Dan Nally
Assignment 8
Project Goals
The nutrient release and impervious area associated with various land uses in a watershed
are major determinants of water quality. Development within riparian areas, or vegetated
buffers surrounding wetlands, can be especially detrimental to aquatic and terrestrial
ecosystems. My final project will examine and show visually, spatial and temporal
changes in land use in the Salem Sound watershed.
A temporal analysis will examine human alterations to naturally vegetated land occurring
between 1971, 1985, 1999, and possibly 2005. The spatial component will focus
specifically on those land use changes occurring in riparian areas. As a final piece, I will
estimate the buildout potential of riparian areas based on 2005 land use and zoning data.
The results of each analysis will be broken down by drainage sub-basins within the larger
watershed, so that areas can be prioritized for conservation or restoration efforts.
Some of the results may be incorporated into a report on urban pond management being
prepared for Salem Sound Coastwatch.
Data
Data Layer
Hydrography 1:25,000
Source
MassGIS
Land Use 2005
MassGIS
Land Use 1971-1999
MassGIS
Protected and Recreational Open Space MassGIS
Salem Sound Watershed
Salem Sound Coastwatch
Drainage Sub-basins
MassGIS
Zoning
MassGIS
Soils
MassGIS
SSURGO Soils Data Table NRCS Soil Data Mart
FEMA Q3 Flood
MassGIS
Analysis Steps
Synchronizing Land Use Data
Using a series of selections by attribute and the field calculator, the 37 land use categories
in the 2005 data will be reclassified into the 21 categories used for all previous years
(note: differences in resolution for 2005 data may present problems in making a direct
comparison to other years, in which case it will be excluded from the data). For display
purposes, I will aggregate the land uses into the following categories: agriculture, forest,
open, recreational, urban, and water.
Identifying Riparian Areas
The riparian areas will be a composite of:



FEMA Q3 100 year flood plain (Flood Insurance Risk Zones A and AE)
Hydric Soils based on SSURGO HYDCOMP table from NRCS Soil Data Mart
A 33 foot buffer around all wetlands
This method was borrowed from Lathrop and Haag 2007. I will intersect the resulting
riparian area with land use and drainage sub-basins so that all information is in a single
attribute table.
If I experience major difficulties with this method, or if it fails to provide an accurate
representation of the riparian area, I will instead use a simple 300 foot buffer around all
water features.
Tracking Changes in Land Use
The following information will be gathered by selections by attribute and entered into an
excel table:


For each year, acres of agriculture, forest, open, recreational, urban, and water
Net change in each of the above land use categories between years
The net changes will be displayed by graphs. Next, I will map changes in time by
selecting by attribute and creating new layers for all land use polygons converted from
open land to developed land between each year interval. I will display these layers on
one map in different colors to show the progression through time.
Buildout Analysis
1) Create a layer of developed land (land use categories 8,9,10,11,12,13,15,16,18,19,20)
2) Erase developed land from zoning layer
3) Erase permanently protected open space
4) The remaining land provides a rough estimate of land remaining for development
5) Calculate undeveloped area by drainage sub-basins and within riparian areas
Method adapted from EOEA buildout analysis (http://www.mass.gov/mgis/buildout.htm).
Comparing Drainage Sub-basins
Some of the statistics will be summarized by drainage basins and riparian areas. I have
some ideas, but I’m not entirely sure how to do this part.
Products
1) 3-4 MAPS showing land uses aggregated into the following categories agriculture,
forest, open, recreational, urban, and water for the years:




1971
1985
1999
2005
2) 2-3 GRAPHS showing net changes in the following land use categories: agriculture,
forest, open, recreational, urban, and water, between:



1971-1985
1985-1999
(1999-2005)
3) A MAP showing pre-existing development and new development classified by the
following periods:



1971-1985
1985-1999
(1999-2005)
4) A MAP comparing the rate of development (acres of new development / square mile)
between drainage sub-basins for:

1985-1999 (or 1999-2005)
5) A TABLE showing gross acres of new development and rate of development across
drainage sub-basins for both:


riparian areas
the entire watershed