Rocky Coast, Constructed Edge: Tracing Portland’s Land-Sea Habitat Typologies

Anne Clark Baker (MLA I AP)

Project Overview

The goals of this travel research were [1] to create a typological comparison between the morphology of natural rocky coasts and constructed edges such as sea walls, bulkheads and revetments in the intertidal zone of Mid-coast Maine, and [2] to examine the interrelationships between the morphology of these coastal edge typologies and the way in which species occupy them.

Rachel Carson’s book The Edge of the Sea was the starting point for this project. Carson’s work emphasizes detailed and methodical descriptions of the interrelationships between species and the physical morphology of rocky shorelines in Maine. In contrast to the typically rough, sloping rocky coastal morphologies, today’s constructed land/sea edges are often vertical or smooth, lacking the physical capacity to foster the zonal microclimates, pools and crevices required by many intertidal species. Through video, photography, measuring and modeling, the research traces typologies of different natural and constructed edges in mid-coast Maine, focusing on the relationship between the morphology of these edges, and the observed presence or absence of specific species. The research provides a broad entry into the question of how the morphology of land/sea constructed edges might be better designed to create increased opportunities for the creation of habitat for intertidal species.

Project Information

Introduction
The goals of this travel research were [1] to create a typological comparison between the morphology of natural rocky coasts and constructed edges such as sea walls, bulkheads and revetments in the intertidal zone of Mid-coast Maine, and [2] to examine the interrelationships between the morphology of these coastal edge typologies and the way in which species occupy them.
The project was inspired by Rachel Carson’s description of intertidal zones along Maine’s rocky coast in her book The Edge of the Sea (1955), as well as a precedent public installation along sea walls in Sydney, Australia (2010). Rachel Carson identifies the coast Maine as the quintessential rocky coast habitat: its geology, tidal fluctuation levels, and climate make it the ideal site for study of representative rocky coast intertidal species. Her writing reveals a methodical account of the interrelationships between species and the physical aspects of the rocky shore, combined with a reading of the ephemeral and sensory qualities of the intertidal zone, specifically in terms of color and light.
In Sydney, biologist Mark Browne affixed a series of hollow vessels to the smooth face of a seawall. The vessels were installed at varying heights and became filled with tidal water for varying durations of time, achieving cycles similar to those of tide pools in roughly textured and gently sloped rocky intertidal zones. The results of Browne’s installation: snails, anthropods and limpets unable to find habitat on the smooth seawall surface immediately began populating the vessels. Browne’s installation is a clear example of the way in which the morphology of a water-land interface – in this case, vertical and smooth versus a varied surface allowing water to pool for different periods of time – affects the way species inhabit the space. From a human perspective, Browne’s installation became a site of cultural interest and served as a reminder to the public that the coastal waters are full of life.

Regional Context
The Gulf of Maine contains a higher diversity of marine species than temperate coastal regions to the south, largely as a result of the complex geomorphology of the sea floor. It contains three major basins carved by glacial erosion, with depths up to 370 meters below sea level. Cool, slow-moving, high-salinity water gathers in the bottom of these basins, supporting rare soft coral communities. The Gulf’s interior perimeter consists of major bays and an underwater shelf terrain, ranging from 20 to 80 meters below sea level and including highly productive habitats such as salt marshes, kelp, seaweed, eelgrass, and shellfish beds.Offshore, underwater banks force cold, nutrient-rich currents toward the surface, fueling the growth of phytoplankton and zooplankton and attracting larger fish, mammals and birds, making the banks the most productive commercial fishing grounds in the Gulf.
This underwater terrain of shelves and banks delineates the central area of the Gulf as a “sea within a sea.” The Gulf is characterized by seasonal water temperatures, currents, and tidal fluctuations that are distinct from those of the open Atlantic. Subsurface currents move primarily through to two underwater channels, receiving the cold Labrador Currents from the north, while deflecting the warm Gulf Stream currents to the west.The Gulf’s 70,000 square mile watershed situates Boston as its largest urban center and reaches into Quebec at its northwestern extent.

Selected Sites
The area of study for rocky shorelines was located in Penobscot Bay, Maine. This bay shares comparable characteristics of geology, bathymetry, orientation and tidal force to those of Casco Bay, where Portland, Maine is located.   The area of study for constructed edges included locations in both Penobscot and Casco Bays.  Through site observations and discussions with biologists and ecologists, rockweed, which thrives in the mid-littoral tidal zone, became a species of interest in the study overall. The species is important both in terms of its capacity to dampen the force of wave action as well as its role in protecting vulnerable intertidal animals from desiccation or predation through its provision of damp, shaded spaces beneath its fronds at low tide. Among other species such as mussels, barnacles, Irish moss and redweed, this species became the primary indicator for broadly assessing the habitat value of each edge typology. Generally, the presence of rockweed had an inverse relationship to the smoothness and verticality of a surface in the intertidal zone.

Methods
Through video, photography, measuring, sketching and digital modeling, the research traced the physical shape-based typologies of different natural and constructed edges, relating this to the presence or absence of specific species, including rockweed. The research is ongoing and currently provides a broad entry into the question of how the morphology of land/sea constructed edges can be better designed to create increased opportunities for the creation of habitat for intertidal species.

Conclusion
While this travel study was focused in one specific coastal region, it is intended to inform the way we think about – and design – coastal edges in many geographic contexts. The vision behind establishing typologies for case study sites was to create a matrix of indicators through which to better understand different coastal conditions, and to inform and advance the design, engineering and construction of coastal edges. Infrastructural elements such as seawalls and bulkheads can be designed to serve multiple functions, including human and non-human uses, beyond the singular function of the structural protection of land-based human settlements. With over 50% of the total coastline in the United States comprised of constructed surfaces, there are many possible applications and extensions of this exploration.
Contact Information:
Anne Clark Baker
anneclarkbaker@gmail.com

Many thanks to:
Katharine Parsons
Senior Coastal Ecologist, Manomet Center for Conservation Sciences
Lecturer, Harvard Graduate School of Design

Peter Larsen
Senior Research Scientist (Emeritus), Bigelow Laboratory for Ocean Sciences

Seth Barker
Biologist, Maine Department of Marine Resources

Dan Sampson
GIS Data Manager, Massachusetts Office of Coastal Zone Management

Pierre Bélanger
Associate Professor of Landscape Architecture, Harvard University Graduate School of Design

References:
Carson, Rachel. The Edge of the Sea. Boston: Houghton Mifflin Company, 1955. Illustrated by Bob Hines.

Mann, K.H. Ecology of Coastal Waters, A Systems Approach. Studies in Ecology, Volume 8,University of California Press, 1982.

Meerman, Ruben.  Sea Walls. ABC News Catalyst, Interview of Dr. Mark Browne, 2010. http://www.abc.net.au/catalyst/stories/2936248.htm

Moore, P.G. and Seed, R. The Ecology of Rocky Coasts. Columbia University Press, 1986.

Newell, Richard C. Biology of Intertidal Animals. Faversham, Kent: Marine Ecological Surveys, 1979.

Pappal, Adrienne. Marine Invasive Species: State of the Gulf of Maine Report, 2010.

Wilkinson, Tara A.C. et al. Marine Ecoregions of North America. Commission for Environmental Cooperation, 2009.

A Fundamental Unity: Bigelow Laboratory for Ocean Sciences Annual Report 2009-2010

Proctor, Noble S. and Lynch, Patrick J. A Field Guide to North Atlantic Wildlife Marine Mammals, Seabirds, Fish, and Other Sea Life Yale University, 2005.

Mapping Sources:
Multipurpose Marine Cadastre: http://csc-s-web-p.csc.noaa.gov/MMC/#
NOAA DEM Mapper http://csc-s-web-p.csc.noaa.gov/ http://www.ngdc.noaa.gov/mgg/dem/demportal.html
Naval charts by Coast Guard Region http://www.charts.noaa.gov/ENCs/ENCs.shtml
MORIS http://www.mass.gov/czm/mapping/index.htm
Rutgers Marine Resource http://marine.rutgers.edu/
Gulf of Maine USGS http://coastalmap.marine.usgs.gov/
Marine GIS http://www.marinegis.com/dataen.html
NOAA Marine Habitat http://www.habitat.noaa.gov/protection/index.html
NOAA Coastal Geospatial http://coastalgeospatial.noaa.gov/data_gis.html
Atlantic Jurisdictional/Legislative GIS http://www.boemre.gov/offshore/mapping/atlantic.htm#GIS
Massachusetts Ocean Management Plan http://www.mass.gov/eea/ocean-coastal-management/mass-ocean-plan/final-massachusetts-ocean-management-plan.html
Massachusetts Seafloor Mapping Cooperative http://woodshole.er.usgs.gov/project-pages/coastal_mass/html/current_map.html
http://www.northeastoceanviewer.org/
http://northeastoceandata.org/data-catalog/northeast-ocean-data-files/
http://www.scannewengland.net/wiki/index