tide flow.
4. Download a designing program which allows engineering of the proposed and adjusted tide gate.
5. Design the tide gate with modifications to show the adjustments.
Proposed and Modified SRTG:
In conclusion, a self-regulated tide gate should be used for the West Haven salt marshes. In previous efforts, the marshes using ‘slab’ tide gates and lack of treatment showed no improvement, but the Old Creek River was able to recover quickly due to the use of a SRT. This proves that the hypothesis was correct. The use of a self-regulating tide gate would be most useful in replenishing the marshes with salt water for the salt grass and aid the eradication of phragmites.
The modifications made on the current SRT would allow the adjustable float to hang at the bottom of a metal arm connected to the tide gate. When the tides are overflowing the float would move upwards with the tide, causing the gate to lower over the opening in the gate. This would prevent overflow in the marsh. When the tides lower the float would lower with it, raising the gate to allow the flow of salt water, wildlife, and nutrients into the marsh. This design allows the ultimate control of the tides without constant human interference.
For further research, the self-regulating tide gate proposed in this project could be built and tested in an actual salt. Or a way could be found to test the design engineered in this project. The SRT that was designed could be tested in order to prove that it would function more efficiently than tide gates currently in use and other methods used to replenish the salt marshes of West Haven. If this tide gate worked more efficiently, then it would replace the methods used in the Cove River, Old Creek Field, and Oyster River.
In addition, for further research different materials could be used to build the new tide gate to see which would be the least expensive while also the more able to uphold the SRTs structure. This would make is so SRTs would be more affordable for towns so that they could replenish their salt marshes while not completely expending the budget available. Due to the exposure to water, these materials could not be easily eroded, nor should they present any immediate dangers to the wildlife in the bodies of water. Also, the materials would have to be able to suspend the structure of the SRT, so they must have high surface tension.
The objective of this project is to design a successful tide gate for the West Haven marshes which can control the flow of water and allow the flow of wildlife and nutrients.
IV: The SRT modified to have the adjustable float attached to an arm connected to the gate, controlling the movements
DV: How efficiently the tide gate is on the marsh
Hypothesis: If an SRT is used on the West Haven marshes, then the salt will be allowed to flow in, replenishing the salt grasses and aiding the eradication of the invasive phragmites plant.
West Haven Cove River
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