Hillevi Jaegerman
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Final Paper
GIS-extension
Project description:
The effects of Sea Level Rise (SLR) along the coast of the United States will be
highly variable. Some areas will be less impacted because of their steep incline in
elevation. Massachusetts is not considered as high a concern as low elevation states with
easily eroded coasts like Florida. Though Massachusetts is expected to fare reasonably
well in the next century, studies predicting coastal changes due to sea level rise show
alarming changes to the state’s coast. This project examines some of the northern
counties of Massachusetts that have, to this author’s knowledge, received less attention
plausibly due to their non-critical Coastal Vulnerability Index rating. I wished to do an
analysis of conservative sea level rise predictions in Suffolk, Norfolk, Middlesex, and
Essex counties to show impending changes to coastal communities considered low risk. I
have focused specifically on salt-marsh habitat loss in Essex County and several socioeconomic variables at risk in the state capital, Boston, Massachusetts.
Data Layers and Sources:
MA Hydro poly 25k. Shapefile. Source: M Drive (2009?), MassGIS
MA Beaches. Shapefile. Source: M Drive (2009?), MassGIS
MA Beaches. Shapefile. Source: M Drive (2009?), MassGIS
MA Coastal Zone Poly. Shapefile. Source: M Drive (2009?), MassGIS
MA Wetlands Poly. Shapefile. Source: M Drive (2009?), MassGIS
MA Counties Poly. Shapefile. Source: M Drive (2009?), MassGIS
MA Towns Poly. Shapefile. Source: M Drive (2009?), MassGIS
Boston City Blockgroups. Shapefile. Source: MassGIS
Boston Assessor Parcels. Shapefile. Source MassGIS
Census 2000 SF1 and SF3 Deomographic Data from American Fact Finder.
Source: US census Bureau, http://factfinder.census.gov
Image Elevation file 1:100000 clip. Img_elev2005_fb_Clip.img. Raster File.
Source: Barbara Parmenter (2005).
Atlantic Coast: Coastal Vulnerability to Sea Level Rise. Arc’e00’ export.
Shapefile. Source: USGS. (2001?)
http://kai.er.usgs.gov/regional/contusa/eastcoast/atlanticcoast/data.html
Methodology:
1) All layers were added to the map project.
2) The geographic coordinate system was set to GCS_North_American_1983
3) I projected each layer file to
NAD_2983_StatePlane_Massachusetts_Mainland_FIPS_2001
4) I interactively selected the four northern coastal counties of Essex, Middlesex
Suffolk and Norfolk and created a layer from the selection
a. I clipped the vector shapefiles for Massachusetts Hydro, Wetlands, and
Towns to limit them to the ‘study area’ counties
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b. The Raster file for elevation was also clipped to the four northeastern
counties to make it a manageable extent.
5) I added the field ‘gridcode’ to the raster DEM imagery file attribute table.
a. I used the spatial analyst tools to reclassify the DEM raster to values of 0’5’ to gridcode 1, layers of elevations from 5.0’-10’ to gridcode 2 and from
10’ and up for gridcode 3 respectively. Between 0” and 5” in elevation is
expected to be inundated by projected sea level rise, while areas between
5” and 10” will be influenced. Areas greater than 10” in elevation are
unlikely to be affected in the near future.
b. I converted the raster layer to a vector layer using the gridcode field. I
mapped elevation categorically using the inundated, influenced and not
affected values.
6) Parcels were selected by attribute where the gridcode value of the elevation vector
shapefile was 1 or 2. In other words, I selected areas affected by sea level change
based on modest predictions and isolated them for further analysis. Parcels of
Boston, Massachusetts were selected by location as one method to determine the
potential economic loss likely to occur after SLR. A parcels layer was made to
include only parcels that contained areas influenced or inundated by the projected
SLR (parcels with points at elevations lower than 10 feet). Parcels that contained
both influenced and inundated areas were counted only once in the analysis.
7) For further exploration of economic loss, and to address social/human
vulnerability, I used U.S. Census Bureau data by block groups for Boston,
Massachusetts. Block groups represent the smallest and therefore most exact
recordings for the Census 2000 data. The block groups were selected in the same
manner as the parcels described previously.
8) I joined census block groups with corresponding .dbf tables using their common
field, LOGRECNO
9) The coastal vulnerability index (CVI) base map was created using a compiled
table from Woods Hole Oceanographic Institute. The CVI was calculated by
researchers with USGS and Woods Hole Oceanographic Institute based on a
number of variables (a-geomorphology, b-coastal slope, c-relative sea-level rise
rate, d-shoreline erosion/accretion rate, e-mean tide range and f-mean wave
height) using the following equation: CVI=√((a*b*c*d*e*f)/6) (Thieler et al.
1999).
10) Lastly, marshes and beaches were overlaid on the coastal towns of Massachusetts
using layer files from Mass GIS. The marshland in Essex County comprises the
greatest continuous area that I evaluated to be inundated by SLR.
Difficulties Encountered
The main difficulty I encountered was managing the massive elevation file in the
ArcGIS software long enough to clip it. The system had to reboot so many times we
ended up finding an alternative, less precise (1:100000), layer file. This was unfortunate
since the elevations I was focusing on were between 0 and 10 feet; I would have like
more precise elevation measurements. I also would have liked to have done this project
in my home state, but Maine does not seem to have a complete and open GIS library
online.
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Concluding Thoughts, Results, and Discussion
It is interesting completing this project in 2012, having started it a year ago
because estimates of SLR have increased dramatically in the last year. The estimates I
used for the purpose of GIS analysis were purposely on the conservative side of the
estimates that I encountered. I wanted to show what SLR might look like in an expected
best-case scenario. It would be interesting to continue the evaluation of the
Massachusetts coast using worst-case scenario and disaster-predictive data.
I also found it interesting that examining the coast using the Coastal Vulnerability
Index led to an area exhibiting no effect from SLR in Northern Massachusetts but using
elevation values alone yielded worrisome results. It is important to keep in mind that
analysis based on elevation alone does not account for terrain barriers (Xingong 2009) or
for inland water bodies (though I excluded these from my analysis by deleting values
where elevation was less than 0). Neither system gives a complete picture of what sea
level change will look like. However, the CVI that I used indicates Boston will not be
affected and that clearly is misleading. I think it is clear that SLR will have a great
impact on the lives of those living in coastal communities. GIS and mapping projects can
provide us with a spatial and temporal picture of our future coasts. Ideally, future work
can include GIS analysis in the establishment of an environmental management plan.
Annotated Citations:
Abel, David. “Rising sea level a threat in East, study says”. The Boston Globe. June
25th, 2012, as appeared on boston.com
This was a striking newspaper article that exemplifies how sea level has affected
more of the coast, at a faster pace, than we ever expected. The article discusses Boston
properties in the building process that are addressing slr in their initial design plans.
According to the article, the sea level in Boston has risen nearly a foot already in the last
century.
Hammar-Klose E.S., Pendleton, E.A., Thieler, E.R, Williams, SJ., “Coastal
Vulnerability Assessment of Cape Cod National Seashore (CACO) to Sea-Level
Rise, U.S. Geological Survey”. Open file Report 02-233 (2003)
http://pubs.usgs.gov/of/2002/of02-233/
This report by the USGS helps explain components of the Coastal vulnerability
Index rating system. It is an evaluation of the Cape Cod National Seashore based on
geographically specific factors such as potential for erosion, wave action, and predicted
sea level change. In this paper, the data is ranked and a level of vulnerability at a specific
location can be assessed- the authors suggest this method can be used at any coastline
where there is sufficient GIS data. They collected their data input from state and federal
agencies and table 2 is an efficient and helpful method of displaying each layers’ data
source (for example, they used National sea level change data and mean tide range from
NOAA and a aerial photography layer from MassGIS). They found 24 percent of the
mapped CACO to have a high vulnerability ranking. They conclude that landforms with
the lowest coastal slopes are often the most vulnerable. They demonstrate each variable’s
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influence and the cumulative CVI ranking in figure 11, which uses GIS to create a map
and adjoined color bars to represent each variable along each raster of the shoreline grid.
Xingong Li, Rex J. Rowley, John C. Kostelnick, David Braaten, Joshua Meisel, and
Kalonie Hulbutta. “GIS Analysis of Global Impacts from Sea Level Rise”
Photogrammetric Engineering and Remote Sensing”. 75 no. 7 (2009) 807-818.
This paper examines Partially Inundated Areas (PIAs) on a global scale. The
researchers delineated the PIAs and then assed risk to the populations, the natural and the
built structures of numerous global environments. They used GIS to flag cells below a
projected sea level if, and only if, they had connectivity to the ocean. Those cells with
lower altitudes than future oceans but without the connectivity were excluded from that
method. They also used a second method to delineate raster cells below projected sea
level. The methods that they used yielded fairly similar results. When they determined
their partially inundated areas, they calculated the overall area, land cover and population
numbers within cells- a challenge considering the raster cells distributed globally are not
uniform size.
Titus, James G. “Greenhouse effect and local Wetlands Policy: How Americans
could abandon an area the size of Massachusetts at minimum cost”. Environmental
Management. 15 no1. (1991) 39-58.
This is a policy paper and I don’t necessarily agree with many of Titus’ proposals.
It was useful in its discussion of the effects of Sea Level Rise in salt marshes. Much of
his paper deals with the legal obligations, costs, and fiscal burdens of buying land that is
likely to be inundated by sea level rise.
Thieler, Robert E., and Erika S. Hammar-Klose. “National Assessment of Coastal
Vulnerability to Sea-Level Rise: Preliminary Results for the U.S. Atlantic Coast”.
U.S. Geological Survey Open-File Report 99-593. Woods Hole, Massachusetts
(1999).
This USGS report is related to the source Hammar-Klose et al. but it focuses more
generally on the East Coast rather than the cape. The authors see high risk in the midAtlantic and low risk in the northern coastline of New England. New England’s rocky
shore help prevent erosion which is a variable that positively corresponds with the CVI
index rating.
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