The Stream Restoration Toolbox

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(No Transcript)
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The Stream Restoration Toolbox
The Stream Restoration Toolbox consists of
current basic research cast into the form of
tools that can be used by practitioners. The
details of a tool are presented through a
PowerPoint presentation, augmented by embedded
Excel spreadsheets or other commonly available
applications. The toolbox is a vehicle for
bringing research findings into practice. While
many tools are being developed by NCED
Researchers, the opportunity to contribute a tool
to the Toolbox is open to the community. For more
information on how to contribute please contact
Jeff Marr at marrx003_at_umn.edu.
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Statement of liability and usage

• This tool is provided free of charge. Use this
  tool at your own risk. In offering this tool, the
  following entities and persons do not accept any
  responsibility or liability for the tools use by
  third parties
• The National Center for Earth-surface Dynamics
• The universities and institutions associated
  with the National Center for Earth-surface
  dynamics and
• The authors of this tool.
• Users of this tool assume all responsibility for
  the tool results and application thereof. The
  readers of the information provided by the Web
  site assume all risks from using the information
  provided herein. None of the above-mentioned
  entities and persons assume liability or
  responsibility for damage or injury to persons or
  property arising from any use of the tool,
  information, ideas or instruction contained in
  the information provided to you.

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Title Page
Tool Title Channel Planform Statistics
Toolbox Tool Author J. Wesley Lauer Author
e-mail laue0050_at_umn.edu Version 1.0 Associated
files 1) PlanformStatisticsTools.ppt 2)
planform_statistics_tools_v91.mxd Date February
2006
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Outline of this Document

• Introduction to the Tool
• Background
• Installation
• Tool 1 Interpolate Centerlines From Two Bank
  Lines
• Tool 2 Lateral Distance Measurement
• Tool 3 Bank Buffer Boxes

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Introduction
The current availability of digital aerial
photography allows for the relatively
straightforward comparison of historic and recent
imagery of river channels. However, making
quantitative measurements of planform
characteristics such as width, curvature, and
channel migration rate, while not difficult, can
be time consuming. These tools automate several
of the more time consuming aspects of these
measurements at discrete points along a
single-thread river.
This image of the Bogue Chitto River, Louisiana,
shows two channel centerlines developed from bank
lines digitized by hand from aerial photography.
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Background
The channel planform statistics tools are a set
of visual basic programs written for ArcMAP 9.1.
The tools have been installed in an ArcMAP map
file named planform_statistics_tools_v91.mxd.
The tools perform three primary functions. 1)
Interpolate the centerline of two lines (i.e. two
banks that have been digitized by hand from an
aerial photograph). Width and local radius of
curvature at each evenly-spaced point along the
centerline are saved in a text file. 2) Measure
the mean lateral normal distances at even
increments between two lines developed using tool
1 (i.e. between river channel centerlines at two
points in time), and 3) generate a polygon
shapefile of boxes adjacent to the channel banks
that correspond with a particular centerline
point. These boxes are useful if the user wishes
to correlate a bank property with one of the
observed statistics. This powerpoint
presentation presents rudimentary instructions
for using the tools. While the instructions are
basic, the tools are fairly intuitive so that the
user should be able to develop useful information
with only a minimal amount of trial and error.
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Installation
The tools have already been installed in the
ArcMAP map planform_statistics_tools_v91.mxd.
Technically, the code is associated with
UItoolcontrol1, UItoolcontrol2, and
UItoolcontrol3 in This Document of the project.
However, these three UI tools have already been
associated with a toolbar in the migration.mxd
map, so no installation should be required to
access the tools, aside from opening the file
planform_statistics_tools_v91.mxd in ArcMAP.
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Tool 1 Interpolate Centerlines From Two Bank
Lines
This tool finds evenly spaced points that are
representative of the center of two roughly
parallel lines. It then connects these points
into a new line. The algorithm used to solve for
the points works as follows The program creates
a point a user specified distance from the
previous point. It then varies the angle ? until
the distance between the closest point on each
respective bank line and the new point is nearly
equal. (i.e. a b). This results in a
relatively smooth centerline made up of evenly
spaced points. The new line is stored in a new
shapefile.
a
a
b
b
q
q
Final
Initial


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Tool 1 Interpolate Centerlines From Two Bank
Lines (cont.)
To use the tool, select the following icon from
the toolbar
The tool prompts the user to select the two lines
between which the centerline is to be
interpolated. These lines should be oriented in
the same direction. It then asks for the spacing
between the interpolated points. The program
seems to run reasonably well when the spacing is
about half a channel width or less. The tool is
relatively stable in that few geometries cause it
to fail. However, it sometimes extends the last
segment past the bank lines. Since channel
width is measured as part of the interpolation
process, channel width at each interpolated point
is saved as a separate text file with the same
name as the shapefile used to store centerline
information.
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Centerline interpolated from two bank lines using
Tool 1.
(1952 photograph, Pearl River, Louisiana/
Mississippi.)
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Tool 2 Lateral Distance Measurement
This tool finds the average lateral normal
distance between the nodes interpolated using
tool 1 and a second line, using a best fit Bezier
curve that is assumed to represent the most
likely path of migration for a particular point.
It stores the length of these curves in a new
polygon shapefile. To use this tool, select the
following icon from the toolbar The tool asks
for the line to which distances are to be
measured, and then for the reference line. It
will also prompt the user for a path and name for
the new shapefile. It is possible that the
program will blunder under certain geometries,
particularly when the line to which measurements
are made ends before the reference line. To make
it obvious when this occurs, the program creates
screen graphics representing each migration
trajectory. If a trajectory looks unreasonably
long, the geometry of the centerlines should be
changed or that measurement should be discarded.
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Tool 2 Lateral Distance Measurement (cont.)
For bends that translate primarily downstream
without changing form, the trajectory of outward
normal migration would change direction, as shown
below. In this case, the program has the
capability of computing the short-term outward
normal migration rate for the reference line
(usually the new centerline position) by fitting
the Bezier curve between a user-defined bend apex
trajectory rather than the historic centerline.
Channel Centerline at t
D
l
di
Channel Centerline at t ?t
, where
The program reports the distance doutputci?t
rather than the rate. Simply dividing doutput by
?t results in a reasonable approximation of the
local migration rate.
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Tool 2 Lateral Distance Measurement (cont.)
The program automatically prompts the user for a
shapefile that represents the set of all bend
apex trajectories. The shapefile should be a
line shapefile in which, for all bends that
translated primarily downstream, straight lines
connecting the apex of the older and newer bend
has been digitized. This line should be snapped
to each of the respective centerlines.
Apex trajectory line. Such lines should be
digitized in a separate shapefile before running
the distance measurement tool. The lines should
be oriented toward the newer centerline, snapped
to each respective centerline, and their forward
projection should not intersect the newer
centerline. If a line is not present at a
particular downstream-translating apex, the
program simply fits Bezier Curves between the two
centerlines.
Channel Centerline at t
Channel Centerline at t ?t
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An example of the correction procedure
An example of the results of the downstream
translation function of Tool 2.
The procedure ensures that the method does
not predict outward migration at downstream
translating bend apices.
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Example usage of tools 1 and 2
Centerline interpolated from two bank lines using
Tool 1, older photograph.
(1952 photograph, Pearl River, Louisiana/
Mississippi.)
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Modern (1998) aerial photograph
Centerline interpolated from two bank lines using
Tool 1, more recent photograph.
(1998 photograph, Pearl River, Louisiana/
Mississippi.)
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Results of tool 2 Measured lateral migration
distances at evenly spaced intervals. (1952
centerline was used as the to centerline so
that measurements would be stored at even
increments along the 1998 centerline.)
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This tool finds areas on each bank that
correspond with a particular channel centerline
point developed using tool 1 (and possibly
migration distance computed using tool 2) and
saves these as two polygon shapefiles (one each
for the left and right banks, respectively). A
polygon shapefile representing the union of each
set of boxes and the region within the channel
corresponding with that set is also saved.
Right Buffer Boxes
Input Bank and Centerline Geometry
Left Buffer Boxes
Union Boxes
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Tool 3 Bank Buffer Boxes (cont.)
The tool creates a sampling corridor of a
user-specified width on the upland side of two
bank lines. The corridor is then subdivided by
projecting evenly spaced lines outward from the
centerline (which should be composed of equally
long line segments-as is the case for a
centerline developed using Tool 1) until they
intersect the offset bank lines. In most cases,
the subdividing lines are projected normal to the
centerline. However, where channel curvature is
greater than a threshold value (10 is
suggested), the inwardly projected subdividing
line is terminated at the point on the outer edge
of the sampling corridor nearest to that
subdividing lines origin. This ensures that
subdividing lines do not miss the edge of the
sampling corridor on the inside of sharp bends.
If the above criteria causes two adjacent
subdividing lines to intersect inside the outer
edge of the sampling corridor, the downstream
line is rotated about its origin on the
centerline until the intersection occurs at the
edge of the sampling corridor.
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Tool 3 Bank Buffer Boxes (cont.)
To use this tool, select the following icon from
the toolbar The user will first be prompted
to select the centerline upon which the boxes
will be based. The user is then prompted for the
buffer thickness and is asked to select two
separate sets of bank lines, each of which should
be visible in the current view. (The banks
should have been digitized in the direction of
flow. The first set of bank lines is used only
to compute the length of bank within the buffer
boxes. The second is used to generate the buffer
boxes. The first and second set of lines may be
identical, but this is not required. Bank lines
must extend past the end points for the
centerline.) The user is next prompted for a
maximum expected distance between the channel
centerline and the outer edge of the buffer. The
program then asks the user for a shapefile name.
Union boxes will be stored in this file, while
the left and right bank boxes, respectively, will
be stored in a file with the same name and the
characters _left and _right appended.
Finally, the user is asked for a threshold angle.
A value of 10 seems to work well.
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Example buffer boxes developed using Tool 3.
Lines 1 and 2 identical
Bank Line 2 (used to create buffer boxes)
Bank Line 1 (used only for bank length)
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Disclaimer Notice
The information on this site is subject to a
disclaimer notice. Thank you for visiting the
National Center for Earth Dynamics Web site and
reviewing our disclaimer notice. The Web site is
for informational purposes only and is not
intended to provide specific commercial, legal or
other professional advice. It is provided to you
solely for your own personal use and not for
purposes of distribution, public display, or any
other uses by you in any form or manner
whatsoever. The information on this Web site is
offered on an as is basis without warranty. The
readers of the information assume all risks from
using the information provided herein.

• This tool is provided free of charge. Use this
  tool at your own risk. In offering this tool, the
  following entities and persons do not accept any
  responsibility or liability for the tools use by
  third parties
• The National Center for Earth-surface Dynamics
• The universities and institutions associated
  with the National Center for Earth-surface
  dynamics and
• The authors of this tool.
• Users of this tool assume all responsibility for
  the tool results and application thereof. The
  readers of the information provided by the web
  site assume all risks from using the information
  provided herein. None of the above-mentioned
  entities and persons assume liability or
  responsibility for damage or injury to persons or
  property arising from any use of the tool,
  information, ideas or instruction contained in
  the information provided to you.

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Want more information?
For more information on this tool or the NCED
Stream Restoration Toolbox please contact the
author of this tool, J. Wesley Lauer, or the NCED
Stream Restoration Project Manager, Jeff Marr at
marrx003_at_umn.edu National Center for
Earth-surface Dynamics 2 3rd Ave SE, Minneapolis,
MN 55414 612.624.4606