Dan Nally
Assignment 6
Project Description
My final project will analyze spatial and temporal changes in land use in the Salem
Sound watershed. The nutrient runoff and impervious area associated with various land
uses is a major determinant of water quality. The loss of riparian areas, or vegetated
buffers surrounding wetlands, can be especially detrimental to aquatic and terrestrial
ecosystems. A temporal analysis will examine human alterations to naturally vegetated
land over the years of 1985, 1999, and 2005. The spatial component will focus
specifically on land use changes occurring in riparian areas. The results of each analysis
will be broken down by sub-basins within the larger watershed, so that areas can be
prioritized for conservation or restoration efforts.
While the land use analysis will comprise the core portion of the study, if time allows, I
would like to investigate two related elements as well:
1) To determine whether land use is an accurate predictor of water quality by
exploring the relationship between land use and pollutant levels (nitrogen and
phosphorus) observed at downstream DEP DWM monitoring stations; and
2) Estimate watershed’s buildout potential based on zoning classifications,
highlighting areas with the greatest potential for growth.
Some of the results will be presented as part of a larger report on urban pond
management being prepared for Salem Sound Coastwatch.
Methods
Whole Watershed Land Use:
1) Clip Land Use layer by Salem Sound watershed. Generate area statistics and compose
maps based on use classifications from 1985, 1999, and 2005 data. (Use classifications
must first be synchronized across observation years due to an increase in categories for
2005 data). Clip Land Use again by sub-basins and compare changes between them. I
would like to create generalized land use maps from each year as well as a map clearly
depicting recently developed or protected areas.
Riparian Area Land Use:
2) Create a polygon layer covering the riparian area around all wetland features. I may
do this one of two ways: 1) a “full” riparian zone based on hydric soils, wetlands, and
floodplains; or 2) a simple 300 foot buffer around rivers and streams. Since either of
these layers will need to be created in multiple steps, I will use the merge tool to create a
single polygon representing the riparian zone. I will then clip the Land Use layer by the
riparian polygon and perform a similar analysis to the previous step.
Water Quality and Land Use:
3) Select a few DEP water quality monitoring stations within the watershed. (I will have
to confirm if are any of these in the watershed, but I assume that there must be).
Determine if land use in contributing areas correlate with higher nitrogen and phosphorus
levels downstream. Contributing areas may be determined by:
1) Using the DEM Elevelation Layer: create and Flow Direction layer with filled
Sinks Use the Watershed Tool with DEP sites as pour points to delineate the
contributing area of each; or
2) More simply, but less accurate, choose one monitoring site per sub-basin.
Buildout Analysis (whole watershed)
4) Clip zoning by Salem Sound watershed. Using the Land Use/Zoning Crosswalk
method referred to on the MassGIS website
(http://www.mass.gov/mgis/landuse_stats.htm), and discussed in more detail at
(http://commpres.env.state.ma.us/content/buildout.asp)
to aggregate land use and zoning into a single layer showing maximum potential
buildout. Determine what uses unprotected open land could become in the future.
Examples of Similar Studies
Ekness, P., Randhir, T. (2007). Effects of Riparian Areas, Stream Order, and Land Use
Disturbance on Watershed-Scale Habitat Potential: An Ecohydrologic Approach to
Policy. Journal of the American Water Resources Association, 43 (6), 1468-1482.

Ekness and Randhir examined spatial-temporal relationships between water resources
and the quality of the surrounding habitat in the Westfield watershed in Western
Massachusetts. A GIS analysis based on GAP data for species diversity and MassGIS
land use datalayers showed that habitat potential is highest in riparian zones,
headwater areas, and lower order subwatersheds. The article posits that water quality
improvements can be made more efficiently through conservation policies that
encourage wider and variable width riparian zones, protect headwaters and lower
order subwatersheds, and minimize disturbances in riparian/headwater areas.
Haag, S.M., Lathrop, R.G., (2007). Assessment of Land Use Change and Riparian Zone
Status in Barnegat Bay and Little Egg Harbor Watershed: 1995-2002-2006.

I plan to use this report as the primary model for my project. Haag and Lathrop used
land use data from 1995, 2002, and 2006 to monitor the development of riparian areas
in the Little Egg Harbor Watershed in New Jersey. The land use analysis used two
measures of riparian zones: 1) a “full” riparian zone based on hydric soils, wetlands,
and floodplains; and 2) a simple 300 foot buffer around rivers and streams. Results of
the analysis were broken down by sub-basins allowing them to be prioritized by for
remedial action.
Massachusetts Audubon Society. (2009). Losing Ground: Beyond the Footprint.
Retrieved from http://www.massaudubon.org/losingground/download.php

Mass Audubon performed a thorough statewide land use study illustrating the
ecological impacts of sprawl and the need prioritize and coordinate protection efforts
on a regional scale. The report’s s content is effectively displayed by a number of
fantastic GIS figures.
Sliva, L., Williams, D. D. (2001). Buffer Zone Versus Whole Catchment Approaches to
Studying Land Use Impact on River Water Quality. Journal of Water Resources,
35 (14), 3462-3472.

Sliva and Williams evaluated the effects of natural and anthropogenic landscape
characteristics on water quality in Ontario watersheds. The study sought to determine
whether land use near streams is a better predictor of water quality than land use
throughout the entire watershed. The results showed that in both cases, urban land
use was the strongest determinant of water quality. Also, whole watershed landscape
characteristics afforded slightly greater predictability than a buffer zone analysis.
Data Layers
Data Layer
Source
Hydrography 1:25,000
Land Use 2005
Land Use 1991-1955
Soils
Impervious Surface
Protected and Recreational
Open Space
DEP DWM Monitoring
Stations
DEP DWM Related Water
Quality Tables
Digital Elevation Model
1:5,000
Salem Sound Watershed
Drainage Sub-basins
Zoning
MassGIS
MassGIS
MassGIS
MassGIS
MassGIS
MassGIS
Minimum Accepted
Accuracy* (feet)
100
100
100
100
100
100
MassGIS
general area
MassGIS
n/a
MassGIS
10
Salem Sound Coastwatch
MassGIS
MassGIS
200
200
100
* Except where otherwise noted, a minimum accuracy of 100 feet is preferred. Since the
analysis is being performed over a large study area, absolute precision is not required.
100 feet was chosen because this is the width of a typical regulated buffer zone around
wetlands.