Fish Passage GIS Analysis
Methodology and Output Data Specifications
BC Ministry of Environment
Prepared by
Simon Norris
Hillcrest Geographics
2870 Graham St
Victoria, BC
www.hillcrestgeo.ca
Craig Mount
BC Ministry of Environment
395 Waterfront Cres.
Victoria, BC
REVISION HISTORY
Date
Author
Description of Changes
May 28, 2008
May 29, 2008
June 3, 2008
Nov 4, 2008
March 1, 2009
Vers
ion
0.1
0.2
0.3
0.4
0.5
Simon Norris
Craig Mount
Richard Mark
Craig Mount
Craig Mount
March 5, 2009
0.6
Simon Norris
March 6, 2009
March 19, 2009
0.7
0.8
Craig Mount
Simon Norris
Initial draft.
1st comments
2nd comments
Requested revisions
Updated to reflect changes / improvements in
method
Updated output data specifications, minor text
changes
Incorporate comments from Richard Thompson
Added section 2.4
CONTENTS
1
Overview .............................................................................................................................. 2
2
Methodology ........................................................................................................................ 3
2.1
Build Stream Gradient segments ................................................................................... 3
2.2
Build Fish Bearing Stream Model .................................................................................. 4
2.3
Identify Road-Stream Crossings.................................................................................... 6
2.4
Prioritize Road-Stream Crossings ................................................................................. 6
3
Output Layer Data Specifications .......................................................................................... 8
3.1
Stream Gradient Segment Lines ................................................................................... 8
3.2
Road-Stream Crossing Points ....................................................................................... 9
3.3
Fish Habitat Lines....................................................................................................... 10
3.4
Fish Observation Event Table ..................................................................................... 11
3.5
Obstacle Event Table ................................................................................................. 12
3.6
Obstruction Event Table ............................................................................................. 13
3.7
Access to the Data ..................................................................................................... 13
Fish Passage GIS Analysis - BC Ministry of Environment
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1 OVERVIEW
To define the magnitude of Fish Passage issues in BC, a GIS analysis was undertaken to
estimate the total number of culverts, and classify all culverts as to whether they occur on
a fish bearing or non-fish bearing stream.
To generate this estimate, the GIS analysis modeled potential fish bearing stream reaches
by combining historical spatial data on known fish observations and natural obstructions
to fish passage (i.e : dams, waterfalls) with modeled stream gradient. In simple terms,
everything downstream of a known fish observation point was considered fish bearing.
Moving upstream from a known fish observation site, stream segments were considered
fish bearing until they encountered either an obstruction such as a waterfall or dam or a
sustained channel gradient of more than 25%.
The resulting network of modeled fish bearing and non-fish bearing streams was then
intersected with road data taken from the Digital Road Atlas (DRA) and Forest Tenure
Roads (FTEN) spatial coverages. Every intersection of a single line stream with a road
was considered a potential culvert location. Double line stream intersections were
excluded as these were assumed to typically be serviced by a span structure (such as a
bridge) which would not typically represent a barrier to upstream fish passage. While
many of the identified crossing sites will have a closed-bottom structure of some type in
place, some sites will have open bottom structures (such as pipe arches or wooden box
culverts). Again, properly designed and installed open bottom structures which maintain
channel width and retain the natural stream bed profile do not usually represent a barrier
to upstream fish passage. The use of these types of structures varies regionally and
temporally. The exact type of structure in place at any given crossing will not be known
until that site has had an assessment performed and that data is reflected in the spatial
database of crossings. Likewise, without detailed field inspections, we are not able to
classify these structures as being passable to fish or not.
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2 METHODOLOGY
2.1 BUILD STREAM GRADIENT SEGMENTS
It is generally accepted that channel gradient is a useful guide for identifying and
classifying stream reaches. Gradient has been widely used to identify areas that are too
steep for use by fish: typically > 20% grade. With that said, there are some species such
as Bull Trout and Dolly Varden / Cutthroat which can utilize reaches with a sustained
slope of up to 25%. (Forest Practices Code of BC, Fish Stream Identification Guidebook,
1995). To be conservative, we have used a channel gradient of 25% as the cut off
between fish bearing and non-fish bearing reaches. A stream reach is defined as a section
of stream which is relatively uniform in character, gradient, width, morphology and
discharge. Since we cannot easily derive information about morphology and discharge
from the GIS layers available, we must generate segments based strictly on channel
gradient. As such we will not call them reaches but simply ‘Stream Gradient Segments’.
As slope is not included in the current Corporate Watershed Base (CWB) stream network
data, stream gradient needed to be derived.
The process used to create stream gradient segments was:
1. Extract from LRDW:
o CWB Stream Network
(WHSE_BASEMAPPING.CWB_STREAM_NETWORKS_SP)
o TRIM Contour Lines
(WHSE_BASEMAPPING.TRIM_CONTOUR_LINES)
2. For watersheds with non-height of land boundaries (ie along USA, AB, YT, NWT
borders), the stream network may be broken. Ensure a contiguous stream network
for these watersheds by one of two methods. First, attempt to retain only the
streams upstream of the mouth of the major stream draining the watershed via
selection based on watershed code. For watersheds where this method does not
function or eliminates significant portions of the stream network, manually
remove non-contiguous streams and irrelevant streams from the network.
3. Remove side channels from the CWB Stream Network.
4. Split the remaining CWB Stream Network lines at each intersection with a TRIM
contour line, thereby creating a segmented stream line.
5. Identify stream segment break/end points as points where significant changes in
slope occur. A significant change in slope is defined as where the difference in the
lengths of two adjacent stream segments (the individual segments having been
Fish Passage GIS Analysis - BC Ministry of Environment
Page 3
broken at a contour line in step 4 above) is greater than the standard deviation of
the lengths of all the segments making up the given stream.
Difference in length of these two adjacent segments
(defined by contour crossings) is greater than the
standard deviation of all the segment lengths in that
stream and therefore a break is generated.
The gradient of the stream segment below the break
is 16% (fish bearing) while above the break it is
27% (non-fish bearing)
Figure 1. Example of stream segment breaking based on channel gradient.
6. Take original, non-side channel, CWB Stream network lines (not split by
contours), and split them at the break/end points identified in step 5. The resulting
stream segments are the ‘stream gradient segments’
7. Number the stream gradient segments sequentially, moving upstream.
8. Using a digital elevation model, determine the elevation at the end points of each
stream gradient segment.
9. Calculate slope of all stream gradient segments as:
(elevation at top of segment – elevation at bottom of segment) / length of segment
10. Insert side channel streams back into the Stream Gradient Segment network. Side
channels are present to ensure the network is complete and contiguous, but are not
broken into individual segments or given slope values.
2.2 BUILD FISH BEARING STREAM MODEL
Fish Bearing Streams were modeled using the derived Stream Gradient Segments,
Known Fish Observations, Obstruction Points, and Obstacle Points as inputs.
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The process for modeling fish bearing streams was:
1. Extract from the LRDW:
o
KNOWN FISH OBSERVATIONS in
(WHSE_FISH.FISS_FISH_OBSRVTN_PNT_SP)
To accommodate location imprecision in the Known Fish Observation
data, only retain Known Fish Observations that are either:
 < 50m from a Stream Gradient Reach network segment
 < 1000m from a Stream Gradient Reach network segment within a
waterbody
o
OBSTRUCTIONS in
(WHSE_BASEMAPPING.CWB_OBSTRUCTIONS_SP)
where OBSTRUCTION_TYPE = :
 DAM
 FALLS
o
OBSTACLESS in
(WHSE_FISH.FISS_OBSTACLES_PNT_SP)
where OBSTACLE_NAME = :
 DAM
 HYDRO DAM
 REGIONAL DISTRICT DAM
 IRRIGATION DISTRICT DAM
 FISHERIES MANAGEMENT DAM
 WATER MANAGEMENT STORAGE DAM
 WEIR
 FALLS (AND HEIGHT > 5M)
2. Using the network of Stream Gradient Segments, move upstream from the stream
mouth at the bottom of a watershed group and classify streams as fish bearing
until encountering one of the following:
o
o
a Stream Gradient Segment with slope greater than 25%
an Obstruction within 5m of a main channel segment on the network
(obstructions on side channels are not considered as the stream network is
too complex to model fish passage through multiple channels of the same
stream)
3. Classify as fish bearing all streams downstream of Known Fish Observations
retained in Step 1 above.
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2.3 IDENTIFY ROAD-STREAM CROSSINGS
Potential closed-bottom culverts are modeled as points where a road crosses a single line
stream (stream with width <20m). Double-line streams (>20m) are wide enough that
they will be spanned by bridges or other large open bottomed structures.
The process for generating road-stream crossings (modeled culverts) was as follows:
1. Extract from the LRDW:

Digital Road Atlas (DRA)
(WHSE_BASEMAPPING.DRA_DIGITAL_ROAD_ATLAS_LINE_SP)

Forest Tenure Roads (FTEN)
(WHSE_FOREST_TENURE.FTEN_ROAD_LINES)
2. From the Stream Gradient Segments, extract all single line streams
(EDGE_TYPE = 1000, 1050, 1100, 1150).
3. Generate points at all intersections of DRA roads and single line streams. Retain
the data from both line sources in the resulting points (including fish bearing
stream classification).
4. Generate points at all intersections of FTEN roads and single line streams. Retain
the data from both line sources in the resulting points (including fish bearing
stream classification).
5. Many roads are inventoried in both the DRA and FTEN datasets. To eliminate
double counting of equivalent roads, eliminate FTEN road-stream crossings <
10m from a DRA road-stream crossing.
6. Combine all DRA road-stream crossings with the remaining FTEN road stream
crossings into a single road-stream crossing dataset which retains data from all
line sources.
2.4 PRIORITIZE ROAD-STREAM CROSSINGS
As generated, the road-stream crossing dataset is a useful tool for quantifying the
magnitude of provincial and regional potential barriers to fish passage. However, with
further analysis it is possible to generate a rough index prioritizing crossings for
assessment and remediation. The index is an attempt to identify specific crossings where
the greatest amount of fish habitat will be gained for the least amount of restoration funds
invested.
To generate this index, the position of the road-stream crossings was referenced linearly
along the stream network. Given the relative position of all of the crossings on the stream
network, it is possible to use the attributes within the stream network (watershed code,
blue line key, downstream route measure) to determine what is upstream or downstream
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of any given crossing. Several functions were built to query the stream database to
calculate the following two key variables for each crossing point:


DOWNSTREAM CROSSINGS: The total number of crossings downstream of the
crossing. Assuming all crossings in the database are barriers to fish passage, this is
the number of crossings that would have to be remediated before fish could reach the
crossing under consideration.
UPSTREAM FISH HABITAT UNCROSSED: The total length of modeled fish
habitat upstream of the crossing (on all tributaries), but below any further crossings.
Assuming that fish can reach this crossing (all the downstream crossings are passable
to fish) and this crossing is a barrier to fish passage, this is how much additional fish
habitat would become available if the crossing is remediated.
While these variables are valuable independent of one another, they are most useful for
prioritizing assessments and remediation work when combined. A Habitat Gained Index
(HGI) is generated by dividing UPSTREAM FISH HABITAT UNCROSSED by
DOWNSTREAM CROSSINGS. This index provides a relative ‘bang for buck’
associated with repairing a given culvert. Culverts with a great deal of habitat upstream
and a small number of downstream culverts (requiring repair in order to realize this gain)
will have the highest values.
For example, if there are two adjacent valleys with similar road networks but only
enough time / money in the field season program to focus on one valley, the assessment
team will need to decide where best to focus their efforts. Before conducting
assessments, the team could look at a variety of variables to help decide which valley to
focus on first:
 Total number of culverts
 Total length of fish habitat
 Overall quality of fish habitat
 Average habitat gained index for all of the culverts in the valley
 Future access plans for the road networks (i.e. deactivation, upgrade, etc.)
By examining and comparing all of these factors for both of the road networks in
question, the assessment team should be able to decide where best to focus their efforts.
Similarly, once the assessments have been carried out, it will again be these types of
factors (along with projected repair cost for each structure) which will determine repair
and replacement priorities.
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3 OUTPUT LAYER DATA SPECIFICATIONS
3.1 STREAM GRADIENT SEGMENT LINES
LAYER NAME: StreamGradientSegments
LAYER DESCRIPTION: CWB stream routes broken into numbered segments at
significant changes in slope gradient.
FIELDS:
ATTRIBUTE NAME
GRADIENT SEGMENT
ID
BLUE LINE KEY
UPSTREAM ROUTE
MEASURE
DOWNSTREAM ROUTE
MEASURE
WATERSHED KEY
CWB WATERSHED
CODE
LOCAL WATERSHED
CODE
GRADIENT SEGMENT
NO
ELEVATION UPSTREAM
ELEVATION
DOWNSTREAM
GRADIENT
WATERSHED GROUP
CODE
DESCRIPTION
A unique numeric identifier used to link the arc to the database.
From Stream Network. Uniquely identifies a single flow line such
that a main channel and a secondary channel with the same
watershed code would have different blue line keys (the Fraser
River and all side channels have different blue line keys).
The distance along the route from the mouth of the route to the
upstream end of the feature.
The distance along the route from the mouth of the route to the
downstream end of the feature.
A key that identifies a stream system (for example the Fraser River
mainstem and all its side channels the same watershed key). There
is a 1:1 match between a watershed key and watershed code. The
watershed key will match the blue line key for the mainstem.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
The numbered position of the Gradient Segment along the stream
route. Gradient Segments are numbered sequentially moving
upstream from the mouth of the stream route.
The elevation at the upstream endpoint of the Stream Gradient
Segment.
The elevation at the downstream endpoint of the Stream Gradient
Segment.
The percentage slope of the Stream Gradient Segment.
(ELEVATION UPSTREAM - ELEVATION DOWNSTREAM) /
LENGTH METRES
The watershed group code the feature is contained within.
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3.2 ROAD-STREAM CROSSING POINTS
LAYER NAME: RoadStreamCrossings
LAYER DESCRIPTION: Points identifying intersections of single line CWB streams
and DRA/FTEN roads.
FIELDS:
ATTRIBUTE NAME
CROSSING ID
BLUE LINE KEY
ROUTE MEASURE
WATERSHED KEY
CWB WATERSHED
CODE
LOCAL WATERSHED
CODE
DIGITAL ROAD ATL
ROAD CLASS
MAP FEATURE ID
ROAD TENURE TYPE
FISH HABITAT
UPSTR FISH HABITAT
TOTAL
UPSTREAM CROSSINGS
UPSTR FISH HABITAT
UNCROSSED
DNSTR CROSSINGS
DNSTR CROSSING ID
WATERSHED GROUP
CODE
UTM ZONE
UTM EASTING
UTM NORTHING
DESCRIPTION
A unique numeric identifier used to link the point to the database.
From Stream Network. Uniquely identifies a single flow line such
that a main channel and a secondary channel with the same
watershed code would have different blue line keys (the Fraser
River and all side channels have different blue line keys).
The distance along the route from the mouth of the route to the feature.
A key that identifies a stream system (for example the Fraser River
mainstem and all its side channels the same watershed key). There
is a 1:1 match between a watershed key and watershed code. The
watershed key will match the blue line key for the mainstem.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
Unique ID linking to DRA database.
Road classification for DRA road crossings (ie highway, local,
unknown).
Unique ID linking to FTEN road database.
The road tenure classification for FTEN road crossings (FSR =
Forest Service Road, RP = Road Permit).
The FISH HABITAT value of the portion of stream on which the
crossing lies.
The total length of modeled fish habitat upstream of the crossing.
The total number of crossings upstream of the crossing.
The total length of modeled fish habitat upstream of the crossing
(on all tributaries), but below any further crossings.
The total number of crossings downstream of the crossing.
The CROSSING ID of the next crossing point downstream of the
crossing.
The watershed group code the feature is contained within.
The NAD83 Universal Mercator (UTM) Zone coordinate for the
downstream point of this obstacle.
The NAD83 Universal Mercator (UTM) Easting coordinate for the
downstream point of this obstacle.
The NAD83 Universal Mercator (UTM) Northing coordinate for the
downstream point of this obstacle.
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3.3 FISH HABITAT LINES
LAYER NAME: FishHabitatLines
LAYER DESCRIPTION: Portions of CWB stream routes modeled to be fish habitat
FIELDS:
ATTRIBUTE NAME
FISH HABITAT ID
BLUE LINE KEY
UPSTREAM ROUTE
MEASURE
DOWNSTREAM ROUTE
MEASURE
LENGTH METRE
WATERSHED KEY
CWB WATERSHED
CODE
LOCAL WATERSHED
CODE
FISH OBSERVATION
POINT ID
OBSTACLE POINT ID
OBSTRUCTION ID
GRADIENT SEGMENT
ID
FISH HABITAT
WATERSHED GROUP
CODE
DESCRIPTION
A unique numeric identifier used to link the arc to the database.
From Stream Network. Uniquely identifies a single flow line such
that a main channel and a secondary channel with the same
watershed code would have different blue line keys (the Fraser
River and all side channels have different blue line keys).
The distance along the route from the mouth of the route to the
upstream end of the feature.
The distance along the route from the mouth of the route to the
downstream end of the feature.
The length in metres of the linear object.
A key that identifies a stream system (for example the Fraser River
mainstem and all its side channels the same watershed key). There
is a 1:1 match between a watershed key and watershed code. The
watershed key will match the blue line key for the mainstem.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
The FISH OBSERVATION POINT ID of the most upstream
Fish Observation affecting the fish habitat classification.
The OBSTACLE POINT ID of the most downstream Obstacle
affecting the fish habitat classification.
The OBSTRUCTION ID of the most downstream Obstruction
affecting the fish habitat classification.
The GRADIENT SEG ID of the most downstream Stream
Gradient Segment with GRADIENT >25% affecting the fish
habitat classification.
The output from the fish habitat model. A value of "FISH
HABITAT - INFERRED" indicates that the portion of the stream
along the arc has no known impediments to fish passage. A value
of "FISH HABITAT - OBSERVED" indicates a portion. of
stream downstream of a fish observation point.
The watershed group code the feature is contained within.
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3.4 FISH OBSERVATION EVENT TABLE
TABLE NAME: FishObservations
TABLE DESCRIPTION: Fish Observations used for fish habitat model
FIELDS:
ATTRIBUTE NAME
FISH OBSERVATION
POINT ID
BLUE LINE KEY
ROUTE MEASURE
WATERSHED KEY
CWB WATERSHED CODE
LOCAL WATERSHED
CODE
WATERSHED GROUP
CODE
DESCRIPTION
Unique ID linking to source LRDW layer.
From Stream Network. Uniquely identifies a single flow line such
that a main channel and a secondary channel with the same
watershed code would have different blue line keys (the Fraser
River and all side channels have different blue line keys).
The distance along the route from the mouth of the route to the feature.
This distance is measured from the mouth of the containing route to the
downstream end of the feature.
A key that identifies a stream system (for example the Fraser River
mainstem and all its side channels the same watershed key). There
is a 1:1 match between a watershed key and watershed code. The
watershed key will match the blue line key for the mainstem.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
The watershed group code the feature is contained within.
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3.5 OBSTACLE EVENT TABLE
TABLE NAME: Obstacles
TABLE DESCRIPTION: Obstacles used for fish habitat model
FIELDS:
ATTRIBUTE NAME
OBSTACLE POINT ID
BLUE LINE KEY
DOWNSTREAM ROUTE
MEASURE
WATERSHED KEY
CWB WATERSHED CODE
LOCAL WATERSHED
CODE
WATERSHED GROUP
CODE
DESCRIPTION
Unique ID linking to source LRDW layer.
From Stream Network. Uniquely identifies a single flow line such
that a main channel and a secondary channel with the same
watershed code would have different blue line keys (the Fraser
River and all side channels have different blue line keys).
The distance along the route from the mouth of the route to the feature.
This distance is measured from the mouth of the containing route to the
downstream end of the feature.
A key that identifies a stream system (for example the Fraser River
mainstem and all its side channels the same watershed key). There
is a 1:1 match between a watershed key and watershed code. The
watershed key will match the blue line key for the mainstem.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located
within the province.
The watershed group code the feature is contained within.
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3.6 OBSTRUCTION EVENT TABLE
TABLE NAME: Obstructions
TABLE DESCRIPTION: Obstructions used for fish habitat model
FIELDS:
ATTRIBUTE NAME
OBSTRUCTION ID
BLUE LINE KEY
DESCRIPTION
Unique ID linking to source LRDW layer.
From Stream Network. Uniquely identifies a single flow line such
that a main channel and a secondary channel with the same
watershed code would have different blue line keys (the Fraser
River and all side channels have different blue line keys).
ROUTE MEASURE
The distance along the route from the mouth of the route to the feature.
This distance is measured from the mouth of the containing route to the
downstream end of the feature.
WATERSHED KEY
A key that identifies a stream system (for example the Fraser River
mainstem and all its side channels the same watershed key). There is a
1:1 match between a watershed key and watershed code. The watershed
key will match the blue line key for the mainstem.
CWB WATERSHED CODE
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located within the
province.
LOCAL WATERSHED
CODE
A 143 character code derived using a hierarchy coding scheme.
Approximately identifies where a particular stream is located within the
province.
WATERSHED GROUP
CODE
The watershed group code the feature is contained within.
3.7 ACCESS TO THE DATA
Data Steward: Craig Mount
Data Location: ftp site access
Data Format: ESRI Geodatabase
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