A stream channel geomorphic survey measures the shape, slope, and bed composition of a stream channel, usually over time to track changes.
The surveys conducted by Montgomery County consist of the following:
A survey of the stream bed elevation along the thalweg, or deepest point in the stream.
A survey at a specific cross-section along the stream channel.
Provide information on particle size distribution of the stream bed.
Measures of sinuosity
The sinuosity ratio is the distance between two points on the stream measured along the channel divided by the straight line distance between the two points.
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Why is Stream Channel Surveying Important?
Geomorphology surveying allows us to depict how the stream channel changes (or remains stable) in response to natural and anthropogenic (human-caused) influences. Repeated measurements at a specific study area allow for direct comparison of the features of the stream channel over an extended period of time.
A longitudinal profile depicts the down slope gradient of the stream. Measurements of the longitudinal profile taken over time can document trends in aggradation (sediment build-up) or degradation (erosion). Looking at these trends, we can see how disturbances such as floods or increased sediment inputs from land-use modify the channel bed topography. The longitudinal profile shows features such as riffles, runs, and pools and can be used to generate a "roughness" number, or a measure of the streams ability to dissipate energy. Typically, biological diversity is greatest when a variety of feature types are present (i.e., a combination of riffles, runs, and pools).
Longitudinal profiles, in combination with cross-sectional profiles, are useful in determining the vertical dimension of channel morphologic features. Over time, repeated surveys show how the stream channel adjusts (horizontally and vertically) to accommodate the various flows it handles.
Channel sinuosity is important because it reflects the stream’s adjustment of its slope to the valley slope. The more sinuous a stream is, the more gentle the valley slope.
Pebble counts can show shifts in stream bed material composition over time. For example, a stream may go from having mostly large, cobble size particles, to having mostly sand and gravel size particles as the stream aggrades (fills in).
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Stream Channel Surveying Activities
Montgomery County DEP conducts annual geomorphic surveys at 17 separate areas to assess stream channel characteristics. The surveys are performed as part of the requirements for the state NPDES permit. They provide an effective tool for tracking changes to the stream channel that result from natural occurrences and changes in land use; both of which can have profound effects on the morphology of the stream.
Most of the study efforts to date have focused on the Clarksburg Special Protection Area since it offers the County a unique opportunity to observe changes in the morphology of the stream channel in response to surrounding land use changes. What we learn from indepth study in the Clarksburg SPA will be applied elsewhere in the County as we set the standard for future development requirements to mitigate environmental impacts.
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Data and Data Requests
DEP stream channel survey data is entered into the Ohio EPA Qualitative Habitat Evaluation Index data forms, which log information on the following worksheets:
- Introduction – information about the spreadsheet.
- Summary – information about the study reach (name, date, location, drainage area, etc.)
- Profile – longitudinal slope profile.
- Pattern – calculation of sinuosity.
- Materials – channel bed materials (pebble count information).
- Dimension – cross-sections.
Submitting a Data Request
If you are interested in obtaining data or protocols, please contact DEP at firstname.lastname@example.org. In your request, please provide the following information:
Name, organization (if applicable), phone number, and/or email address
Type of data requested
Time frame requested
Explanation for use of data (helps to personalize the data request)
Preferred method of data retrieval (email, CD by mail, FTP, pick up CD or materials from DEP offices)
Spreadsheet Tools for River Evaluation, Assessment and Monitoring from Ohio Department of Natural Resource Modules
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