The Marindin Project
Being able to assess how the coastline is eroding and at what rate is of imminent importance because it can better inform coastal management decisions like dictating where people should and shouldn’t be building their homes. It is also of forefront concern for the NPS to understand how erosion will affect the National Seashore’s facilities since it can take an unpredictable and expensive toll.
The Marindin Project, a project undertaken by the Provincetown Center for Coastal Studies in conjunction with the National Seashore is doing just this by conducting a comparative erosion study to resurvey data taken 120 years ago by a surveyor named Henry Marindin. The results that come out of this project will assist in being able to better project long-term coastal change and help facilitate comprehensive planning.
For the first time, coastal position and form will be analyzed for spatial trends over time. The outcome will be the best quantified data of erosion processes to date and will provide rule-of-thumb guidelines for seashore managers to make decisions about coastal access, recreational uses and facilities planning for the decades to come.[i]
Demonstration of the system Marindin used to cast a lead line, gathering ocean depths.
This summer, working for the National Seashore I had the opportunity to participate in the Marindin Project, assisting Mark Adams, the GIS specialist for the National Seashore and Graham Giese. This involved helping chart what will be a complete coastal contour from Provincetown to Chatham as compared to Marindin’s historical data. The original data was the result of a survey conducted by The U.S. Coast and Geodetic Survey between 1887 and 1889 headed by Marindin to assess the rate of erosion that was taking place along the coastline[ii]. 229 total transects, otherwise known as ‘profiles’ were marked out along the length of the ocean side of the Cape with transects at regular intervals about 300 meters apart, collecting a beach profile from the bluff to a fifteen yard depth offshore.
Mark Adams and two Marindin Project volunteers preparing to go out and collect data.
Being able to provide a comparative analysis of exactly how the coastline has changed over this time period is momentous because “no previous studies have had access to the same series of historical snapshots of coastal forms (coastal profiles from 1887-9, 1964 and 2003).”[iii] Giese explains the significance of why they are resurveying these profiles:
It is important for us to resurvey these lines so that we can determine the change between that time and this…The results tell us how much material moved from one place to another over the 100+ years that have elapsed. By measuring the changes over the entire coastal system, we will calculate how much material moved from one place to another.[iv]
Surveying
The techniques we have access to today to be able to capture these coastal contours are radically more sophisticated technologically but differ little in accuracy. Henry Marindin, with the aid of a handful of assistants used traditional surveying methods to survey the coastal elevations and then used a rowboat to row out along each profile, dropping a lead line every several feet to be able to measure the ocean depth. Today with GIS technology, these transects can be measured much more expediently; using LIDAR imaging for the portion of each transect that occurs on land and bathymetry to measure ocean depth. Bathymetry is the study of underwater depth and using sounding equipment, a seafloor relief can be generated and recorded. LIDAR, which stands for Light Detection and Ranging is a type of remote sensing that uses an aircraft to project lasers onto the landscape to capture elevation by measuring the distance the laser beam travels, making a composite aerial image that can fairly accurately estimate elevation.
A plane collecting LIDAR data during a flyover.
The LIDAR portion of the data can be analyzed digitally without fieldwork but to get the bathymetric data, I accompanied Giese and Adams on a boat to collect depths for a series of profiles. This involved us heading out in the morning to a cluster of profiles that had not yet been surveyed. We would start with the first line and then slowly trace the profile in each direction, recording depths before going on to the next line as well as the location and azimuth of the profile. The profiles range from Long Point in Provincetown to Nauset Beach in Chatham and aim to survey a cross section from the terrestrial uplands to sub-tidal depths.
A cross section of Profile #68 depicting the full extent of data collected, from the top of the dune to the toe of the beach, beach crest and high water line.
Marindin concluded that the outer banks were eroding at a rate of about 0.8 meters a year, which is roughly still the rate of erosion. Giese and Adams have found that:
Preliminary results confirmed an overall century-scale erosion rate of c. 0.8 m/yr, but unlike earlier studies they indicated that the bluff erosion rate increases alongshore north-to-south by a factor of two. They suggested that this increase and the resulting change in coastal orientation result from the continuing submergence of the Georges Bank shoal on the outer continental shelf southeast of Cape Cod.
The Marindin Project is expected to be completed in 2010 and will yield a more accurate assessment of how much the coastline has eroded since Henry Marindin’s day and give a better sense of the historic paleobathymetric coastal contours.
A profile depicting the former coastline as measured by Marindin (solid brown line) compared to the current coastline (dotted blue line). The difference between these two lines is the amount of erosion this bluff has experienced over the past 120 years.
Find Out More About the Marindin Project
All Hands On Deck- Provincetown Center for Coastal Studies Newsletter
[i] Giese, Graham, and Mark Adams. Cape Cod Shoreline Change and Resource Protection. Prop. Provincetown Center for Coastal Studies and Cape Cod National Seashore (U.S. National Park Service).
[ii] Marindin, Henry L., 1889, Encroachment of the Sea Upon the Coast of Cape Cod, Massachusetts, as Shown by Comparative Studies. Cross Sections of the Shore Between the Cape Cod and Long Point Lighthouses, App. 9, 1891. Cross Sections of the Shore of Cape Cod Between Chatham and Highland Lighthouse. Annual Reports. US Coast and Geodetic Survey, App. 12, pp. 403-407, App. 13 , pp. 409-457.
[iii] Giese, Graham, and Mark Adams. Cape Cod Shoreline Change and Resource Protection. Prop. Provincetown Center for Coastal Studies and Cape Cod National Seashore (U.S. National Park Service).
[iv] “Land-Sea Interaction.” Provincetown Center for Coastal Studies. Web. 21 Nov. 2009. <http://www.coastalstudies.org/what-we-do/land-sea/index.htm>.
