Section 6 Physical Habitat Characterization— Non-wadeable Rivers by Philip R. Kaufmann In the broad sense, physical habitat in ecology that are likely applicable in rivers as rivers includes all those physical attributes that well. They include: influence or provide sustenance to river or- • Channel Dimensions ganisms. Physical habitat varies naturally, as do biological characteristics; thus expectations • Channel Gradient differ even in the absence of anthropogenic disturbance. Within a given physiographic- • Channel Substrate Size and Type climatic region, river drainage area and chan- • Habitat Complexity and Cover nel gradient are likely to be strong natural determinants of many aspects of river habitat, • Riparian Vegetation Cover and Struc- because of their influence on discharge, flood ture stage, and stream power (the product of dis- charge times gradient). Summarizing the habi- • Anthropogenic Alterations tat results of a workshop conducted by EMAP • Channel-Riparian Interaction on stream monitoring design, Kaufmann (1993) identified seven general physical habi- All of these attributes may be directly or tat attributes important in influencing stream indirectly altered by anthropogenic activities. Nevertheless, their expected values tend to 1U.S. EPA, National Health and Environmental Effects Re- vary systematically with river size (drainage search Laboratory, Western Ecology Division, 200 SW 35th St., Corvallis, OR 97333. area) and overall gradient (as measured from 6-1 topographic maps). The relationships of spe- scales the sampling reach length and resolu- cific physical habitat measurements described tion in proportion to stream size. It also al- in this EMAP-SW field manual to these seven lows statistical and series analyses of the data attributes are discussed by Kaufmann (1993). that are not possible under other designs. We Aquatic macrophytes, riparian vegetation, and strive to make the protocol objective and re- large woody debris are included in this and peatable by using easily learned, repeatable other physical habitat assessments because of measures of physical habitat in place of esti- their role in modifying habitat structure and mation techniques wherever possible. Where light inputs, even though they are actually bio- estimation is employed, we direct the sam- logical measures. The field physical habitat pling crew to estimate attributes that are oth- measurements from this field habitat charac- erwise measurable, rather than estimating the terization are used in the context of water quality or importance of the attribute to biota chemistry, temperature, and other data sources or its importance as an indicator of distur- (e.g., remote sensing of basin land use and bance. We have included the more traditional land cover). The combined data analyses will visual classification of channel unit scale habi- more comprehensively describe additional tat types because they have been useful in habitat attributes and larger scales of physical past studies and enhance comparability with habitat or human disturbance than are evalu- other work. ated by the field assessment alone. The time commitment to gain repeatabil- This protocol is intended for evaluating ity and precision is greater than that required physical habitat in non-wadeable streams and for more qualitative methods. In our field tri- rivers. Kaufmann and Robison (1998) de- als, two people typically complete the speci- scribe other methods for use in smaller, wade- fied channel, riparian, and discharge measure- able streams. Like the methods for wadeable ments in about three hours of field time. streams, these methods are most efficient dur- However, the time required can vary consid- ing low flow conditions and when leaves are erably with channel characteristics, flow con- on terrestrial vegetation, but may be applied ditions, and the location of boat launching during other seasons and higher flows except areas. as limited by safety considerations. It is de- The protocol defines the length of each signed for monitoring applications where ro- sampling reach proportional to river wetted bust, quantitative descriptions of reach-scale width and then systematically places measure- habitat are desired, but time is limited. ments to statistically represent the entire reach. Like the wadeable streams protocol Stream thalweg depth measurements, habitat (Kaufmann and Robison 1998) this habitat classification, and mid-channel substrate ob- characterization approach employs a random- servations are made at very tightly spaced in- ized, systematic spatial sampling design to tervals; whereas channel "littoral" and ripar- minimize bias in the placement and position- ian stations for measuring or observing ing of measurements. Measures are taken over substrate, fish cover, large woody debris, bank defined channel areas and these sampling ar- characteristics and riparian vegetation struc- eas or points are placed systematically at spac- ture are spaced further apart. The tightly ings that are proportional to baseflow chan- spaced depth measures allow calculation of nel width. This systematic sampling design indices of channel structural complexity, ob- 6-2 jective classification of channel units such as Mid-channel habitat measurements and pools, and quantification of residual pool observations are recorded on multiple pages depth, pool volume, and total stream volume. of the Thalweg Profile Form (Figure 6-3). Instructions for these mid-channel procedures 6.1 Components of the are given in section 6.5. Measurements made Field Habitat while anchored or tied up to the 11 littoral/ riparian plot stations ("transects") are recorded Assessment on 11 copies of the two sided Channel/Ri- parian Transect Form (Figures 6-4 and 6-5). Field data collection for the physical Instructions for these transect or littoral/ripar- habitat assessment is accomplished in a single ian assessment activities are discussed in sub- float down each river sample reach. Depend- section 6.6. ing on the survey region, river sample reach lengths are defined as either 40 or 100 times 6.2 Habitat Sampling the wetted width in the vicinity of the point of entry (Figure 6-1). In addition to physical Locations On The Study habitat assessment, the 2-person habitat team of the field crew collects chemical, Reach macroinvertebrate, and periphyton samples (if Measurements are made at two scales of applicable). They may also recon the chan- resolution along the mid-channel length of the nel if they precede the electrofishing boat down reach; the results are later aggregated and ex- the river. To characterize mid-channel habitat pressed for the entire reach, a third level of (Table 6-1), they measure a longitudinal thal- resolution (Figure 6-1). We want to assess weg (or mid-channel) depth profile, tally habitat and other river indices over river reach snags, classify channel habitat types, charac- lengths that are long enough to incorporate terize mid-channel substrate, and locate the the habitat variability due to river meander- 11 systematic transect locations for littoral/ri- ing and pool-riffle structure. To accommodate parian sampling and other habitat observations habitat variability in a way that adjusts for (Figures 6-1 and 6-2). At each of the 11 varying sizes of rivers, EMAP protocols marked reach transect locations (A-K), they specify sample reach lengths that are a mul- measure channel wetted width, bankfull chan- tiple of their average wetted width (40 or 100 nel dimensions, incision, channel constraint, Channel-Widths). Water velocity, habitat bearing and gradient; then assess near-shore, complexity, fish abundance, and species rich- shoreline, and riparian physical habitat char- ness may also affect capture efficiency and acteristics by measuring or observing littoral consequently the required sample reach depths, riparian canopy cover, substrate, large length. In the Oregon river pilot, it was found woody debris, fish cover, bank characteris- that 85 channel widths is adequate for Oregon tics, riparian vegetation, and evidence of hu- rivers (Hughes et al. In Review). In the Mid- man activities (Table 6-1). They also collect Atlantic region, river reaches of 40 channel benthic macroinvertebrates (Section 9), take widths long were used in order to make this benthic algal samples (if applicable), and aspect of field methods consistent between measure conductivity and water temperature wadeable and non-wadeable streams. For this using procedures described in section 5. field manual, we discuss the methods used to 6-3 Figure 6-1. River reach sample layout. 6-4 Table 6-1. Components of River Physical Habitat Protocol. 1. Thalweg Profile: At 10 equally spaced intervals between each of 11 channel cross-sections (100 along entire reach): * Classify habitat type, record presence of backwater and off-channel habitats. (10 between cross sections, 100 total) * Determine dominant substrate visually or using sounding rod. (10 between cross-sections, 100 total) At 20 equally spaced intervals (for 100 ChW reach) or 10 equally spaced intervals (for 40 ChW reach) between each of 11 channel cross-sections: * Tally mid-channel snags - 10 (or 20) between cross-sections, 100(or 200) total. * Measure thalweg (maximum) depth using Sonar or rod - 10 (or 20) between cross-sections, 100(or 200) total. 2. Littoral/Riparian Cross-Sections: @ 11 stops ("transects") at equal intervals along reach length: Measure/estimate from one chosen bank on 11 channel cross-sections: * Gradient (clinometer or Abney level) between