Geomorphological Classification for Risk Management of Streams
Field researcher in a stream channel.
Changes in amount and types of land use
in a watershed can destabilize stream channel structure, increase
sediment loading, and degrade in-stream habitat. Stream classification
systems (e.g. Rosgen) may be useful for determining the susceptibility
of stream channel segments to erosion and bank failure, and may
help to identify stable endpoints for stream channel restoration
and best management practice (BMP) placement.
We use this approach to determine if streams can be classified to assess the
risk of increased erosion resulting from changes in land use.
One of the hypotheses associated with the survey work is that
a stream can resist change up to a certain threshold, but
beyond that level the stream will change classifications and
alter both its channel formational and erosional properties. Understanding
these thresholds will assist in the evaluation of risks from development
and aid in the design and implementation of both structural and
nonstructural
BMPs.
Geomorphological data sample interpretation.
Stream classifications are developed based on geomorphological
data, which can be collected by a variety of methods– notably,
intense surveying or interpretation of existing data sets (aerial
photographs and topographic maps). The initial phase of this research
consisted of collecting geomorphic data at several levels of intensity
in terms of both effort and cost for the purpose of determining
minimum requirements for assessing a stream's condition.
It has been found that when aerial photographs and topographic
maps are used to calculate slope and sinuosity, uncertainty
in the values is greater than when these metrics are obtained
by extensive surveying; however, the resulting stream classifications
obtained in Ohio are the same. The accuracy of these values when
confirmed by short site visits is adequate for rapid reconnaissance,
followed by a more intense evaluation of areas identified as having
greater risk factors. This work has been confined to assessment
of data collection methodology (surveying) and data interpretation
(stream classification) at the scale of a stream reach.
Research will focus on three aspects of this work:
- the relationship between the geomorphic metrics and the biological
criteria used to determine impairment;
- the ability of the data collection methods to be expanded
to the watershed scale with identification of specific areas
for more intense review; and
- the applicability of the classification methods to the prediction
of impairment within physiographic ecoregions and among diverse ecoregions.
Contact: Christopher Schultz;
Joseph Schubauer-Berigan;
Matthew Morrison (EIMS#116424)
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