Survey of the Green Harbor River


Marshfield, Massachusetts

December 2003

3rd draft

Laurie Bianchi, M.Ed

Whitman-Hanson Regional High School

600 Franklin Street

Whitman, MA 02382






Table of Contents









Historical Review






Specific Gravity




Dissolved Oxygen


Surface Water Level


Depth of River






Secchi Disk


Observation and Results


Biological Survey




Discussion and Recommendation




Appendix A


Appendix B


Appendix C


Appendix D


Appendix E


Appendix F




    The Green Harbor River in Marshfield, MA, has experienced many changes over the past two hundred years because of storms and human intervention. A dam and tide gates were built by farmers in 1872.  The dam affected the harbor by increasing shoaling and restricting boat access into the river from the ocean.  There was great opposition, particularly from the fishermen, and, although the Massachusetts legislature passed a bill to remove the dam and replace it with a bridge in 1898, the Governor vetoed the bill. The dike remains to this day. An 1898 report shows that the tides were still allowed in and out of the river on a daily basis. In the 1920s there is evidence of a fully functioning estuary with clams, quahogs, horseshoe crabs, and many other species. The ecosystem continued unimpaired until 1969 when new tide gates were installed that totally eliminated tidal induction into the river. Sluice boards were installed which kept water in the river so that the water would not drain into the harbor except when the water level was higher than the sluice boards. Water quality deteriorated rapidly. At times the tide gates have leaked over the years, allowing a limited number of species to exist. However, there are no remaining clams, quahogs, horseshoe crabs, or striped bass.  There was a herring run in the river, which essentially stopped once the tide gates were closed.  A survey of the river begun in the summer of 2003 examined the water quality and chemistry of the river.  Due to a leaking tide gate, ocean water has been entering the river sporadically during the survey.  The findings indicated that the river is cleaner when there is tidal induction and degraded when limited tide or no tide enters the river. The salinity levels showed that the river is brackish, particularly in the depths, though much less so after rain events. The water levels never reached mean ocean tide during the survey, although water -mark evidence indicates that over the years the water has reached higher levels.  The river is shallower than in the past, which contributes to higher water temperatures and lower dissolved oxygen levels. A brief biological sampling was conducted which showed that there are a number of species present in the river that are associated with estuaries. Some of the animals identified were mummichogs, eels, flounder, crabs, shrimp, periwinkles, etc.  More information should be collected to determine the full nature of the river system, particularly in the biological realm. More water level data needs to be taken so that the effects of tidal induction can be assessed. The town should consider allowing more tide to enter and exit the river to insure the survival of the estuary while maintaining a water level low enough to avoid property damage from flooding.




    The Green Harbor River has a rich and interesting history influenced by politics, economics, and local color. It is also a peaceful and beautiful waterway inhabited by a diversity of aquatic life, insects, and birds. Over the past two hundred years nature and man have altered the river and its water quality to such an extent that the river has ranged from productive estuary to stagnant pond.


    This survey was conducted in an effort to determine the water chemistry, water quality, and type of ecosystem upriver from the dike which limits tidal induction from the Green Harbor side of the river. In the most recent study Green Harbor River Flooding Impact Investigation completed in 1993 by the U.S. Army Corps of Engineers, some recommendations were made. A biological study and assessment of the water quality and environmental impacts were suggested. This preliminary survey was an attempt to answer some of the questions raised by the Corps study and provide baseline data about the river.


    The Green Harbor River upstream from the dike is a brackish body of water with an estuary community. The previous statement is based upon past knowledge of the river from the 1960s when during my childhood, the tide flowed freely into the river twice daily and mud flats were exposed at low tide. Since salt water is more dense than fresh water, even when tidal induction is limited or stopped, the salt water would remain at the bottom and not exit the river because of the sluice boards which restrict the amount of drainage. Though some mixing of layers would take place with wind and other turbulence, some salinity will always be present in the benthic zone.

Historical Review

    Long before Europeans set foot on the shores of New England, Native Americans made their homes in Marshfield. Belonging to the Algonquin family, these local natives relocated seasonally to take advantage of the many resources available. Evidence exists that a tribe lived on or near the historic Winslow site and "shell heaps of considerable size are found at Green Harbor" (Autobiography of a Pilgrim Town 3). In the spring the natives would relocate to the rivers where "salmon, shad, herring, eels, sturgeon, and other fish would be taken" (Autobiography 1).

     The first record of a white man working in this locale was the spring of 1623, when William Green started a small fishing station along the beach near the mouth of the river. There were fishing weirs set up in the river (Autobiography 3). It is believed that the river was named after William Green (Autobiography 21), and in the earliest records and maps the river is named Greene's Harbour River. 

    In 1632 Edward Winslow was granted 200 acres of land in Marshfield. This land was called Greens Harbor and abutted the river. His family took up residence on his "Green Harbor farm" in 1636 (Krussell 3-5). A General Court order in 1633 made travel easier between Plymouth and Green Harbor by permitting construction of a water passage to connect the Green Harbor River estuary and Duxbury Bay. In 1636 another court order required that the canal be eighteen feet wide and six feet deep (Autobiography 22). The channel was to make possible boat passage from Plymouth Harbor to Green Harbor River (Report of the Joint Board upon the Restoration of Green Harbor 6).

     "The fertile valley of the tidal Green Harbor River offered some of the richest farm lands to be found in Plymouth County" (Krussell 1). Farm land appears to be the factor which would eventually cause the change from a tidal river to a protected estuary. Salt hay was a valuable resource and general grazing was allowed in many areas around Green Harbor. However because of problems associated with cattle along the beach and salt marshes, in 1785 the Court was given a petition to end that practice. Though the Court did not create an act, the paperwork gives evidence of the location of salt marshes on the river: 

No act was granted at this time, but in connection with this petition a copy of a will was presented, in which the marsh lands in the vicinity of Bass Creek a tributary of the Green Harbor River, entering it about a mile above the dyke, are referred to as "salt marshes " (Joint Report of the Board 6). 

    The next record relating to the river was in 1806, when "proprietors petitioned the General Court for an Act of Incorporation permitting them to build a canal from Green Harbor to Duxbury Bay. It was enacted" (Autobiography 239). This Green Harbor Canal Company's purpose was to drain the marsh by making canals so that the water could travel to Duxbury Bay and Plymouth. This project would presumably make the farm land more productive and possibly provide more acreage (Autobiography 239). The present-day Cut River is the result of this canal dug behind the Green Harbor beach (Krusell 7). Ironically, "soon after this work was accomplished, a November storm completely closed the mouth of Green Harbor River, and for several years the only outlet of drainage for all the Green Harbor marshes was through the creek or canal to Duxbury Bay" (Autobiography 239). The date of this occurrence is stated as 1809 in "The Great Storms" (Krusell 5). The river turned into a degraded pond, and the marsh proprietors became distressed. Chapter 39 of the 1807 Acts and Resolves of the State gave the Green Harbor Canal Company, and the proprietors of the marshes as well as "associates, and their heirs and successors" to the marsh, the right to do work necessary "for the purpose of draining the stagnant water." Methods such as building canals, bridges, dikes, removing sand, "rocks, or other obstructions that oppose the draining of said marsh" were all possibilities (Report of the Joint Board 8).

    Originally, the mouth of the river was located "just south of Cut Island at the Duxbury line near Canal Street, Green Harbor" (Krusell 7). A new and current mouth of the Green Harbor River is approximately five eighths of a mile north of the old mouth (Report of the Joint Board 7) and was opened by another storm in 1810. It was "further cut through by forty local fishermen, under cover of night, to widen the entrance for their boats. The outlet between Bluefish Rock and Green Harbor beach is known as the Narrows" (Krusell 7). Though some sources differ on this account attributing the new mouth entirely to fishermen, a petition dated in 1812 supports the storm forcing a new mouth rather than only the fishermen. It also speaks to the nature of the salt marshes and the problems arising from stagnation: 

The petition to the Green's Harbour Canal Company in the County of Plymouth - Humbly shews, - that the said Company are Proprietors of a certain Tract of salt Marsh-land, lying in the town of Marshfield in said County of Plymouth - that said Marsh is defended from the Sea, on the Northeast, by a Beach called Marshfield Beach - that Anno Domini 1806 the River called Green's Harbour River, which runs thro' said Marsh and Beach into the Sea, was filled up with Sand, by a violent Storm which caused the whole Marsh, together with the low Land contiguous thereto, to become a Lake, by estimation, of about 2000 acres of stagnant Water - that, on this emergence your Petitioners were obliged to open a Canal into Duxbury Bay and build a bridge over the same; which cost them nearly 2000 Dollars - - the Canal answered a good Purpose for draining the Marsh; but did not admit sea water enough into the Marsh to preserve it, in its former State; some Parts thereof producing Rank Weeds of various kinds, and other Parts Nothing at all- Anno Domini 1811, another violent Storm forced a new Channel or River thro' said Beach, at a considerable distance from where the former River was filled up, and said Channel now remains, sufficient it is said, at full Tide, for a Vessel of 100 Tons to enter. 

(Report of the Joint Board upon the Restoration of Green Harbor 8-9) 

    Further documentation of the state of the river can be found in literature surrounding Green Harbor's most famous resident, Daniel Webster. Referring to some time before 1827 when Webster bought his house, Laurence Bradford writes how Webster was impressed by "the scenery which had a sort of wild, uncultivated look, partially wooded, with an undulatory surface of small heights which afforded picturesque views of the sea and the extensive reaches of marshes" (Bradford 110). By this time, the soil had been depleted, and Webster made mention of this fact in a speech at Rochester (Harvey 271). Webster, an avid outdoorsman, hunter, and fisherman, loved his farm, the river, and the ocean. He had a boat house along the river and fished often while in Marshfield (Harvey 279). Webster mentioned the menhaden, a species of herring, that appeared off Marshfield in June or July. They were caught with seine nets and taken by the cartload to the farm in an effort to enrich the soil. Ten to twelve loads per acre were used, attesting to the abundance of these fish (Harvey 273). They were not valued for eating, being too oily. The estuary and salt marshes must have been very large at that time, according to Webster's letter to Mr. Blatchford dated December 7, 1847: 

The moon changes to-day, the tides are high, and, at eleven o'clock, the sea will cover all the meadows, and reach the wall of our garden. P.S. I went down to the mouth of the river at high water. The marshes are all covered, there was not a breath of wind but the sea looked cold and blue (Curtis 314). 

    A guest to Webster's home confirms the observation: "On going to my window, I saw Mr. Webster, towards the ocean, standing on the point of the bay which stretches inland to his garden wall" (Lyman 137). Since his garden was two miles from the ocean, the extent of the tidal influence in the river at that time was much larger than it is today. 

    A ferry was running across the river by 1869. Another major change to the river took place when the dike was constructed: "Before the dike was built in 1872, the river was brackish as far inland as Webster St. West and inland of the Webster St. underpass the river was fresh water" (Krusell 7). An act of 1871 "For the improvement of Green Harbor Marsh and other purposes" granted the proprietors permission to build. An important part of the act stated that "should shoaling take place above the level of mean low water in the channel in consequence of dike construction, it was to be removed by the Marsh proprietors." This clause and the resulting shoaling within four years caused the "Harbor and Land Commissioners to demand its removal." Fishermen were affected by the shallower channel because they were not able to gain access to the harbor at all tides as in the past (Autobiography 239-240). Schooners could no longer access the harbor and river to deliver wood to a lumber yard. The dike was the demise of the lumber yard. A feud between the fishermen and the proprietors began and lasted for a number of years. The dike was widened in 1879 so a road could be built on it (Joint Report 14). Some fishermen tried unsuccessfully to destroy the tide gates with explosives around 1894 (Autobiography 241). 

    The feud was still going strong, and in 1896 a study was commissioned to be completed by the Harbor and Land Commissioners and the State Board of Health to investigate removing both the dam and dike. The act stated: 

If substantial improvement in and benefit to Green Harbor will result from the removal of said dam and dike, and that no damage to vested property rights greater than the benefit and improvement to be derived from such removal will result therefrom, then the board of harbor and land commissioners shall remove said dam and dike, and shall replace such portion of the highway as may be destroyed by such removal, by a suitable bridge (Joint Report 3). 

    However, the board voted not to recommend the removal of the dike even though they stated: 

It is undoubtedly true that the small harbor has deteriorated since the building of the dike and we believe that the dike is responsible for a portion of the mischief done; but, as will be seen by the brief statement of the history of this river, it is not clear that the harbor has been at any time safe from a calamity similar to that which befell it in the earlier years of the century (Joint Report 14). 

    Key issues included whether the harbor would really be improved and what property damage might be incurred by the action. An interesting comment in the report is:

If the dike should be made tight, an amount of tide water at least equal to the present leakage through the dam might be allowed to flow up through the sluices in the dam during each high tide, and be discharged again into the harbor just before low water, in connection with the discharge of the surface drainage. This could not create conditions any more objectionable than those due to the present leakage; but serious damage might be done by the admission of too great a quantity of sea water, unless care was taken in the operation of the gates (Joint Report 58). 

    The details of leakage can be found on pages 36-37. The statements on leakage show that sea water was entering the river, that sluices were used, and that they could be regulated. Although the original intent may have been to keep the sea water out, the actual account was different: "It appears to be the practice to leave these sluice - gates partially open at all times and to raise or lower them only at infrequent intervals, whenever it is desired to raise or lower the water in the river above the dike." Apparently there were still tides in the river: "The bed of the main river is below the level of low tide for a distance of two miles above the dike, where there is a small bar which rises about one foot above low tide" (Joint Report 38). 

    The salinity in the river was also measured in this report. Twenty-six years after the dike was built, the surface water in times of large fresh-water flow (April and December) was generally 1.7-2.9 parts per thousand. In August the surface salinity ranged from 4.5 and 7 parts per thousand. 

Chemical examinations of the water in the creeks have shown that at all seasons of the year the water in the bottom of the main river and larger creeks, where the depth is such that the bottom is below low water, or but little above it, is composed largely of sea water. (Joint Report 24). 

    The amount was stated as 70% sea water. (Joint Report 39-40) If the dike were removed, large mud flats would be reestablished, which would cause odors similar to that on the opposite side of Dike Road in the harbor (Joint Report 24). 

    The largest damage to the dike was caused by a storm on November 26-27, 1898, when a "fifty foot wide breach" occurred (Krusell 50). Finally, in response to public sentiment, in 1898 "a bill was passed by the Massachusetts legislature to provide for the removal of the dike legally" (Autobiography 242). Though passing both Senate and House, the bill was vetoed by Governor Wolcott a few days later "since there was a clause in the measure providing that no money should be paid meadow owners for damages resulting should salt water again overflow their lands" (Autobiography 242). The dike had been so close to being removed that people actually marched and celebrated, but an error of omission sealed the bill's fate and that of the fishermen of Green Harbor (Autobiography 242). 

    Around the turn of the century, the literature makes little or no mention about the river, although opinions from disgruntled fishermen can be heard to this day. One 1900 reference to Burial Hill about two miles upstream describes "a wide expanse of salt marsh" to the North (Bradford 115). This description shows that even in 1900 the salt marsh was extensive. 

    Much of the later history of the river was obtained through interviews with local land owners, fishermen, and a trapper. During the Depression, the Dexter family resided along the river and harvested clams and quahogs from the river upstream from the dike. William Dexter hunted and fished the river and subsisted off the land. In the 1950s his sons Nathaniel and Daniel spent summers with their parents on the river. Nathaniel remembers sea otters, clams, quahogs, razor clams, winter flounder, striped bass, herring, smelt, white perch, crabs, horseshoe crabs, and alewife. Sally Doyle and Howard Annis dug quahogs and sold them by the bushel at the town fish market in the late 1940s. Edna Howland, past owner of the island in the river, remembers crabs, flounder, striped bass, white perch, eels, horseshoe crabs, turtles, barnacles, and clams living upstream of the dike, which was quite salty. Her father owned the island before her, it having past through the generations since the late 1800s According to Howland the water depth by the island was ten to twelve feet deep and generally clean. There were definite tides with mud flats exposed during low tide from at least the 1930s until 1969.  A fifty -pound striped bass was caught in the 1930s. Others recollect the above- mentioned estuary life and sea worms, shrimp, striped bass, white perch, periwinkles, snails (some an inch or more in diameter), and hermit crabs. Muskrat holes were abundant all up and down the river, and, with the amount of shellfish, otters were seen from time to time. Though the water level in the river was lower than in the harbor, the tide still entered the river in force twice per day and the tidal range was around two to three feet. Youths jumped off the cement walkway of the dike, and the braver souls even jumped from the road into the incoming tide. The water was quite deep in front of the dike at that time (Affidavits -see appendix). 

    Over the years the activities along the river changed. There were farms in operation along Wharf Creek and the Green Harbor River, but, according to one source in 1940, aside from some cranberry bogs, the dike marshes were "little used and seldom cultivated" (Autobiography 242). In 1931 a record states that the "Green Harbor jetties, which had been built in 1899, were reconstructed and dredging of the river was undertaken to keep the Narrows open for boats" (Krussell 59). This may have been the first record of dredging in the harbor. In 1956 at town meeting, plans were put into action with a Master Plan for the improvement of the Green Harbor tidal basin. The town pier, built in 1958, was a direct result of that plan. (Krussell 65). The Green Harbor Marina came into existence later and use of the harbor increased.

    In 1965 the U.S. Army Corps of Engineers did a study entitled "Detailed project report for Small Navigation Project, Green Harbor, Marshfield, Massachusetts." Circa 1969 new tide gates were installed, and the tidal flow was stopped. Reasons for this change in management have not been confirmed at this time of publication. The gates were apparently made differently than the previous tide gates, or perhaps, the old gates were  in such a state of disrepair that huge tidal flows had entered the river for at least fifty years.  As a result of the new tide gates, high tide did not enter the river for some years. In addition, the new sluice boards trapped water behind the dike and prevented a low tide from occurring. When the water level in the river became higher than the top of the boards (on outgoing tide), water would flow out into the harbor but at other times there was no exchange of water with the ocean. Without the influx of clean salt water and with limited fresh water flowing downstream in the summer, the water quality seriously deteriorated and many people did not bother to use the river for recreational purposes anymore. According to Krusell in her 1990 book Marshfield: A Town of Villages, on the harbor side of the river the "number of fish caught has diminished and the clam flats so rich with succulent soft-shell clams in the 1940's, are now contaminated and have had to be closed" (Krusell 66). 

    When Mass. Audubon acquired Dwyer's Farm in 1984, there was more interest in the river and water quality. Some biological surveys were done along their property, whose eastern end is located approximately one mile upstream from the ocean. At that location, in recent years the surface salinity has been low, rarely rising above 7 parts per thousand. The species of fish netted May 10, 2003 were pumpkinseed, banded killifish, mummichog, golden shiner, white perch, inland silverside, and American eel. 

    Eric Blauss, co-owner of the island in the river, has been concerned for many years about the water quality and its effect on the life in the river. His island journal documents some of the environmental changes in the river. After 1969, when new tide gates were installed, the river took on a brownish color and was not suitable for swimming: "The water was no longer capable of supporting marine life. The river was dead and nobody cared except for us" (Blauss 55). By the 1980s, siltation had occurred in the river and its tributaries, causing it to be more shallow and muddy. Warren Dwyer never really noticed the rise and fall of tides while working his farm; however, years after the tide gates prevented the tides from entering the river, the mud got worse and his cows would occasionally get stuck. Some were pulled out, but some were so mired in the muck that they died there. David Smith, local resident, helped in some rescue efforts. Others confirm that the water quality deteriorated, and people stopped using the river for recreational purposes. Fishing is perhaps the most widespread recreational use that ended in the 1970s. While people used to fish for striped bass, flounder, and white perch in the river side, that practice ended when the tide gates closed. Feelings still run strong regarding the management of the Green Harbor River. In a newspaper article entitled "Environmental benefits of opening tidal dike," both Dave Clapp, Director of South Shore Sanctuaries of Mass Audubon, and Eric Blauss are quoted as favoring a restoration of the tidal flow. Blauss "said he thinks at least one of the gates could be opened without flooding. As a rambunctious high school youth, he said, he consistently jammed the gate open so that water could pass through, and nobody noticed." According to Clapp, "It would be quite thrilling, I think, to actually have some of these back meadows at an elevation where they could be covered with salt water on a regular basis, making huge mud flats for migratory birds to use." On the other hand. Clapp also believes that "it would be difficult to restrain the water unless there was a major project to move the dike upstream. According to Jim O'Connell, a geologist for the Massachusetts Coastal Zone Management agency (MCZM)," (Mednick. 1) 

Opening the dike might improve water quality, reestablish a historic fish run, rid the river of abundant elephant grass and possibly even abate shoaling at the mouth of the river." "Currently, O'Connell said, salt water is seeping through some broken boards at the dike, which has four gates. If that much water does not contribute to flooding, then it might be possible to allow some tidal water to enter the river, he said. (Mednick. 1)

     Audubon ecologist Elizabeth Colburn found salt water one mile upstream and water level three feet below mean sea level. She said, "If the door were opened, the water level would rise and possibly flood septic systems in residential areas; but if the doors were repaired and shut tight, that could make the river more difficult to flush and cause plant growth, which would kill fish" (Mednick. 1). 

    As a result of a request from MCZM, the U.S. Army Corps of Engineers performed a six month reconnaissance study (low-level inspection intended to find general information.) to investigate the potential for flooding if the tide gates were opened (MacLellan 1). Although the study concludes "that opening any tide gates at the Dike Road Bridge for the purpose of restoring tidal flows to the Green Harbor Marsh could increase flooding of properties adjacent to the Green harbor River," a number of interesting points emerged from the report. Since it was expected that the tide gates could be closed during coastal storms (and thus remove that concern), only rainfall events were considered along with normal tidal flows. The authors pointed out that the "bridge structure will still impose a significant restriction to tidal flow" even if the gates were opened (Corps 7). With all four tide gates fully open and sluice boards removed Table Five shows that, at maximum spring tide with average annual runoff, the water level would go from 2.1 ft at high tide in the marsh to 1.5 ft at low tide (ft NGVD) for a range of .6 feet. With one gate open, the level ranged from 1.3 ft at high to 1.1 ft at low, a difference in water level of .2 feet. Table Four shows the tidal routings with all four tide gates open and sluice boards removed in large rainfall events. The 100 -year runoff, in a worst -case scenario, yields a high tide in the marsh of 3.6 ft and a low of .6 ft for a range of 2.6 ft. In comparison to the average annual runoff, the data is .9 ft at high and .2 ft for low with a range of .7 ft (Corps Tables 4-5). The report does not "evaluate the environmental impacts and benefits of restoring tidal flows to the Green Harbor River" (Corps 2). It also makes no mention of allowing partial flow of tide into the river. However, it is stated that

 The tidegates presently restrict tidal flows into the Green harbor River and it is possible that changing the current mode of operation of the tidegates could restore the salt water marsh and reestablish a historic fish run, as well as increase the tidal prism with possible benefits on a decreased shoaling rate of the harbor entrance channel (Corps 1). 

    Options presented include a larger opening at the bridge which would allow for a greater tidal range and "lower minimum water level" in the river. A self-regulating system was also suggested that could prevent flooding by closing at a certain level (Corps 24). 

    At the time of the study, there had been salt water infiltrating the river for several years, and the river had cleaned up somewhat. According to Jim O'Connell of MCZM, "The steel, swinging flood gates are in a state of disrepair, and two of them are partially open, allowing an as yet undisclosed amount of sea water into the estuary. In a letter to the Corps, O' Connell was uncertain of the benefits or pitfalls of any repairs or management changes, stressing that the town has the ultimate responsibility for determining new policy" (MacLellan 1). There were crabs, flounder, seaworms, and periwinkles re-established in the river, and clams had seeded themselves in the mud. In 1994 the tide gates were once again replaced, and tidal flow was restricted from the river. Thousands of seaworms crawled out of the mud and expired, according to Blauss. Since then, there are times when tide enters the river for months at a time and times when no water flows in. When the water level is low, no water flows out, either. The water remains stationary and stagnates.




Current Research



Eco-explorer rubber boat with see-through panel in bottom and oars

16 foot canoe, paddles, life vests and cushions

5 gallon white pails

plankton net

secchi disk

water collection device

seine net

dip net (fine mesh)

crab net


SeaTest specific gravity meter

100 mL plastic graduated cylinder

LaMotte dissolved oxygen test kit

pH test kit for salt water and fresh water

Nitrate/nitrate test strips



Sediment sampling device

data sheet

pen, pencil, colored pencil



meter stick

metric ruler

sounding line with lead weight

assorted white and clear containers for biological specimen

small plastic fish tank (1 Liter)


magnifying boxes and hand lense

field guides


minnow traps



1. Visit the river on a weekly basis (one day per week).

2. Perform investigations during both low and high tide cycles on the river side. Note the water level.

3. Do water quality testing first during each visit. Testing must be done every trip.

4. Check the specific gravity and the pH from both the surface and depth of one meter.

5. Conduct a biological survey to note the diversity of species living in and on the river.

6. Use any of the following: dip nets, seine net, minnow traps, and plankton net for capture.

7. Sketch and/or take photographs of fish and other animals when time allows.

Procedures for the specific tests are described separately below and in the appendix.

Specific gravity

Rinse collection bottle or water collection device with water sample. Collect water sample. Rinse plastic 100 mL graduated cylinder with small amount of sample. Empty and then fill with 90 mL of the sample. Place hydrometer gently in the graduated cylinder. Read from bottom of the meniscus. The hydrometer was manufactured by Marine Enterprises International, Inc., Baltimore, MD.


Using the specific gravity data and the conversion chart in the appendix, determine the salinity. The accuracy for the conversion chart was checked late in the season with a Sea Test Full Range Specific Gravity Meter by Aquarium Systems. It agreed with the conversion chart from specific gravity. Protocol: Pour sample to line. Tap sides to release any air bubbles. Read the salinity in parts per thousand (ppt) from pointer. Next years study will add this to the protocol.

Dissolved Oxygen

See appendix A for LaMotte dissolved oxygen test kit protocol. Fixed the sample at the site and finished the test at home. Titration method.

Surface Water Level

There is a board attached to the cement of the dike walls on the river side. It is marked with feet above and below mean sea level. The board was viewed from the rocks on the north side of river at river level. During autumn and winter it was viewed from the street level.  From the North side of the dike, lean out slightly against the metal railing and the board can be read.  See photo below.  Note that there are positive and negative levels.  0 is mean sea level.  The bottom of the board is -2 ft.

Water level data (work in progress)


Depth of river

Attach sounding line to weight. Lower until the line goes slack. Record depth in meters by markings on line.


Rinse testing container with sample. Empty. Place sample water in up to the line. Add four drops of indicator if using the Freshwater High Range pH Test Kit, three drops if using Freshwater pH Test Kit. Replace cap and tip gently several times to mix. Compare to color chart. Used test kits for salt water aquaria and/or fresh water depending upon results of the specific gravity test. Ranges were 7.2-7.8 for High Range and 6.0-7.6 for Freshwater Kit. Kits made by Aquarium Pharmaceuticals, Inc.


Quantofix test strips were used. Pour a few drops of sample onto test strip pads. Wait thirty seconds for color to develop. Compare to color chart on side of test strip container.

Secchi disk - Water Transparency

Attach secchi disk to the marked line. Lower over the side of the boat until it disappears from sight. Lift slowly until just visible. This shows the depth to which light can penetrate and is an indicator of the turbidity of the water.

NOTE: See pictures of collection devices and equipment in the appendix.

Globe protocol and further information- click below

Observations and results

Data Time Last Tide Water Level (ft) Air Temp (F) Water Temp (surface/1 meter) (F) Salinity (surface/1 meter) (ppt) Secchi Disk (m) Diss. O2 (ppm) Surface pH  pH 1 m
7/10/03 11-1 AM High 8:38 AM -2 74 60/60 30.5/NA 1.75 9.1 8.4 8.4
7/17/03 10:25-1 Low 8:38 AM -2 77 74/68 19.4/27 1.25 7.1 7.8 8.2
7/25/03 10:35-1 High 9:17 PM -1.5 82 61/60 5.55/16.7 .75 6.6 7.2 7.6
7/29/03 10-12:50 Low 6:06 AM -1.5 75 72/64 22/27 1.5 7.6 7.6 7.8
8/8/03 11-1:15 High 8:25 AM  -.5 80 73/66 8.3/15 .5 5.5 7.2 7.4
8/15/03 9:50-12:45 Low 8:08 AM -2.5 80 75/70 5.55/19.43 .2 3.2 7.0 7.2
8/22/03 8:30-1:45 High 7:43 AM < -1 76 74/NA 5.55/27.76 .2 4 7.2 7.4
9/1/03 2:15-3:40 High 3:09 AM -2 71 64/62 30/32.5 1 NA 8.2 8.2
9/7/03 2:25-3:00 Low 1:59 PM -1.5  72 68/NA 24.5/NA 1.2 NA 8.0 NA
10/11/03 10:45-12:45 Low 6:27 AM -2 63 56/NA 30/NA 1.5 NA 8.2 NA

Individual data charts and sketches are available by clicking on the corresponding date.  


More water level data


Biological survey

List of species observed


Banded killifish,         Fundulus diaphanus

Mummichogs         Fundulus heteroclitus

Inland Silverside         Menidia beryllina

Tautog         Tautoga onitis

Winter Flounder (juveniles)         Pleuronectes americanus

American eels         Anguilla rostrata

Two other species not positively identified; one a Stickleback sp.


Periwinkles         Littorina littorea

Mussel (juvenile)         Mytilus edulis

Empty mussel shells (hundreds of them by dike) probably died out around 1970 when new tide gates were installed.


Green crabs         Carcinus maenas

Grass shrimp         Palaemonetes sp.

Another species of shrimp

Amphipods (Corophiid and Gammarid)

Northern Rock Barnacles         Semibalanus balanoides



Sea Worm; Nereid



Copepods (Calanus sp)

Crab zoea and mysis-zoea


Barnacle cyprid and molts


Amphipod Corophiid

Amphipod Gammarid


Diatoms; Navicula

Cladospherans; Daphnia



Dragon fly


Damselfly larva in water

Horse fly

Water boatman

Some type of surface tension skimmer (see preserved speciman)



Tiny flies


Great blue heron


Double crested cormorant

Herring Gull




Red winged blackbird



Enteromorpha sp.

Tube weed

Cladophora (not a positive ID yet) Algal bloom that forms thick greenish/brown floating mats in the river.

Sea lettuce Ulva (came in with tide - not growing on river side)

Fucus (came in with tide - not growing on river side)

Golden algae


    This survey was undertaken with the intent of discovering the biodiversity of the ecosystem, water chemistry, and water quality of Green Harbor River. One day per week a visit of approximately three hours was made to the river, and water testing was done with regard to specific gravity, pH, temperature, dissolved oxygen, clarity (turbidity), depth, current water level, nitrate, nitrite, and odor. Biological samples were captured by dip net, seine net, and minnow traps. 

    Results from this survey and a literature review show that water quality in the Green Harbor River has been variable in the near and distant past. During the first visit on July 10 the water was very clear and clean, and there was an influx of water at high tide. The bottom of the river was visible from every location tested, including the channel. Crabs were visible scurrying around the gravel bottom in front of the dike. The dissolved oxygen content was high at 9.1 parts per million (ppm), which is healthy for the ecosystem. Salinity ranged throughout the summer from 5.5 - 30.5 parts per thousand (ppt) at the surface and 15- 27 ppt at a depth of one meter. The surface salinity varied with rainfall events and the amount of tidal water entering the river. Not surprisingly, salinity was higher when the visits were on a high -tide cycle and lower on a low- tide cycle. The collection process was not ideal, since the container started filling immediately on immersion so that the salinities at depths are most likely higher than the data shows. The upper layers of water, which were less brackish, entered the tube and mixed with the lower water. There appears to be a salt water wedge in the river. In the 1898 study of the river, the channel was found to be 70% ocean water after twenty-six years of the dike's existence. The more recent restriction of tidal flow began about 1969. Therefore both this and the 1898 report are consistent in that there is brackish water found in the depths of the river. The more saline depths also explains why two healthy juvenile flounder were caught at a point midway on the south side of the island in one meter deep water. 

    The water quality declined as the summer progressed. In late July, algal mats had grown to large proportions and filled about half the waterway on the north side of the island, and there were also mats on the edges of the river on the south side of the island. By mid-August the water was turbid and low in oxygen. Water at high -tide cycle leaked in slowly and in small amounts. The lowest dissolved oxygen reading was 3.1 ppm, which is extremely poor. The water temperature had risen to 72 degrees F, which had a negative impact on the dissolved oxygen (less oxygen can exist in warm water than in cold water). Another variable in the water temperature is the depth of the water. From soundings taken on a day with surface water level at -2 feet, the deepest location in the channel near the dike was 2 meters. The rest of the channel varied around 1.5 meters. This river is more shallow than in the 1960s; therefore, water temperatures increase more readily, which causes lower dissolved oxygen readings. The water appeared opaque and brownish-red, and the secchi disk disappeared in .2 meters. Although the river has a history of this coloration, this sample was the most turbid and occurred after a large rainfall event. Little ocean water was entering during the higher -water levels. There was little chance of any photosynthesis adding oxygen to the water during the last weeks of August. One could not see fish under the water, though some would jump at the surface for the abundant insect life. 

    There appears to be a correlation between tidal induction and water quality. When more ocean water entered the river, the water was clearer and had a higher dissolved oxygen content than when little tide entered the river. This data was contrary to a supposition made in the Flooding Impact study that more tide entering would cause a deterioration in water quality. This hypothesis was based on two inferences by the U.S. Army Corps of Engineers, which apparently were not backed up by any data. The Corps assumed that the river above the dike was a freshwater body; therefore, the biology would change if the tide gates were opened: "Presently, the upstream pool from the sluice boards is assumed to be essentially a freshwater pond" (Corps 9). However, there is no apparent evidence to support the assertion that the river was freshwater near the dike and much more evidence to support the contention that the river was brackish, at least in the depths of the river. After the Flooding Impact was distributed, the tide gates were replaced, according to the Marshfield DPW, and once again no tide entered the river. Soon after there was a major die off of thousands of seaworms. Since nereids need salt or brackish water to survive and time to reach maturity, the river must have been brackish for at least several years. Research and personal experience with the river support the view that the river was an estuary at least until the early 1970s and probably functioned marginally after that time depending on the leakage from the tide gates. There must have been either a major exodus on low -tide cycle of those species which could escape or some severe population drops with those that were trapped behind the dike. Three very large dead striped bass were observed floating by a trapper in the 1970s. 

    This body of water appears to be a marginally functioning estuary with a range of fresh to brackish water, as well as a salt water community in front of the dike. Biodiversity appears to be limited, which is not surprising considering the stressed conditions of the river. Many factors have affected the organisms which have lived in the river. Most dramatic would be the abrupt cessation of tidal flow in 1969, which lasted for some years and still remains a problem for the water quality. The influx of salt water had previously flushed out the river, thereby keeping the water much cleaner and cooler in temperature. The outgoing tide also swept silt and other materials out into the ocean, scouring the bottom and keeping the channel deeper on both the river side and the harbor side. The placement of sluice boards on the river side prevented this drainage from taking place and may have increased the average height of the surface water though more data collection on water levels will be necessary. The river has become more shallow over the years because of these changes. Materials deposit in the river instead of going out to sea. The channel depth has changed from an estimated twelve to fifteen feet in 1970 to a maximum of six to eight feet today (depending upon the surface water level). The shallow depth has a negative impact on the temperature and dissolved oxygen levels. The effects of the relatively quick deposition (a loss of 4-6 feet in thirty-five years) could be devastating in the long term. Succession can take place much more rapidly and over time the river will become more narrow and more shallow, which will cause still warmer temperatures, less dissolved oxygen, more plant growth, and eutrophication. Organisms in the river will be under even more stress than in years past. The sluice boards are a major variable in this depth issue. Although they keep the water level up in the river and prevent an appreciable low tide from occurring, they also prevent the scouring effect caused when water rushes out during a low-tide cycle. A daily low-tide would help prevent the massive siltation occurring presently. As inferred by previous researchers, allowing a low-tide could also help prevent the deposition in the harbor which has occurred more extensively since the 1970s. Dredging records should be studied to gain insight on the relationship, if any, between the tidal river (pre-1970s) and the non-tidal river (post 1970). Also it must be noted that a sewer pipe is located under the dike and water actually flows under and over the pipe. As stated in the U.S. Army Corps report of 1993, this pipe is a restriction to flow and could be affected by the pressure of fast tidal outflows.  

     In the summer months, even with large rainfall events of five inches and more, the mean water level never reached 0 ft. on visits. There was no sign from rocks or cement that the level had reached 0 during these months. The range in water level was between -2.5 ft to -.5 ft. In the spring the water levels must occasionally reach above mean sea level, as evidenced by old water marks on the cement. An attempt was made to visit on or about spring tide and after major rainfall events to estimate the maximum summer water level. The level would appear to be around -.5 ft, a reading taken after a major rainfall (5 inches) and at the highest level for the tide cycle. There does not appear to be a significant difference in surface water level between low and high tide in the river, possibly a range of .2 - .6 ft. However, visits were only three hours in duration, so this estimated range is merely an inference based on observations. More data on water levels at high tide, low tide, over the course of a single day, spring tides, neap tides, coastal storms, rainfall, and other related events would be useful. If the water level gets too high, more water could be drained from the river by removing more sluice boards during a low -tide cycle. Similarly, in the event of a predicted major storm, water could also be drained before the storm. The drainage possibilities are probably underutilized, and sluice boards might actually increase the flooding during large rainfall events.

     The tide has come in for a majority of the last 133 years, allowing the estuary characteristics to remain. As a result of testimonials and personal knowledge of the river, this author infers that a very healthy estuary existed from about 1900 until around 1969, until new tide gates were installed which totally restricted incoming tide. After that time, inflow of tide has been sporadic, and the community has changed accordingly. Herring used to come up the river in the spring and still do according to some fishermen. The fish try to jump up the waterfall on the outgoing tide from the river. Stripers follow them into the harbor. Herring have been netted at the dike in recent years, so apparently there is still a possibility of restoring the run. The possibility that any large adult estuary fish like flounder, eel, white perch, and striped bass still enter or live on the river side is unlikely, but juveniles of all these species except striped bass have been found in the river this year. Plankton samples showed a variety of marine and some fresh water organisms. Samples were found to be sparse in August, attesting to the poor water quality. Healthy plankton is essential to the food web.

     By the end of the summer, one could discern that any organisms in this river would have to be well adapted to the environmental changes subjected to their ancestors over the centuries. Some species that were supposed to prefer the freshwater end of estuaries were captured in areas of high salinity. In an effort to determine the extent of their tolerance to low oxygen and salinity, three grass shrimp, four banded killifish, three mummichogs, and two inland silversides were placed in a small plastic aquarium (about two liters in volume) with river water. They were left in the container with an input of air but no filter for eight days. They were fed twice daily. One silverside died after two days. All the rest survived the cramped quarters and low oxygen and were put into a school salt water aquarium on August 27. The tank had a specific gravity of 1.022 (salinity of about 30 ppt ) on that date. The water came from the coast at Brant Rock and was pure ocean water. One banded killifish died two days later. The rest were still living as of December first. Although mummichogs are notoriously tough and well-adapted, the banded killifish and inland silverside are doing extremely well in conditions which one might expect to be detrimental to their health. (Note:  The other silverside died over Christmas vacation and two killifish disappeared over April vacation, 2004).

Discussion and Recommendations 

     More biological sampling is required to determine the extent of the estuary community in the river. It may be concentrated in front of the dike or could also be farther up the river. Benthic sampling needs to be done in many locations. Line transects could be done in order to sample the plant life along the river. Phragmites, an invasive plant, have extended their range greatly since the 1960s. Mapping and measures to control this spread could be undertaken. 

    A bathymetric survey could be done to show the water depth in comparison to the surrounding land elevations. Sedimentation over the years is a factor in most rivers. As rivers get shallower, temperatures rise, dissolved oxygen declines, and water quality becomes worse. Populations undergo stress. A baseline of this data would give a basis for comparison in the future. The dimensions (e.g. width) of the river should be measured to observe if the river gets smaller over time. 

    An archeological dig could be done at some time when the river gets extremely low. Although low -tide cycle is incomplete at present, there have been some summers when the water level was extremely low, and mud flats were exposed due to low rainfall and groundwater levels. A dig could confirm which species existed in the river from the early 1900s through 1970. 

    That estuaries are among the most productive ecosystems on earth is a scientific fact. They are necessary nurseries for many species of fish and invertebrates and are critical to the ocean food web. Even a single estuary affected by pollution or improper management is a loss to humanity. As the EPA and US Army Corps of Engineers are looking into the revitalization of estuaries across the US, perhaps Marshfield should consider the value to the community of regulating tidal flow more efficiently, allowing more salt water in and out of the river. One should also consider that a greater outflow may prevent the shoaling taking place in the harbor. If less dredging were necessary, a large cost savings could result.

 Although  the tide gates (standard flap gates) are designed to prevent water from entering the river, some experiments and restoration projects have involved chaining the gates open to allow various tide scenarios  (Reiner 1).  The town should consider how best to ensure the survival of the estuary while maintaining a water level low enough to avoid property damage from flooding. Since the US Army Corps of Engineers notes no likely problems except in twenty-five -year and one-hundred-year floods, one can predict the possibilities of allowing more tide to enter the river daily and also allowing more to exit. With vastly improved meteorological forecasts, more sluice boards could be removed prior to a storm to allow an actual low tide to occur before the storm. Then there would be less opportunity for flooding than with the current setup. Another important note is that there are no septic systems to flood as there is  now town sewerage.

    This report was based on a preliminary survey, and conditions can change rapidly in an ecosystem. Sampling and more extensive study should continue if one is to determine the complete nature of Green Harbor River.



Blauss, Eric. "The Island." Unpublished memoirs of the Green Harbor River and island. 2000.

Bradford, Laurence. Historic Duxbury in Plymouth County Massachusetts. The Fish Printing Company, Boston, 1900.

Curtis, George Ticknor. Life of Daniel Webster Volume II. D. Appleton and Company, New York, 1870.

Davis, Charles. The Marine and Fresh Water Plankton. Michigan State University Press, 1955.

Harbor and Land Commissioners and the State Board of Health, Report of the Joint Board upon the Restoration of Green Harbor. Wright and Potter Printing Co, Boston, MA 1898.  Click here for a printable version.  Must have Acrobat reader.

Hartel, Karsten, David Halliwell Alan Launer, Inland Fishes of Massachusetts. Mass. Audubon Society, Lincoln, MA, 2002.

Harvey, Peter. Reminiscences and Anecdotes of Daniel Webster. Little, Brown and Company, Boston, 1877.

Krusell, Cynthia and Betty Bates, Marshfield A Town of Villages 1640-1990. Historical Research Associates, Marshfield Hills, MA, 1990.

Krusell, Cynthia. "The Great Storms and How they Altered Our Shores." Marshfield Mariner, 2/16/1978.

Lyman, General S.P. The Public and Private Life of Daniel Webster Volume II. U.S. Book Company, New York, 1852.

MacLellan, Andrew. "Dispelling rumors Engineers Study effects of Green Harbor Flooding." Marshfield Mariner, Vol. XXI No. 29, 10/2/1992.

Mah, Wendell and Charles Wener, Green Harbor River Flooding Impact Investigation. U.S. Army Corps of Engineers, Waltham, MA, 1993.

Marshfield Tercentenary Committee, Marshfield 70-40'W: 42-5' N The Autobiography of a Pilgrim Town. Rapid Service Press Inc, 1940.

Mednick, Amy. "Environmental Benefits of Opening Tidal Dike." Boston Globe South, 1992

Migdalski, Edward and George Fichter, The Fresh and Salt Water Fishes of the World. Greenwich House NY, 1976.

Reiner, Edward.  Assorted e-mails. Environmental Protection Agency.  Boston,  2004.

Smith, Deboyd, A Guide to Marine Coastal Plankton and Marine Invertebrate Larvae. Kendall/Hunt Publishing Co., Dubuque, Iowa, 1977.

Teal, John and Mildred. Life and Death of the Salt Marsh. Little, Brown and Company, Boston, 1969.

Weiss, Howard, et al, Maine Animals of Southern New England and New York. State Geological and Natural History Survey of Connecticut, Department of Environmental Protection, 1995.

Zim, Herbert and Jurst Shoemaker, Fishes A Guide to Fresh and Salt-Water Species. Golden Press, NY, 1991.

Internet Sources

U.S. Army Corps of Engineers. Accessed 7/15/03

Affidavits and interviews.

 Annis,   Blauss, Donald,  Blauss, Eric,   Blauss, Wesley,  Dexter, Doyle, Friedrich,  Gilson, Howland, Tobin.                        

Affidavits are available in Appendix B or online by clicking on the name.  Papers without signatures are on the internet for security reasons.  Originals may be viewed by contacting Laurie Bianchi.

Related sites of interest

Appendix A

Data sheets and sketches.  Click on individual dates in data chart to view.

Photographs and diagrams of water level board, area of plankton tow, secchi disk, turbidity tube, and sounding line

Dissolved oxygen protocol

Salinity chart from specific gravity

Turbidity tube protocol (used in October and will be used next year)

Pictures of collection devices and equipment

Pictures of Green Harbor River

Appendix B

Affidavits - See above for listing

Appendix C

Fish Day at Daniel Webster Wildlife Sanctuary : MA Audubon flyer

Data from Fish Day 5/10/03

Gulf of Maine Marsh-Estuarine Fish Species

Assorted keys and identification of plankton and fish

Appendix D

Boston Harbor Educator's Conference: MA Bays Estuary Program

Selected Resources for Coastal Studies

Ecological role of Estuaries

So What Can I Do to Help Protect Our Coastal Bays?

What is Anadromy?

Estuarine Habitats

Estuaries: Gateways to the Ocean

Appendix E

Assorted copies from U.S. Army Corps of Engineers web site and Green Harbor River Flooding Impact Investigation     Click here

Entire text (printable version) of  Harbor and Land Commissioners and the State Board of Health, Report of the Joint Board upon the Restoration of Green Harbor

Appendix F


Photographs of the river- Powerpoint

Web pages created by Laurie Bianchi and Claire Peterson, WHRHS.  This is only the third draft and links are not yet complete.  Please be patient as information will be added as time allows.

Any corrections or comments may be directed to

Anyone interested in helping out in any way can e-mail

December 23, 2003

Click here to view 2004 Report