Riparian Corridors are defined
as 100 meter corridors encompassing perennial stream and river features
as coded within the MassGIS 1:25,000 hydro datalayer. This layer,
RIP-COR, is stored in the Watershed library with each tile's coverage named
RIPC. In ArcSDE the layer is named RIPARIANCOR_POLY.
The
identification of Riparian corridors has been highlighted as a priority
in numerous conservation planning efforts, including the Massachusetts
Resource Identification Project (MRIP). The MRIP 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.
Field verification is recommended as a "next step" in the planning process.
Overlaying the MassGIS hydro wetlands
data is recommended for proper interpretation of this data. For example,
a 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. For proper display
and analysis of the data select the item INSIDE = 100.
Riparian corridors enclose
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 it's 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:
Lines with minor_num codes 412,
412007, 412009, 412020, 412609
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 rivers edge as opposed to mud flat) and
then deleted. The stream network (perennial streams, rivers
and selected ponds) was buffered 100 meters on each side of the line features
and 100 meters from the edge of polygon features.
