Eric Senecal
Assignment 8 – Project Flow
My project has changed again significantly, but emerged from considering criteria for my
buildable lands project in Portland, ME. No parcel data was available and it was difficult to settle
on criteria. One aspect of that analysis that I was interested in was coastal flood hazards
considering the predicted increase in storm intensities and rise in sea level. I decided to shift
back to Massachusetts and to do a coastal risk assessment of two towns on Salem Sound,
Danvers and Salem.
The goal of this project is to analyze certain coastal flooding risks that Salem and Danvers are
facing and determine which is at greater risk based on property and human exposure to flood
hazards. Recent years have seen serious flooding on the north shore in the towns of Wakefield
and Peabody. Predictions for 30% increase in rainfall in this century due to climate change are
common. At a recent Tufts panel on local effects of climate change, the current 100-year flood
level was described as being approximately a 4-year event when sea level rise due to subsidence,
thermal expansion, and assimilation of continental ice, along with the increased intensity and
frequency of hurricane surges are accounted for. This project takes a simple approach to
comparing the flood risk to exposed parcels and facilities in each town, and the demographic
differences between towns as a way of beginning to compare vulnerability of different
communities to more severe weather events.
Project Steps
Add all layers in 2 data frames (one for each town)
Re-categorize land use, and perform queries, editing, and intersects for each town
Figure out how to analyze connectivity of road network if not too difficult
Create estimate of population affected based on block group data (I thought simple population
data was available at the block level. MassGIS has a block table but it gets added under my block
group layer in the source view and cannot be joined to the block layer)
Calculate areas and percentages of flooded parcels by land use
Create tables, large scale detail area maps, and explanatory text for poster
Finalize maps for poster
Create poster layout
Data Processing Steps
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Select Danvers and Salem interactively out of Town Boundary layer
Add parcel, land use, and demography data at the block group level.
Add and join block group tables for household income, population and age
Select land use polygons and parcels that are within or intersect the town
Add Q3Flood layer – adding 5 flood zone categories including 500-year flood as an
estimate of what may become a decadal scale event.
Select Flood polygons that intersect the town
Add EOT roads layer
Add schools point data
Edit the Land Use 21 layer into broader categories by adding a new field, using the editor
toolbar, and selecting by attributes. Adjust symbology.
 Residential
 Commercial
 Open Space
 Recreational Facilities
 Woods and Brush
 Fresh Water
 Industrial
 Buildable vacant land
 Ag Lands
Union of Land Use and Parcels
Select by location new parcels that intersect flood polygons, or perform intersect.
Select by attribute for different land use parcels and calculate area of each land use in
flood zone, number of parcels of each use, estimate of people in flood parcels based on
population and percent of total population flooded.
Possibly analyze road network flooded by total miles flooded and subsequent reduced
connectivity of existing non-flooded roads.
Look at most flooded block groups by age and income
Do the same for both towns
This project will utilize the querying capacity of GIS, selecting by location and by attribute, both
in creating new selections and from current selections. I will use the editor tool bar to populate a
new parcel and land use field called landuse so that the 21 uses can be categorized. I may use the
intersect tool or clip tool, or may select by location to select flooded parcels depending on which
is more feasible. I will calculate geometry of flooded land use parcels in a new field, probably in
acres. I do not yet know the GIS technique for analyzing connectivity of streets.
This project will result in a map of Danvers and a map of Salem that clearly show the parcels at
risk of potential flooding, symbolized by land use characteristics. Each map will have an
accompanying table detailing the total area and percent area flooded by land use, the number of
parcels and estimate of people affected, the reduced connectivity of roads due to flooding, the
percent of current “buildable vacant land” that would be flooded and should not be built on, the
number of schools affected, and a simple demographic comparison of the two towns. In addition
to the town maps, I will include large scale maps of critically affected areas for each town. A
discussion of the findings and limitations of this simple analysis will be included on the poster,
as well as an overview my thoughts on the need for coastal risk assessment with changes in the
frequency of 100 year flood being predicted. I will also summarize the results to show that two
nearby towns may face different risks, and demonstrate that GIS can be a powerful tool in
analyzing those risks, potentially much more completely.