Natural Land Riparian Corridors
are defined as "natural lands" within a 100 meter corridor encompassing
perennial stream and river features (as coded in the MassGIS 1:25k Hydrography
layer). This datalayer depicts areas within the riparian corridor
that remain in a "natural state", potentially functioning as a corridor
for select species movement, as well as additional ecological purposes.
It is important to note the "natural land" definition and the distance
defining the riparian corridor were tailored to meet the objectives of
the Massachusetts Resource Identification Project (MRIP). The layer
is named NAT-COR and is tiled in the Watershed library, with coverages
named NATC. In ArcSDE the layer is named NATRIPCOR_POLY.
The
identification of riparian corridors has been highlighted as a priority
in numerous conservation planning efforts. Understanding whether
the riparian corridor is functional is a logical next step. One approach
for assessing the functionality of a riparian corridor is to assess whether
it is in a natural condition. The MRIP Natural Lands Riparian Corridor
datalayer represents one iteration, as well as a coarse filter analysis
of these features. The 100 meter buffer distance is a subjective
value derived from existing conservation plans, as well as current literature.
The "natural lands" definition is tailored to meet specific project objectives.
Field verification is recommended as a "next step" in the planning process.
Overlaying the MassGIS hydro wetlands
data is recommended for proper interpretation of these data. For
example, a natural land riparian corridor may appear to be severed within
a landscape when in fact it is simply an area for which the corridor has
ingress to a wetland and egress at another point along the wetland feature.
Wetlands were not included in the definition of riparian corridor.
In addition, an area within the 100 meter buffer distance may not display
as a "natural land" landuse class when in fact it is recognized as a wetland
within the Hydro data set. Attribute item INSIDE = 100 and NAT =
1 should be defined for proper display and analysis of the data.
Riparian corridors consist of two types of spatial data features (arcs
& polygons) and include portions of three general hydro datalayer codes:
perennial streams, ponds, and rivers. A stream (a line feature) may
flow across the landscape increasing in width to include ponds and rivers
(polygon features) along its route. A challenge in creating this
datalayer was to include the polygons coded as ponds and rivers and yet
omit isolated ponds that are not included in the definition of riparian
corridors.
The selection process included:
25k Hydrography arcs with minor_num codes 412, 412007, 412009, 412020,
412609
25k Hydrography polygons with minor_num codes 115, 116, 400 ,
401, 412, 416, 115007, 115020, 115116, 115410, 115412, 115421, 115422,
115616, 412111, 412115, 619412, 421, 421007, 421619, 421625, 421628, 619421,
421625619, 421619625, 619625421, 101, 122, 101619, 101625, 421101, 619101,
101619625
Polygon features (ponds) not part of the stream network were deleted
through an assessment of tnode = fnode. Bays, estuaries, and mud
flats were initially selected for program processing (assuring riparian
buffer from a river's edge as opposed to a mud flat) and then deleted.
The stream network (perennial streams, rivers and selected ponds) was buffered
100 meters from the line features and 100 meters from the polygon features.
The result is a 100 meter buffer from the line features (perennial streams)
and a 100 meter buffer from the edge (arcs) of the polygon features (rivers
& selected ponds).
"Natural Land" categories of the MassGIS landuse datalayer (1985/1991,
MacConnell) were defined as follows:
| Landuse Code |
|
Description |
| 2 |
|
Pasture (extensive agriculuture) |
| 3 |
|
Forest |
| 4 |
|
Non-forested freshwater
wetland |
| 6 |
|
Abandoned agriculture power
lines areas of no vegetation |
| 14 |
|
Saltwater Wetland |
| 20 |
|
Water |
| 21 |
|
Woody perennial |
These selected natural lands were intersected with the Riparian Corridor
datalayer to produce the Natural Land Riparian Corridor datalayer.
