Habitat Data
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ABSTRACT

    The Oregon Department of Fish & Wildlife has been actively acquiring stream habitat inventory information for the purpose of habitat assessment since 1990.  This information is collected during the summer months by stream survey crews using methods described in Moore et al. (1997).  The field data focuses on channel and valley morphology (stream and reach data), riparian characteristics and condition (reach data), and instream habitat (habitat unit data).
    The survey data is compiled into a comprehensive database that is used in fish management and planning activities.  The data are dynamically segmented in a geographic information system (ArcInfo) onto a 1:100,000 scale digitized stream layer to display habitat features and combinations of habitat features relative to location of streams, reaches, and habitat units in the watershed.  The 1:100,000 scale digitized stream layer was originally digitized by the USGS in their PNW River Routes Project.  It was later modified by ODFW’s GIS Division to include a complete stream routing system.  This modified route system provides the basis for our reach and habitat coverages.
    The stream habitat distribution coverages provide a means for accessing stream data in an electronic medium.  It increases the ease of data dispersal and allows for the assessment of basin wide characteristics.  It also allows for stream and basin analysis to occur from a spatial scale and perspective.

LIMITATIONS OF AQUATIC INVENTORIES PROJECT DATA

    The Aquatic Inventories Project (AIP) survey data is compiled in two datasets (reach and habitat unit).  These datasets are collected using the methodology as described by Moore et al. (1997).  The current methods are available at the following web page:
http://osu.orst.edu/Dept/ODFW/freshwater/inventory/availinfo.html
These survey methods allow for the collection of hierarchically organized information continuously from the stream mouth to headwaters.  The purpose of this survey method is to inventory the applicable aspects of the riparian environment as they relate to fish habitat.  The data is meant to be used as a means of determining habitat distribution and quality.  It has been used successfully in the preparation of restoration plans, assessment of fish production and survival potential, and the determination of management priorities.
    It is important to remember that the data contained in AIP datasets reflect the condition of the stream at the time of the survey.  Streams are dynamic systems that change with every high or low flow event.  Substrate and woody debris move through the system, trees fall into the stream causing changes in flow and habitat type.  Pools are formed and filled in annually.  It is the purpose of the survey to document the condition of the stream at the time of the survey.  This data may be used later for comparison and management planning work.
    The reach dataset generalizes the habitat units that are surveyed by the crew.  It provides an overview of the conditions within the reach or section of stream.  A reach is defined by the field survey crew at the time of the survey.  It may simply be the distance surveyed.  More frequently, reaches are defined as: stream segments between named tributaries, changes in valley and channel form, major changes in vegetation type, or changes in land use or ownership (Moore et al, 1998 p. 5).  It should be a reference point for later comparative work or for the analysis of stream conditions.
    The habitat dataset includes all of the unit data for the entire survey.  It is within this dataset that the most noticeable annual change will occur.  There are two basic types of habitat units: channel geomorphic units and special case units.  Channel geomorphic units are relatively homogeneous lengths of the stream that are classified by channel bed form, flow characteristics, and water surface slope.  Geomorphic habitat units include pools, riffles and glides.  Special case units describe situations where, because of stream flow level or a road crossing, the usual channel geomorphic unit types do not occur.  Special case units include dry or partly dry channels, and culverts (Moore et al, 1998 pp. 12-13).  There will be changes in the distribution, size and location of habitat types annually.  This dataset is not intended to be a map of the absolute distribution of habitat types.  Rather, it indicates the condition of the stream at the time of the survey.

USING QUERIES IN ARC VIEW

    Queries are a useful tool in ArcView for displaying specific habitat variables or criteria.  There are appropriate ways of querying both the habitat unit and reach datasets to answer a variety of management and research questions.  Strengths and weaknesses are inherent in either analysis of the reach or habitat unit databases.   The methods for using the datasets are essentially the same.  Either simple queries of the data can be performed (at the reach or habitat unit scale), or the data can be reorganized to answer specific questions.  The most important steps are to 1) determine the objectives for the queries and 2) define the variables and criteria necessary to meet the objectives.

Simple Data Queries of Reaches or Habitat Units

Simple Reach Queries:

    As previously mentioned, reaches are portions of stream defined because of similarities in geomorphology, hydrology, land use, substrate composition, or riparian vegetation.  Reach data summarizes the habitat unit data for the reach and includes descriptors of channel type, pool character and amount, large wood debris, substrate, bank condition, and riparian characteristics.  Analysis of the reach data has proven useful in the identification of restoration sites, monitoring of riparian conditions and estimation of fish population abundance.
    Reach data encompasses a wide variety of variables, therefore, the diversity of possible queries is great.  A sample query was performed on the reach coverage for the Tillamook River watershed on the north Oregon coast.  We were interested in identifying areas that met coho salmon life history requirements.  The three tiered query of the Tillamook River watershed reach coverage was performed based on three criteria:
    1.  pool habitat > 30% habitat area
    2.  gravel in spawning habitat comprised >30% of the substrate area
    3.  the number of pools greater than 1m in depth > 2 per km
The query results showed limited reaches within this watershed that could be characterized as containing good habitat for all coho life stages.  Of the 53 reaches available, 5 were chosen that met the query criteria (Map 1).

Map 1

This simple query of the existing reach dataset allowed us to identify those areas within the Tillamook watershed that had habitat conditions suitable for coho salmon.  Similar queries could be performed for any species of salmon or trout. 

Simple Habitat Unit Queries

    Habitat units are the structural building blocks of a stream.  As previously mentioned, there are two basic types of habitat units: channel geomorphic units and special case units.  Geomorphic habitat units include pools, riffles and glides.  Special case units describe situations where, because of stream flow level or a road crossing, the usual channel geomorphic unit types do not occur.  Special case units include dry or partly dry channels, and culverts (Moore et al, 1997 pp. 12-13).  When properly analyzed, habitat units provide a good picture of stream habitat.
    For GIS analysis, we performed two sets of queries in ArcView 3.1 that delineated habitat important for all life stages of coho salmon.  The first set of queries was used to identify rearing habitat while the second was designed to locate appropriate spawning habitat in the Tillamook River watershed.  The query for rearing habitat was more involved than the one for spawning habitat.  Rearing habitat was identified by three separate sets of information.  These were:
  1. all pool habitat
  2. deep pools (> 1.0 meter in depth)
  3. slow water habitats such as alcoves, backwaters and beaver dam pools

The query used to identify spawning habitat was more simple.  We looked for:
  1.  riffle habitat with at least 30% gravel substrate and less than 15% fine sediments.

    When all of the queries for spawning and rearing habitat were put together, a visual assessment of the distributions showed that spawning and rearing habitat for coho was located throughout the basin, but not all streams possessed both spawning and rearing habitat (Map 2).  This is an important distinction to make in the assessment of population viability and opens the door to a variety of other factors that would be useful in the determination of habitat health in the area.

Map 2

Reorganizing Data for Analysis

    Reorganizing the reach and habitat level data allows us to answer specific research questions.  This is accomplished by querying the unit level data for variables that we are interested in.  Once this has been accomplished, we can generate reaches based on the habitat unit query results.  Reaches contain summarized information from the unit level data and can provide an avenue for the comparison of different variables over an entire stream.  In this way, queries of the habitat data can drive the creation of reaches.
    An example of this analysis was completed for Bewley Creek in the Tillamook River watershed.  We  followed the query steps as described in the "Simple Habitat Unit Queries" section.  However, instead of finishing our analysis, we then use the results to redefine reaches.

    We reclassified the reaches on Bewley Creek based on the distribution of coho habitat.  Three reaches were identified in the original survey based on geomorphic criteria.  We started the reclassification process by using the queries identified in the "Simple Habitat Unit Queries section".  When these queries were completed they were used in concert with land ownership and seven reaches were visually identified (Map 3).  Reaches 1 and 2 showed potential differences in pool composition and were identified as rearing reaches.  Reaches 3 and 5 stood out as potentially important spawning areas due to their concentration of low silt riffles.  Reaches 4 and 6 appeared to have many deep pools.  Reach 7 was differentiated because of an apparent decrease in deep pool habitat.  We were then able to resummarize the unit level information into these seven new reaches.

Map 3

    The newly generated summary statistics for Bewley Creek corroborate the visual assessment of habitat differentiation (Table 1).  Reaches 1 and 2 were separated by a land use change from light grazing to young timber.  Both reaches were pool dominated, however, reach 1 contained more pool area as well as higher numbers of deep pools per kilometer than reach 2.  Reaches 3 and 5 have high contents of riffle gravel with lower amounts of fine sediments than all other reaches.  The number of deep pools are the lowest for reaches 3 and 5.  Reach 4 is dominated by pool habitats and has a high number of deep pools per kilometer.  Reaches 6 and 7 are also dominated by pools and both have high numbers of slow water habitats for rearing.  The gradient in reach 7 is higher than in the other reaches which is characteristic of the headwaters of a stream.  The original survey subdivided Bewley Creek into 3 geomorphic reaches.  Restratification by biological criteria and geographic technique identified 7 reaches as high quality adult spawning or juvenile rearing areas and displayed their location in relation to land use patterns. 

TABLE 1

BEWLEY CREEK REACH SUMMARY TABLE (POST REACH RECLASSIFICATION)

Stream	Reach	Length	2nd Channel Length	Gradient	Bank Erosion	Pools % area	Deep Pools/km**	Slow Water % area ***	Riffles % area	Riffle Fines %	Riffle Gravel %
Bewley	1	1 635	5	0.3	71.0	35.6	18.3	0.0	12.3	59.0	28.0
	2	3 442	40	0.3	36.0	24.6	5.5	0.1	27.1	40.0	36.0
	3	665	0	0.3	22.6	21.1	0.0	0.0	17.2	10.0	40.0
	4	961	14	0.3	3.2	66.1	10.3	2.2	12.5	43.0	54.0
	5	1 090	62	0.9	0.0	45.8	1.7	2.8	35.5	20.0	50.0
	6	1 262	79	0.9	0.0	75.8	6.0	28.5	22.9	36.0	40.0
	7	1 872	145	2.2	1.9	55.4	4.0	15.0	38.7	40.0	56.0

* Wood pieces used > 0.15m dbh.
** Deep pools defined as pools with depth greater than 1.0 meter.
*** Slow water habitats include dammed and backwater areas, alcoves and beaver pools.