A Landscape-Based Ecological Classification System For River Valley Segments in Lower Michigan (MI-VSEC Version 1.0)
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1997-12-31
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Seelbach, Paul W, Michael J Wiley, and Jennifer C Kotanchik. “A LANDSCAPE-BASED ECOLOGICAL CLASSIFICATION SYSTEM FOR RIVER VALLEY SEGMENTS IN LOWER MICHIGAN (MI-VSEC VERSION 1.0).” Fisheries Research Report 2036 (December 31, 1997). https://www.michigandnr.com/publications/pdfs/ifr/ifrlibra/research/reports/2036rr.pdf
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Abstract
Through ecological classification, researchers both (1) identify and (2) describe
naturally-occurring, ecologically-distinct, spatial units from a holistic perspective. An ecological
river classification involves the identification of structurally homogeneous spatial units which
emerge along the channel network as a result of catchment processes interacting with local
physiographic features. Our observations of Michigan rivers suggest that the natural ecological
unit, as defined by the spatial scales of riverine physical and biological processes, is most closely
approximated by the physical channel unit termed the valley segment. Valley segments are
generally quite large, and characterized by relative homogeneity in hydrologic, limnologic,
channel morphology, and riparian dynamics. Valley segment characteristics often change
sharply at stream junctions, slope breaks, and boundaries of local landforms. We followed
several steps in developing an ecological classification for the rivers of lower Michigan. Step 1 –
We first selected catchment size, hydrology, water chemistry, water temperature, valley
character, channel character, and fish assemblages as fundamental attributes to describe
ecological character of river valley segments. Steps 2-3 – Two experienced aquatic ecologists
worked together, interpreting map information on catchment and valley characteristics from a
GIS, using their combined knowledge of ecological processes and interactions. We initially
examined several key maps to become familiar with the general landscape patterns of a
particular catchment; and to then identify initial valley segment units as defined by catchment
and valley characteristics, and fish assemblages. Boundary definition required the integration of
terrain features observed on several thematic maps (e.g., major stream network junctions, slope
breaks, boundaries of major physiographic units or land cover units; or changes in stream
sinuousity and meander wavelength patterns, riparian wetlands, or valley shape), combined with
knowledge of fish distributions. We next developed categorizations for each component attribute and assigned category values for attributes to each segment unit. Assignments were based on
map-interpretation rules drawn from modeling, survey data, and field experiences. Step 4 – our
results were stored as a map and a table in ArcView 3.0 format. In all, we partitioned and
classified the 19 largest river systems in lower Michigan. Summaries of the attributes assigned to
over 270 river valley segments (covering mainstems and major tributaries) provided an initial
description of the river resources of lower Michigan. Managers of lower Michigan rivers will be
able to develop many of their thoughts and activities within this framework of ecological units.
Development of this system is intended to be ongoing; with the extension of coverage to upper
Michigan, the continued validation of attribute codings, and the addition of new attributes.