Stream channel reference sites : an illustrated guide to field technique

70 Pages·1994·4.6 MB·English

by  Harrelson, Cheryl C

Historic, Archive Document
Do not assume content reflects current
scientific knowledge, policies, or practices.

OA
Stream Channel
United Stat6S
(fiL&\
vaAsy Department of
Agriculture Reference
Sites
Forest Service
Rocky Mountain An Illustrated Guide to
Forest and Range
Experiment Station Field Technique ft cv
Fort Collins,
Colorado 80526
Cheryl C. Harrelson
General Technical
C. L. Rawlins
Report RM-245
John Potyondy
P.
m
T2£
Harrelson, Cheryl C; Rawlins, C. L.; Potyondy, John P. 1994. Stream channel reference sites: an illustrated guide to
field technique. Gen. Tech. Rep. RM-245. Fort Collins, CO: U.S. Department ofAgriculture, Forest Service, Rocky
Mountain Forest and Range Experiment Station. 61 p.
Abstract
This document is a guide to establishing permanent reference sites for
gatheringdata about the physical characteristics ofstreams and rivers. The
minimumprocedureconsistsofthefollowing:(1) selecta site,(2)mapthe site
and location, (3) measure the channel cross-section, (4) survey alongitudinal
profile ofthe channel,(5)measure streamflow,(6)measurebedmaterial, and
(7) permanently file the information with the Vigil network. The document
includes basic surveying techniques, provides guidelines for identifying
bankfull indicators and measuring other important stream characteristics.
The object is to establish the baseline ofexisting physical conditions for the
stream channel. With this foundation, changes in the character ofstreams
can be quantified for monitoring purposes or to support other management
decisions.
Keywords: reference sites, stream channel monitoring, measurement tech-
niques.
Prepared in support of the National Stream Systems Technology Center
mission to enable land managers to "secure favorable conditions of water
flows" from our National Forests.
USDA Forest Service April 1994
General Technical Report RM-245
Stream Channel Reference
Sites:
An Illustrated Guide to Field Technique
Cheryl C. Harrelson, Hydrologist
Bridger-Teton National Forest
2
C. L. Rawlins, Hydrology Technician
Lincoln National Forest
3
John P. Potyondy, Hydrologist
Rocky Mountain Forest and Range Experiment Station
' Cheryl C. Harrelson was a hydrologist on the Lincoln andBridger-Teton NationalForests. She has a B.S. in Watershed Science from Colorado
State University.
2 C. L. Rawlins was a hydrology technician on the Bridger-Teton National Forest andreceived the USDA Forest Service's National Primitive Skills
Awardin 1989. He has B.S. and M.S. degrees from Utah State and was a StegnerFellow at Stanford University.
3 John P. Potyondy is a Hydrologist with the Rocky Mountain Forest and Range Experiment Station's Stream Systems Technology Center. He
has B.S. and M.S. degrees from the University ofMinnesota in Forestry. He has served as a Hydrologist at the Boise and Wasatch-Cache
National Forests and at the Intermountain Region Regional Office.
Contents
1. Introduction 1
.
2. Selecting a Site 3
.
3. General Location Map 8
4. Drawing a Site Map 10
5. Surveying Basics 13
6. Measuring Channel Cross-Section 26
7. Floodplain and Bankfull Indicators 33
8. Longitudinal Profile Measurement 37
9. Installing a Staff Gage 42
10. Measuring Discharge 44
11. Bed and Bank Material Characterization 49
12. Permanent Files 53
References 55
Appendix A. Equipment List 56
Appendix B. Sample Vigil Site Record 57
Stream Channel Reference Sites:
An Illustrated Guide to Field Technique
Cheryl C. Harrelson, C.L. Rawlins, and John P. Potyondy
Introduction
1.
This document is a guide to establishing per- cross-section, a longitudinal profile, a pebble
manent reference sites for gathering data about count, and a discharge measurement. The object
streams and rivers. It presents techniques from is to find the baseline ofexisting physical condi-
a variety of published sources in a single, com- tions for the stream channel. With this founda-
pact field manual. Use of these techniques will tion of technically correct and comparable data,
provide the sound, factual information needed to we can track changes in the character of the
quantify the existing physical character of stream.
stream channels. The ability to accurately make
and replicate stream channel measurements
over a period of years and through changes in POTENTIAL USES OF DATA
personnel is vital. To ensure the applicability of
data collected with this manual, we consulted Permanent reference site data is useful in
hydrologists in the Forest Service, U. S. Geologi- many different contexts, supporting both local
cal Survey, and private practice. We aimed to management decisions and broad research ef-
identify a set ofbasic procedures that will yield forts. The baseline established is a foundation
quality data without a high degree ofspecializa- for a broad range ofphysical, chemical, and bio-
tion and at relatively low cost. logical monitoringtechniques. Potential uses for
This manual is for entry-level hydrologists, reference station data include
biologists, and others directly responsible for • monitoring trends in fluvial and geo-
managing streams andriparian areas. Thefocus
morphic condition over time;
is practical and specific. Field datawas collected
at one location to demonstrate these procedures • quantifying environmental impact;
and to serve as a consistent example throughout • assessing stream and watershed re-
the manual. sponse to management;
• providing channel and flow facts for
water allocation;
OBJECTIVES
• supporting resource inventories (habi-
tat, water quality, vegetation);
Natural systems have rhythms that can be
difficult to describe. Some, like the seasonal rise • tracking cumulative effects for entire
and fall of water in a stream, can be measured drainage areas;
simply. Others, like the lateral migration of • allowing valid comparisons based on
channels across a floodplain, or changes in re- stream type; and
gional climate, may take decades or even life-
times to occur. To accurately record such • contributing to regional, national, and
changes takes an extension of human memory international databases.
throughrepeated measurement and scientificre- The techniques in this manual yield a basic,
cords. minimum set ofphysical data on streams. Users
Placingapermanent, benchmarkedreference needto expand the amount ofdata collectedto fit
site is the first step in this long-term effort. Cor- their specific needs. For example, ifthe object is
rectly done, it will support further work over to assess changes at one site over time, then
time. The other elements are a monumented collect the basic data set at regular intervals. If
1
the object is to compare pristine to disturbed shows you the technically correct way to make
watersheds, or to assessthe response ofdifferent those measurements.
streams to management, then select several The minimum procedureconsistsofthefollowing:
reaches ofsimilar type.
A detailed study of channel response might 1. Select a site.
survey multiple cross-sections to map riffles, 2. Map the site and location.
pools, and meander bends. A study focused on
habitat might collect further data on aquatic 3. Measure the channel cross section.
insects, plant communities, or groundwater. Re- 4. Survey a longitudinal profile ofthe
gardless of the study's breadth or complexity, an channel.
accurate physical description ofthe stream is es-
sential, along with consideration ofstatistical de- 5. Measure stream flow.
signThinisthgeupildaenncionvgerosfatnhyedmaitanicomlluemctinoeneedffeodrt.to 6. Measure bed material.
accurately characterize stream channels and 7. Permanently file the information.
2
—
Selecting a Site
2.
Universal physical laws govern streams, yet and meters to the nearest stream. Planningpro-
every stream passes in a unique way through its videsgreater assurance ofsuccess. Theplanning
landscape. Gravity and water are constants, so phase consists mostly ofasking questions:
ealvlers,trdeifafmesretnecnedstionwlaorcdataiosninaglnedidpehaylsifcoarlm;cohnodwi-- •What do we want to know about this
tions create the range of forms we see. Each stream or drainage?
stream balances erosion, transport, and deposi-
tion in the context ofits climate and landscape. • What variations (geology, elevation,
We may classify stream channels in terms of land use) exist in the area?
eight majorvariables: width, depth, velocity, dis-
charge, slope, roughness ofbed andbank materi- • How can we set up the most useful com-
als, sediment load, and sediment size (Leopold et parisons with the fewest sites?
—
acla.se1—96a4r)e.notNartaunrdaolmsiynsttheeimrsvarsitarteioanm,sbuitn ttehnids • How can this site contribute to existing
to cluster around the mostlikely combinations of or planned efforts?
variables based on physical and chemical laws
rather than act randomly in their variation. • How much can be accomplished with
This tendency to seek a probable balance offac- present resources?
tors lends itselfto classification. Before taking to the field, take to the files.
When any of the factors controlling stream Find out what has been done inyour area. Often
classification change, the others will adjust benchmarks, gages, or reference sites already
along with it toward a new, balanced state. Be- exist. Other agencies such as the U.S. Geological
cause change is continuous, so is the process of Survey may have studies that can be expanded
adjustment. In streams the strongest physical
or extended for your purposes.
medium for adjustment is the flow of water. In Document what has been done. Contact per-
adjusting, the stream will show measurable sonsworkinginyour area. Valuable studiesmay
change along the continuum determined by this have been done by a local irrigation district or as
flowA(Rosgen 1994). part ofa fisheries project. Aday spent with files
steep streamthat enters agentlevalleywill or in a library, or contacting others, may reward
show a continuous change in several parameters you with useful information.
from one state (cascades and stepped pools) to Review sources on regional climate, geology,
another (meanders, pools, and riffles). Sharp land types, vegetation, historic land uses, and
boundaries, such as Yosemite Falls, tend to be forest plan guidelines. This overview can help
the ex—ception rather than the rule. A distinct you select good sites based on differences in wa-
event a tree falling into the stream, a landslide tershed character. For example, if there are
across the channel, or construction of a road three major geologic types on your forest, you
may drive the adjustment process in anew direc- may want to locate a station within each of the
tion. types. Sites might be located to compare stream
Understanding the process of change takes channel responses to management such as a
both accurate measurement and scientific inter- stream in a roadless drainage against a similar
pretation. The permanent reference site estab- one in a drainage withroads and timber harvest.
lishes baseline conditions to provide an accurate Planning guides your choice ofsite and helps
basis for measuring change.
to avoid mistakes like establishing a reference
site in July on a stream exactly where a fish
habitat construction project is planned for late
PLANNING
August.
Planning should focus on efficient use ofper-
The process of deciding where to locate your sonnel, vehicles, and funds. Coordinating the
reference site needs careful thought. Avoid the establishment offield sites with other field work
temptation to takeyourlevel, rod,waders, tapes, can lower costs.
3
STREAM CLASSIFICATION This produces 41 major stream types. The
above oversimplifies the Rosgen system, which
Stream classification provides a way to look includes additional parameters (see table 1, page
at stream channels, lettingyou group those that 6). For more complete information about the
are similar oridentifyfeaturesthatare different. classification and associated inventory proce-
Since we expect streams ofsimilar type to act in dures, see Rosgen (1994). Ultimately, stream
similarways, classification offers a powerful tool classificationhelpstodistinguishvariations dueto
for selecting streams for comparison. stream type from variations in the state or condi-
Ofthe various useful classifications that exist, tion ofsites.
the system developedby D.L. Rosgen is most com- Stream variables adjust continuously both
monly used by USDAForest Service hydrologists. through time and along the channel. Usually, one
Rosgen (1994) intends his classification to perfect stream type does not yield at a certain
allow point to the next perfect type; the changes are
continuous rather than sharply bounded. Recall-
• prediction of a river's behavior from its
ing the stream continuum concept during classifi-
appearance;
cation helps resolve problems that arise when one
• comparison of site-specific data from a parameteris outside the range for the stream type
impliedby the majority ofparameters considered.
given reach to data from other reaches
of similar character; and The decision that must be made at this point
is whether to undertake a comprehensive inven-
• a consistent and reproducible system of tory or to select a few representative watersheds.
technical communication for river stud- This depends on the concerns driving the data
ies across a range ofdisciplines. collection process. Long-term processes, such as
a Forest Plan revision, an interagency monitor-
Rosgen's classification scheme initially sorts ing effort, or an ecosystem management plan,
streams into the major, broad stream types(A-G) require a deliberate approach to site selection
at a landscape level, as showninfigure 1. Atthis and may include work over several years.
level, the system classifies streams from head- If, on the other hand, an immediate demand
waters to lowlands with stream type: forinformationto support a courtbriefdrives the
—
A headwater process, the choice of sites and time may be
B — intermediate strictly limited. Short-term measurement, if
— done to the proper standards, creates a potential
C & E meandering
—
D
braided
—
F entrenched
—
G
gully
The Rosgen system breaks stream types into
subtypes based on slope ranges (fig. 2) and domi-
nant channel material particle sizes (fig. 3).
Subtypes are assignednumbers correspondingto
the median particle diameter ofchannel materi-
als:
1 = bedrock
2 = boulder
3 = cobble
4 = gravel
5 = sand
Figure 1. -Stream types in a mountain landscape (adapted
6 = silt/clay from Rosgen 1964). CourtesyofDavid Rosgen,Wildland
Hydrology Consultants.
4