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DEP Wetlands (1:12,000) - April
2007
As of the December 2006 update, this
layer is now complete statewide! See the status
map. |
OVERVIEW
The DEP Wetlands datalayer comprises
two feature types, polygons and arcs (lines). The attribute codes in the
polygon layer describe different types of wetland environments and
the arc attributes describe line types based on adjacent polygon
types or arcs defined as hydrologic connections.
These
layers enhance and replace the layers formerly known as 1:5,000
Wetlands and Streams.
Enhancements/changes
include:
- The features are now seamless, no longer tiled by
orthophoto quad index boundaries. Features are split along OQ
tile boundaries only where attributes are different; this occurs
in a small number of features.
- Distribution is now by Watershed tiles, not by OQ
tile.
- New items have been added to the 2 attribute
tables, including PALIS and PWSID information, and codes
(POLY_CODE, ARC_CODE) for more generalized symbolization,
similar to the codes in the 1:25,000 Hydrography layers.
Area attributes (square feet
and acres) are included for polygons. (See the "ATTRIBUTES"
section below).
- For the arcs, the "streams" from the old layer are
coded as hydrologic connections, and other features are included
as well, like shorelines and apparent wetland limits.
- The scale description in the layer name - 1:12,000
- represents that of the original stereo color-infrared
photography used in the interpretation.
The features
that were in the old layers were copied into the new layers and
then processed to produce the above
changes.
MassGIS stores the two layers in an
Oracle-based ArcSDE format. They are named WETLANDSDEP_POLY
and WETLANDSDEP_ARC. Additionally,
two annotation layers featuring polygon labels is also maintained,
named WETLANDSDEP_A_WET (black text)
and WETLANDSDEP_A_WET_YELLOW (with
yellow text for plotting atop ortho imagery).
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View these
Wetlands online METHODOLOGY
The wetlands are
interpreted from 1:12,000 scale, stereo color-infrared (CIR) photography
by staff at UMASS Amherst. The photography was captured in 1990, 1991,
1992, 1993, 1999 and 2000. See the CIR Map for dates
of the photography.
The interpretation is field checked by Department of Environmental
Protection (DEP) Wetlands Conservancy Program (WCP). Completed
interpretations are then scanned and converted into rectified polygons
and lines using standard photogrametric techniques by a consultant under
contract to the WCP. Final quality control is performed by WCP GIS
staff. The polygons and arcs are merged into a single layer (in coverage
format) and additional attributes are added for the polygon features.
The arc features are coded based on the adjacent polygon types, and
attributes are added to the annotation subclass wet. An overlay process
using the 1:25,000
Hydrography layer codes the PALIS_ID and PWSID
attributes.
The coding of the PALIS_ID and
PWSID attributes was done using an overlay process and was not subject
to the same quality control as the 1:25,000 Hydrography layer. Areas of
wetlands in this layer may be shown as open water in the 1:25,000
Hydrography layer and so the coding of the PALIS_ID would not occur.
Lines represented in the old 1:5,000 Streams layer are shown in this
layer as hydrologic connections. These lines are only defined where they
connect the various wetland types. These connections were not delineated
within wetland areas, nor do they depict a complete stream network
outside of wetland areas.
Because the source scale of the
CIR’s is 1:12,000, plotting of open water features at a larger scale
when overlaid onto existing 1:5,000 imagery will reveal areas of open
water that are not delineated as such. It should be noted that the resulting
wetlands shown in this datalayer are for planning purposes only.
Wetlands boundary determination for other purposes, such as the Wetlands
Protection Act MA Act M.G.L. c. 131 or local by-laws, must use the
relevant procedures and criteria.
A small number of coastal polygons
in this layer outside the interpretation area originated from USGS
Digital Line Graphs or data from NOAA. They have WETCODEs of 88 and
POLY_CODEs assigned by DEP GIS staff. The values for IT_VALC and
IT_VALDESC are blank for these
features.
ATTRIBUTES
Wetlands
Polygons
The polygon layer
WETLANDSDEP_POLY attribute table is populated with these
items:
ITEM
NAME |
|
TYPE
(WIDTH)
|
|
DESCRIPTION |
WETCODE |
|
LONG INT
(10) |
|
WETLAND CONSERVANCY
CODES |
IT_VALC |
|
TEXT
(16) |
|
WETLAND LABEL
ABBREVIATIONS |
IT_VALDESC |
|
TEXT
(20) |
|
DESCRIPTION OF WETLAND
LABELS |
POLY_CODE |
|
LONG
INT
(10) |
|
SIMPLIFIED POLY CODE
ADAPTED FROM 1:25000 HYDROGRAPHY |
PALIS_ID |
|
LONG
INT
(10) |
|
DEP PALIS ID FROM 1:25000
HYDRO (PONDS AND LAKES IDENTIFICATION
SYSTEM) |
PWSID |
|
TEXT
(11) |
|
DEP PWSID FROM PUBLIC WATER
SUPPLY LAYER AND 1:25000
HYDROGRAPHY |
SOURCE |
|
TEXT
(12) |
|
ORIGINATOR OF
FEATURE |
SOURCE_SCALE |
|
LONG
INT
(8) |
|
SOURCE SCALE OF
FEATURE |
AREAACRES |
|
DOUBLE |
|
AREA OF THE FEATURE IN
ACRES |
AREASQMI |
|
DOUBLE |
|
AREA OF THE FEATURE IN
SQUARE MILES
|
The following types of wetlands
are represented in the datalayer:
WETCODE |
|
IT_VALC |
|
IT_VALDESC |
1 |
|
BA |
|
COASTAL BANK BLUFF OR SEA
CLIFF |
2 |
|
BB |
|
BARRIER BEACH
SYSTEM |
3 |
|
BE |
|
COASTAL
BEACH |
4 |
|
BG |
|
BOG |
5 |
|
CB |
|
CRANBERRY
BOG |
6 |
|
D |
|
COASTAL
DUNE |
7 |
|
DM |
|
DEEP
MARSH |
8 |
|
M |
|
SHALLOW MARSH, MEADOW, OR
FEN |
9 |
|
OW |
|
OPEN
WATER |
10 |
|
RS |
|
ROCKY INTERTIDAL
SHORE |
11 |
|
SM |
|
SALT
MARSH |
12 |
|
SS |
|
SHRUB
SWAMP |
13 |
|
TF |
|
TIDAL
FLAT |
14 |
|
WS1 |
|
WOODED SWAMP
DECIDUOUS |
15 |
|
WS2 |
|
WOODED SWAMP
CONIFEROUS |
16 |
|
WS3 |
|
WOODED SWAMP MIXED
TREES |
17 |
|
BB-BE |
|
BARRIER BEACH-COASTAL
BEACH |
18 |
|
BB-BG |
|
BARRIER
BEACH-BOG |
19 |
|
BB-D |
|
BARRIER BEACH-COASTAL
DUNE |
20 |
|
BB-DM |
|
BARRIER BEACH-DEEP
MARSH |
21 |
|
BB-M |
|
BARRIER
BEACH-MARSH |
22 |
|
B-OW |
|
BARRIER BEACH-OPEN
WATER |
23 |
|
BB-SS |
|
BARRIER BEACH-SHRUB
SWAMP |
24 |
|
BB-WS1 |
|
BARRIER BEACH-WOODED SWAMP
DECIDUOUS |
25 |
|
BB-WS2 |
|
BARRIER BEACH-WOODED SWAMP
CONIFEROUS |
26 |
|
BB-WS3 |
|
BARRIER BEACH-WOODED SWAMP
MIXED TREES |
27 |
|
BB-SM |
|
BARRIER BEACH-SALT
MARSH |
88 |
|
N/A |
|
NOT
INTERPRETED |
The codes for the POLY_CODE item
in WETLANDSDEP_POLY are:
POLY_CODE |
|
WETCODES |
|
DESCRIPTION |
1 |
|
9.22 |
|
RESERVOIR (PWSID
CODED) |
2 |
|
4,7,8,20,21,23 |
|
MARSH |
3 |
|
12,14,15,16,24,25,26 |
|
WOODED
SWAMP |
4 |
|
5 |
|
CRANBERRY
BOG |
5 |
|
11,27 |
|
SALT
MARSH |
6 |
|
9,22 |
|
OPEN
WATER |
7 |
|
10,13 |
|
TIDAL FLAT/ROCKY
SHORE |
8 |
|
1,2,3,6,17,18,19 |
|
BEACH/DUNES |
9 |
|
9 |
|
OPEN WATER TIDAL, BRACKISH,
SALT POND
|
10 |
|
9 |
|
OPEN WATER
OCEAN
|
88 |
|
88 |
|
NOT
INTERPRETED
|
Linear
Features
The WETLANDSDEP_ARC
attribute table is populated with these items:
ITEM
NAME |
|
TYPE
(WIDTH)
|
|
DESCRIPTION |
ARC_CODE |
|
LONG INT
(10) |
|
SIMPLIFIED ARC CODE ADAPTED
FROM 1:25000 HYDROGRAPHY |
SOURCE |
|
TEXT
(12) |
|
ORIGINATOR OF
FEATURE |
SOURCE_SCALE |
|
LONG INT
(8) |
|
SOURCE SCALE OF
FEATURE |
The codes for the ARC_CODE item
in WETLANDSDEP_ARC are:
ARC_CODE |
|
DESCRIPTION |
1 |
|
SHORELINE |
2 |
|
CLOSURE
LINE |
3 |
|
APPARENT WETLAND
LIMIT |
7 |
|
HYDROLOGIC
CONNECTION |
8 |
|
MEAN LOW WATER
LINE |
88 |
|
EDGE OF INTERPRETED AREA,
EXCEPT
OCEAN
| A closure line is defined as a boundary
between similar polygon types that has no linear significance.
Polygons with a POLY_CODE of 2 or 3 are considered the same so lines
between them are coded as closure lines.
Annotation
The IT_VALC codes are
incorporated as annotext in the ArcSDE layer
WETLANDSDEP_A_WET.
Note that theese hydrography layers do not have
feature names (e.g., "Quabbin Reservoir" or "Connecticut River") as
attributes. To label the features in these layers, use the annotation in
the HYDRO subclass of the Geographic Place Names
layer.
MAINTENANCE
This datalayer is being
developed by the DEP GIS group. Distribution is through MassGIS.
Questions may be directed to DEP Wetlands Conservancy Program at
617-292-5907.
Individual tile completion dates are
stored in the DATEWET item in the statewide Orthophoto Index
layer.
In the March 2006 update, the following
coding changes were made: ARC_CODE 99 no longer exists, as all OQ index
tile boundaries have been removed and all features edge-matched and
dissolved based on attributes, and attribute discrepancies have been
resolved. ARC_CODE 88 defines the edge of the layer except for ocean
areas. Two POLY_CODEs were added as the open water areas have been
further broken down with areas of tidal influence or salt ponds given a
POLY_CODE of 9 and areas considered open ocean given a POLY_CODE of 10;
the wetcode remains the same (9). Additionally, features outside of the
delineated areas have been removed, though no clipping or extending to
the state boundary has been done. The coding for reservoirs was checked
against the USGS 1:25,000 Hydrography coding and is accurate. The coding
for Palis_ID was checked also, but is still not considered to be
complete. Two areas of missing data on the east and west sides of the
Quabbin Reservoir project area have been completed. With the December
2006 update the layer is complete statewide; this updated filled in
pieces of tiles 197918 and 197922, which cover parts of the towns of
Ayer, Groton, Harvard, and Littleton.
In January 2007 some missing arcs and a
missing polygon comprising open water in the Housatonic Watershed were
added. In April 2007 edits were mode to coastal areas (both polygon and
arc layers). All watershed-based shapefiles along the coast and the
statewide shapefiles were replaced on the MassGIS ftp site at this
time.
For other hydrographic features, also
see the Hydrography
(1:25,000), Hydrography (1:100,000)
and Major Ponds and Major
Streams layers. Also see the Title 5 Setback Areas
layer.
Last Updated 4/9/2007 EOEA Disclaimer | Privacy
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