HomeMy WebLinkAbout6 Bank Stabilization and GeomorphitologyLandscape Information for
Streambank Stabilization Projects
John Gleason , Landscape Architect
City of Austin -Watershed Protection and Development Review Department
February 12 , 2002
Landscape Design of Streambank Stabilization Projects
Healthy, vigorous landscapes will help to ensure long-term survival of a streambank erosion control project. As with any
landscape design, success depends on a thorough analysis of the site to determine the opportunities and constraints offered by the
sites ' hydrolo gy , soils , and light conditions. The following information discusses these and other factors that are critical to the
success of streambank stabilization projects .
• Plant Selection : Using plants to help stabilize streambanks is risky business . The potential exists for the vegetation to be
swept downstream during severe storms , especially during the plant establishment phase . Since these plants will typically not
receive any extra care after the establishment period, they need to be adapted to the unique environment in which they are
placed . Thus, more than in typical (ornamental) landscape projects, there is a greater need for the designer to choose plant
species appropriate to site conditions . Ideally, the plants will have a strong root system and an iron constitution.
• Moisture : Availabil ity of moisture is a critical issue in plant survivability . See information below on 'Hydrozones '.
• Season of Installation : Your choice of plant material in a specific design must be aligned with the timing of installation .
Some plants are available only during certain seasons . Li ve cuttings , such as brush layers or fascines , must be made only
during the cool season, when the parent material is full y dormant. The timing of the planting may affect plant availab ility.
• Sunli ght and Shade : The shade cast by over-story plants on planting sites has a marked influence on the species composition
and veg etative production of plants that grow there . Competition for light between plants is a major factor in plant growth
just as is competition for other essentials such as moisture and nutrients . As shade increases in density , non-shade tolerant
specie s are either replaced by shade tolerant species , or the y die out and the ground is left barren.
• Soil : The d epth , texture, and presence or absence of rock, organic matter , and weed seed are all issues that should be of
concern to the designer. Soil depth will restrict root development. Roots will not penetrate be yond restrictive layers such as
bedro ck or hardpan whi ch water seldom penetrates .
• Slope : Ra inwater will run off a steep slope quickly, minimizing infiltration and the plants ' access to moisture .
• Plant Avail ability : N ative grasses and other riparian plants are becoming ly increas ing ly available in the nursery trade .
Howe ver, availability will fl uctuate based on season and current demand for certain specie s.
• Plant Success ion : The plant community that is planted when the projec t is installed is likely to evolve over time . The goal of
the designer is to protect the soil in the short-term with adapted plants , and allow Nature to determine species composition
over the long-term .
Plant List -Explanation of Categories
The followin g matrix li sts plants that could be used on streambank stabilization projects. The columns in th e matrix present
info rmation ab out indi vidu al species . Ho wever, plants do not al ways fall nea tl y into di sc rete cate gorie s, so occa sionally
compromis es ha ve been made . Information pertaining to th e character of a plant, the environmental zones in which it will grow,
and additional comments will help the de signer us e th e plant succe ssfull y. While man y o f the plants will gro w in areas other than
central Texa s, information p ertaining to the plants (particularl y th e zon es in which the y will grow ) was written for the local
regi on .
Plant
Bo tan ica l Na me
C ommon Name
Fi gure 1. -Plant Li st: Column Headings
Character Zones
Pl ant
Type /Use
Ht ./ Ro ot Hard Hyd ro S un /
Wid e system ines s zon e S hade
Comments
Note s on in sta llation , desi gn feature s,
tole ra nce s, preference s, etc .
Plant Column
• Botanical Name : A Latin name using two or more words. The first word places the plant into a broad category called the
Genus; the second is specific to a plant and is called the Species name . Additional words are sometimes used to identify
unique hybrids, cultivars, selections, etc.
• Common Name: A popular name applied to the species . Often, several common names are given to the same plant, with
individual use based on regional or personal preference. Botanical names are always more accurate than common names.
Character Column
• Plant Type/Use: Plants are warm-season perennials unless noted otherwise. Perennial means that it maintains the same root
system from year to year. Deciduous means that the plant loses it's' leaves during the cold season. With some plants, there is
a fine line between classifying it as a shrub or a tree . The final determination is based on the plant size and form.
• Height/Width: The sizes given are for mature plants growing in good conditions. Specimens growing in ideal conditions
may grow much larger. Poor growing conditions will place the plant in stress and often cause stunted growth. The height
given for the clump grasses presents them at their tallest, when flowers and/or seedheads are produced, which are sometimes
held high above the foliage .
• Root System: Root growth and development are primarily affected by two factors :
1. The growth characteristics of the species themselves
2. Site limitations such as soil type, presence of rock or groundwater
In some cases it is possible to make broad statements regarding root systems of a particular family or genus. In other cases
you must look to the species level, to a particular plant's native habitat and other features, to determine moisture preference
and it's potential ability to prevent erosion. Many drought-resistant plants survive because their roots are long enough to
reach groundwater. Such a plant may have a taproot, which is a long, thick, single root, something like a carrot, or it may
have wide-spreading roots, like those of many trees, that reach out in all directions seeking moisture . Some perennials have
thick, fleshy roots that store large quantities of water, while many grasses have a deep fibrous root system that helps hold soil
and find soil moisture . Unfortunately, the root systems of many of these individual species have not been studied.
Information on native grasses and forbs is from Weaver et. al. Information on traditional biostabilization plants (e.g. willow)
is from Sotir et. al. Explanation of Symbols: (sprdng. =spreading)(?= Information is currently unavailable). Research on
native prairies, esp. by John Weaver et. al., shows us that prairie grasses and forbs are likely to be useful to biostabilization.
His studies of tall-grass prairie, in particular, reveal that "the struggle for water has resulted in the development of deeply
penetrating and usually widely branching root systems". In fact, the drought resistance of most plants is, to a large degree, in
direct proportion to root development (number of roots and depth of development). However, plants can be weakened by
prolonged droughts (or by continuous close mowing). Either will prevent individual plants from completing their normal
growth cycle and developing normal root systems .
Zones Column
• Hardiness: Specific temperature zones have been mapped across the United States, and these have been translated into
variou s plant hardiness zone categories. Weather outside this normal range may negatively affect plant material. Austin is in
the middle of plant hardiness Zone 8 . All of the plants on the list are hardy in our area.
• Hydrozone : A hydrozone is a portion of a landscape in which plants with similar soil moisture regimes are grouped together.
Using a hydrozone approach, a designer will carefully try to coordinate the moisture requirements of a specific species with
soil moisture "supply". The plant list uses a coding system that reflects the extremes of soil moisture conditions that are
typical of some streambank stabilization projects. This system is being proposed by the author as a way to explain the
moisture require ments of a certain species through the use of an abbreviated code. However, since it is not a standard
method that is in general use throughout horticultural science and the landscape industry, I have provided a thorough
description of its ' use (see Appendix 1 ).
• Sun/Shade: Light conditions are expressed using the following symbols: S =full sunlight conditions, PS= part sun, PSh =
part shade , Sh = Shady conditions
Comments Column
• Installation Notes: The form of the plant which is currently most available is listed fust. Rooted can mean containerized,
bare-root, or transplanted from another area . If seed is an ·option, the seeding rate is listed on a pounds per 1000 square feet
basis. These rates are presented as if the species is to be seeded by itself, and complete coverage is desired. If a seed mixture
is used, the designer will need to modify the rates of individual species appropriately.
• Tolerances/Preferences: A plants ' tolerances and preferences regarding moisture and soil are noted.
2
I
.I
Table 1 -Plant List
This plant list is for informational purposes only. All responsibility for project success or adequacy remains with the designer
who prepares the plans and/or specifications.
Plant Character Zones Comments
Botanical Na me Plant Ht./ Root Hard Hydro Sun/ Notes on installation, design features ,
Common Name Type/Use Wide system iness zone Shade tolerances, preferences, etc .
Andropogon gerardii Clump 6' fibrous 4 FU-L S,PS Rooted , seed : 2 lb ./pls, tillers; prefers moist
Big bluestem grass 3' deep PSh soil, occsnl. poor drainage, roots can reach 12'
Andropogon glomeratus Clump 4 ' fibrous ? FW-M S,PS Rooted , seed : 2 lb ./pls, tillers; needs moisture,
Bushy Bluestem grass 3' fluffy seedheads
Anisacanthus wrightii Deciduous 4 ' ? 8 U-VL S,PS Rooted , seed; seedlings colonize, prefers good
Flame Acanthus shrub 3' drainage, red-orange flowers attract hummers
Bouteloua curtipendu/a Clump 3' fibrous 4 U-VL S,PS Rooted, tillers, seed : 2 lb ./pls ; pioneer plant,
Sideoats grama grass 3' deep PSh prefers well-drained soils
Bouteloua graci/is Sod 8" fibrous 5 U-VL S,PS Rooted, seed: _ lb ./pls, stolons; sod-former,
Blue grama grass varies takes extrm drought, poor soils
Bouteloua hirsuta Clump l ' fibrous 5 U-VL S,PS Rooted , seed: _ lb ./pls; shallow, sandy or rocky
Hairy grama grass I ' soils
Buchloe dactyloides Sod 8" fibrous 5 U-VL S ,PS Rooted , seed : _ lb./pls, stolons; sod-former,
Buffalograss grass varies takes extrm drought, poor soils
Ca/lica rpa americana Deciduous 6' ? 7 FU-L Sun to Seed, fast growth rate, poor soils , rose-purple
American beau tyberry shrub 5 ' Shade fruit, wildlife food
Carex Emoryi Herbaceous 2 ' fibrous 5 0-M S,PS Rooted , rhizomes , seed ; grassy-looking sedge,
Emory's Sedge emergent varies PSh prevalent in local creeks, species rep. of genus
Cepha lanthus occidentalis Deciduous 12 ' ? 5 0-M S, PS , Seed, wet soils, can become treelike , fragrant
Button bu sh shrub 10 ' PSh summer flowers attract bees
Chasmanthium latifolium Clump 3' ? 5 F-L PSh , Tillers, rhizomes , seed: 2 lb ./pls , prefers
Inland seaoats grass 2' Shade moist , shady areas , distinctive seedheads
Cornus Drummondii Deciduous 20 ' sprdng . 4 F-L S,PS Dormant cuttings , root suckers form thickets ,
Rough leaf do gwood tree 15 ' PSh seeds, tolerant , esp . of wet soils, short-lived
Cype ru s ochraceus Herbaceous 18" surface ? FW-H S,PS Rooted , seed; thi s species representative of a
Pond Flatsedge emergent 8" vast ge nus
Eleocharis monteviden s is Evergreen 18" fibrous ? FW-M S,PS Root ed , rhi zomes, seed ; common and prevalent
Sand spikeru sh gmdcvr . varies in mo st wetlands, deep gree n color/texture
Elymus ca nadensis Clump 4 ' fibrou s 4 F-L S,PS Seed , tillers ; cool-season , vigorous seedlings ;
Canada wildrye grass 2 ' PSh be gins growth in earl y fall , nodding seedheads
Eysenhardtia texana Deciduous 10' ? 8 U-VL S ,PS Seed ; leguminou s
Kidneywood shrub 6 ' fra grant s ummer blooms, wildlife food
Forestiera pubescens Deciduous 8' sp rdn g . FU-VL Sun to Root ed, se lf-la yeri ng, seed ; may form thickets ,
Elbow-bush shrub 8' Shade poor soi l, va riabl e form , adaptable
Malvaviscus Drummo ndii Herbaceou s 4' ? ? U-VL S un to Ro oted, seed , seedl in gs colonize; red flo wers,
Turk 's Cap shrub 4 ' Shade adaptab le
3
i\o
Plant Character Zones Comments
Botanical Name Plant Ht./ Root Hard Hydro Sun/ Notes on installation, design feature s,
Common Name Type/Use Width system iness zone Shade tolerances, preferences, etc .
Muhlenbergia lindheimeri Clump 4' fibrous 7 FW-VL S,PS Rooted , tillers , seed : 2 lb ./pls, calcareous soil s
Lindheimer muhly grass 4' deep PSh near streams, Fall plumes
Panicum obtusum Sod 2' fibrous ? F-VL Sun Rhizomes, stolons, tillers, seed : I lb ./pls
Vinemesquite grass varies often grows in pure stands
Panicum virgatum Clump 10' fibrous 4 FW-VL S ,PS Seed: I lb ./pls , rhizomes, tillers ; best in moist
Switch grass grass 6' deep soils, spreads aggressively
Parthenocissus quinquefolia Deciduous 15' fibrous 4 F-VL Sun to Rooted, runners ; fast growth , tolerant , climbs
Virginia Creeper gndcvr/vine runner Shade tree trunks , fall color, wildlife food
Rhus aromatica Deciduous 6' sprdng. 3 F-VL S,PS Rooted, seed, root suckers ; colonizes to form
Aromatic Sumac shrub 5' PSh thickets , fall color, wildlife food
Schizachyrium scoparium Clump 3' fibrous 5 FU-VL S,PS Rooted, seed : 2 lb ./pls, tillers ; adaptable to
Little bluestem grass 2' deep various soils & moisture; dense root system
Sorghastrum nutans Clump 4' fibrous 4 FU-VL S,PS Rhizomes, seed : 2 lb ./pls, prefers moist,
Indian grass grass 4 ' deep fertile soils, yellow fall blooms
Sorghun1 halapense Clump 6 ' fibrous FU-VL S,PS Seed, rhi zomes, tillers ; weedy non-native that
Johnson Grass grass 4' deep has naturalized, seed prevalent in urban soils
Sporobolus airoides Clump 4' fibrous ? F-VL s Seed , tillers ; restricted to hill country & west,
Alkali sacaton grass 3 ' withstand s flooding
Taxodium distichum Deciduous 80 ' surface 4 0-L S,PS Rooted ; wet soils or dry ; very durable ,
Bald Cypress tree 40 ' to deep natural armor for stream toe
Tripsacum dactyloides Clump 6' fibrous 6 F-L S ,PS Rooted , rhizomes, seed: 2 lb .pis , long-lived
Eastern gama grass grass 6 ' deep PSh dense clumps, seasonal poor drainage o .k.
Appendix 1
The Wet/Dry Hydrozone Coding System
This system uses a combination of letters as a code to indicate the moisture level of plants ' native habitat and relative soil
moisture preferences and tolerances . A plant is much less likely to survive if soil moisture le vels are outside its' range of
adaptation . While some plants will use and transpire all available water, others will "drown" when given too much water.
Conversely, many species are intolerant of drought. Fortunately, many plants are tolerant of a wide range of soil moisture
conditions . The Wet/Dry system was designed to accommodate plant diversity . The hydrozone code will give an approximate
range of moisture le vel preferences for a particular species . However, these codes merely give a general indication of moisture
level for the plant. Other factors come into play regarding moisture needs of plants , such as the plant 's age and size , the
composition of the soil , the time of year and the weather.
Wetland Occurrence
The fust portion of the code is an adaptation of a system that is well-established in botanical and ecological science . The system
and a comprehensive plant list can be found in a publication entitled "National List of Plant Species That Occur in Wetlands:
South Plains (Region 6)". In this system, the letters indicate a ·range of estimated probabilities (expressed as a frequency of
occurrence) of a species occurring in wetland versus non wetland across the entire distribution of the species. These indicators are
used on a national , as well as a regional level. In the Plant List, the indicators that have been established for the Texas region are
used. The Indicator cate gories should not be equated to degrees of wetness. Many obligate wetland species occur in permanently
or semipermanently flooded wetland s, but a number of obligates also occur and some are restricted to wetlands which are only
temporarily or seasonall y flooded . Please refer to the chart and the diagram below.
4
Letter
C ode
u
FU
F
FW
0
Zone
Cate o
Upland
Facultative Upland
Facultative
Facultative Wetland
Obligate Wetland
Table 2 -Hydrozones: Wetland Plant Occurrence
Frequency of Occurrence in Wetlands
(under natural conditions)
Occur almost always (probability >99%) in uplands (nonwetlands)
Usually occur in uplands (probability 67% -99%, but occasionally found in wetlands
Equally likely to occur in wetlands or nonwetlands (probability 34% -66%)
Usually occur in wetlands (probability 67% -99%), but occasionally found in uplands
Occur almost always (probability >99%) in wetlands
Moisture Requirement
The second portion of the code generally indicates potential drought tolerance of a particular species. Table 3 explains the
various levels of drought tolerance. Be aware that the drought tolerance codes assigned to each species in the Plant List are
preliminary; they are simply "suggested" for your consideration. Unfortunately, except for certain crop plants and most turf
grasses, little research has been done regarding the specific moisture needs of most plants. The information presented in the Plant
List has been derived from the following sources :
• observation of the plants in their native habitat (particularly during droughts)
• scientific and horticultural references
• and communications with landscape professionals
The hydrozone codes used in the Plant List assume that:
• the plant is established, and at an average mature size
• the plant is placed located in soil conditions appropriate to the species
Conditions that vary from these will affect the moisture preference of a plant. For instance, newly installed plants need frequent
watering during their "establishment period". If a plant is placed into an inappropriate soil, or soils far from the average, then
moisture needs are likely to vary. Generally, when temperatures are moderate then the "water-demand" of a plant will be
relatively moderate as well . Timing of soil moisture is also important. Dry weather during our region 's normally wet spring will
affect most plants for the entire growing season. Adequate moisture during the last half of the growth period will not compensate
for an inadequate supply during the first half. Stunted growth with little foliage will be the result.
Table 3 : Hydrozones -Moisture Requirement
Moisture Native Frequency
Moisture Requirement Landscape that Moisture
Level Hydrozone Exam le Is Needed Ex lanation of Drought-Tolerance
D Very Desert to Quarterly Plants in this zone are very drought-tolerant and will
R Low Short-grass Prairie thrive even during typical summer drought conditions .
y
Low Short-grass to Monthly Plants in this zone should survive on natural rainfall ,
Tall-grass Prairie though they may be stressed during very dry conditions.
Moderate 25 yr. floodplain Weekly Plants in this zone need soil moisture on a regular basis ,
M Riparian whether through rainfall or access to groundwater.
0
I
s High Water's edge to Daily Plants in this zone need soil moisture on a regular basis,
T Wetland fringe whether through rainfall or access to groundwater.
w High Wetland marsh Constant Plants in this zone are wetland plants that need
E to deep Pond constant access to wate r.
T
5
The information and plant list presented in this document is necessarily a composite of many people 's knowledge , opinions , and
experience. Every effort has been made to transcribe this information accurately; please report inaccuracies or alternative
opinions to the author. Information was obtained from the following literature .
Correll , Donovan S ., and Correll, Helen B . 1972 . Aquatic and Wetland Plants of Southwestern United States. Environmental
Protection Agency 1777 pp .
Gray, Donald H., and Sotir, Robbin B ., 1996. Biotechnical and Soil Bioengineering Slope Stabilization: A Practical Guide for
Erosion Control. John Wiley & Sons, Inc . ISBN 0-471-04978-6
Reed, Porter B . 1988 . National List of Plant Species That Occur in Wetlands: South Plains (Region 6). U.S . Fish and Wildlife
Service , St. Petersburg, FL NTIS publication #PB89-169932 95 pp.
Wasowski, Sally, and Wasowski, Andy. 1991. Native Texas Plants, Landscaping Region by Region. Gulf Publishing Company,
Houston, TX ISBN 0-87719-111-5
Weaver, John E ., and Fitzpatrick, T . J . 1934 The Prairie. From Ecological Monographs, Volume 4, pages 109-295. Published
by Duke University Press, Durham, North Carolina. (Reprinted 1980) Prairie Plains Res_ource Institute of Nebraska. 295 pp .
Reed Park
• Use of Biologs
• Natural Character
Bridgewater Soil Lifts
6
Pecan Springs:
Fabric-wrapped
Soil Lifts
Skills for Landscape Architects
• Knowledge of plants
-Biological needs
-Availability
• Sense of aesthetics
• Write tight
specifications
I .
Stream Geomorphology and Design
•Introduction to Classification
•Rosgen
•Channel Evolution
•Applications
•Stable Channel Design
•Threshold Channels
•Alluvial Channels
•Stability Analysis
•Lane's Balance
•Analytical
1
Why do people classify things?
Psychologists the orize th at in a universe of lim itless
numbers of objects and id eas, classifying things into
group s is one of the brain's mechanisms for cr eating
order out of ch ao s.
Fluvial Classification: Neanderthal Necessity or Needless Nonnalcy -
Craig Goodwin (A WRA, 1999)
Historically, most fields of science have gone through a
classification phase. The classification phase usually
occurs during the early stages of development of a
scientific field as a means of ordering observations and
descriptions. As a science advances, classification gives
way to the development of empirically based laws and
finally to theoretical understanding.
Fl uvi al Classification : Neanderthal Necessity or Need less Normalcy -Craig Goodwin (A WRA, 1999)
3
Different ways to c ~a , . Qf characterize a
compli
• Existing Geomorphic
Conditions
• Evol ution
• Riparian
• Biota
• Base Flows
• Water Quality
• Dissolved Oxygen
• Others
Scale of Classification
• Region Scale
• Landscape Scale
• Stream Corridor Scale
• Stream Scale
• Reach Scale
1
s
~
R -'
Stream channel types and their characteristic stability problems
Channel Type
Mountain torrents
Alluvial fans
Braided rivers
Arroyos
Meandering rivers
Modified streams
Regulated riven;
Deltas
Typical Features
Steep slopes
Boulders
Drops and chutes
Multiple channels
Coarse deposits
Interlacing channels
Coorse sediments{usually)
High bed load
Infrequent flows
Wrde flat channels
Flash floods
High sediment loads
Alternating bends
Flat slopes
Wide floodplains
Previously channe&zed
Altered base levels
Upstream reservoirs
Irrigation diversions
Mulliple channels
Fine deposits
Stabili~ Problems
Bed scour and degradation
Potentia l for debris flows
Sudden channel shifts
Deposition
Degadation
Frequent shifts d main channel
Scour and deposition
Potentia l for rapid changes in planform , profile, and aoss section.
Bank erosion
Meander migration
ScoJJT and deposition
Meander development
Degradation and aggradalion
~k emsion
Reduced actiVJly
Degradation below dams
Lowered base level for tributaries
Aggradation at tributary mouths
Channel shifts
Deposition and extension
EM 1110-2-1418, USACE, 1994
6
Stream Classification Systems
Davis (1899): Tirree classes based on relative stage of adjustment: youthful , mature, and
old age .
Leopold and Wolman (1957): Classifies rivers into braided, meandering, and straight.
Strahler (1957): Classify streams by order. The uppermost channels in a drainage
network are designated as first order down to their first confluence. An intersection with
a stream of the same order raises the order below the confluence.
Thornbury (1969): Classify by history of development of land use . Antecedent,
Imposed, Consequent, and Subsequent.
Schumm and Meyer (1979): Process based classification approach which attempts to
systematize the relationship between planform, geometry and process.
Montgomery and Buffington (1993): Classifies six classes of alluvial channels by
sediment source, supply, storage and transport processes, bedform pattern, channel
slope, confinement and pool spacing.
Schumm, Harvey, Watson. (1984) and Simon (1989, 1994): Classify streams by
developed conceptual channel evolution models that describe a predictable sequence of
changes a stream undergoes after certain types of disturbances.
Rosgen's (1994): Classifies streams into eight types based upon channel form, cross
section geometry, and sinuosity.
Simon {1989): A channel evolution model. Classifies by expected trends in a disturbed
channel. Includes a step that addresses constructed channels.
lJSACE EM 111 0-2-14 18. 1994
7
Stream Classification Systems
Existing Conditions
Strahler (1957): Classify streams by order.
Strahler (1957): Classify streams by order. The uppermost
channels in a drainage network (headwater streams with no
upstream tributaries are designated as first order down to their first
confluence. The intersection of a a channel with a lower order does
not raise the order of the stream below the intersection. Correlates
best within a basin.
8
Montgomery and Buffington (1993): Classifies six classes of
alluvial channels by sediment source, supply, storage and
transport processes, bedf orm pattern, channel slope,
confinement and pool spacing.
Table 2. Cl1amcferistics or different types of s1ream rcachc• (modified from Bisson and Monlpncry (1996 )).
Pmlomhwlt
bed matulal
Bed form
pa ti em
Dumlnant
rougllana
elemen ts
Typical slope
("A)
Typlclll
~
Pool spitdng
(da1u ..
widths)
TYPlca.I Bed
M •terti•I
Bed form
Pattern
Domln.,..t -· s .........
Typlcel 8 -
(m /m)
Ty p ica I
Confin ement
Pool Sp-.cing
(Channel
W idths)
CoUavlal Bedrock
Variable Dodrock
Vari.Ible Variable
Dou.ldctf, Suoambed..
lar,c woody """"' <kbrio
>20 v-
StroeiJ.11 St~a:ly
..,.Rned ronfirttd
V•iablc V.n.l>lc
CaS«ck S~p-Pool Plane-bed PooJ.rillle
llo.s.ldct CCtbbldkuldet Gta,·t l!cobbl Guvd
<
None Oooillacu NOAC" 011allm•
.miwly i.-~y
Bov.ldcrs, StC"p1 A. pool•. 9\>Wdcn., Bvs&.poolt..
lw>k. boeldc.ta, Wac cobbles. booldm.t ,..O(Hf, dtbri.t, buq cobbla,. lfr11c
Nab 'tlr'Oody.dr:bri1,
rirn1olil)>,
buU
S-30 •-8 1 -4 0.1 -2
Suonaly Mod«>tdy VMiliblc> ~Afined
confined c:cmAD:c-d
<I 1 .. N00< $-7
Rq:lme Braided
S&rul -
~lriltycnd Ot<;;llws
bi<nlly
Si.a~ty , Bau4pools
daM .... rippJ6
A:bu5,buk$
<0.1 <3
Un.con:flae.d Unconfiatcl
j-7 Variabk
9
Stream Classification Systems
Rosgen's (1994): Classifies streams into eight (now nine) types
based upon channel form, cross section geometry, and sinuosity.
Applied RivCT Morphology -Dave Rogsen
Geomorphology: Dimension
(width, depth & cross sectional area)
•-------topographic floodplain-------~
------hydrologic floodplain-----
StrCllltl Corridor Reslontion' Priociplcs. Proccsscs, md Pncticcs. 1998
Geomorphology: Pattern
(meander width, bend radius, riffle & pool spacing)
Strcm:n c.onidor Restoratioa: Principles. L I 0 14 W Processcs.andPrxti<:es,1991 • = -
• Re = 2.3 - 3 .2 W
1
Geomorphology: Profile
(average stream slo pe, riffle, & pool slopes)
• Ri ffle Slop e= 2 S
• Poo l Slope = 1/2 S
• Pool Depth = 2.5 D
• Pools = 5 -7 W
·--------------------------------~~~
Pro111e
POOL AND FUFPLE SEQUENCE
The River Book -James Grant
MacBroom, 1998
14
Emphasizes dimensional properties of entrenchment ratio , width-depth
ratio , sinuosity, sediment size and channel slope.
t
~ \ 'I \\ n El' 111
I\ ..-B.\\hTl LL\\ ID 111
1
Rosgen's Entrenchment Ratio
(Access to the Floodplain)
Slightly Entrenched: ER >2.2 (C, D, E)
+----------------------------------------~
----Flood-prone area
Q 5
Moderately Entrenched: 1.4 < ER < 2.2 (B)
Flood-prone area +or-0.2
Q 1.5 Slide modified from Lyle Steffen
2
Many classification systems concentrate on
fluvial forms, which are the products of a
complex, dynamic system.
Input: Water,
sediment quantity,
sediment size
Constraints : Val ley slope,
valley width , boundary
constraints, man made
con straints
Fluvial Processes :
f"'"l.-1~ Erosion, Sediment
Transport, Deposition
Channel type
Reach features
I Morphodynamic F eedb ack I
M any flu v ial classification sc h emes have been based
w holly or in part upon characteristics of channel form.
Channel forms, although readily measurable, are the end
products of complex, dynamic systems. These end
products may be non-unique manifestations of underlying
controll ing factors and processes . The lack of a one-to-one
correspondence between geomorphic process and form
su ggests that measurement of fluvial processes or
controlling factors , albeit di fficu lt, may be a better
p athway to discov ering natural kinds of river s . 1
I-Improving Future Fluvial Classification Systems -American Water Resources Association , TPS-99-3, Craig N .
Goodwin
19
Cha11nel Evolution Models
Schumm, Harvey. Watson (1984): A channel
evolution model. Classifies by expected trends in a
disturbed channel .
Stable Floo~aJn
11 Incision ~--Q,
IV Stabilizing
v
Stable
h=bank ht
hc=attlcal bank ht.
Tern.ct1
b < h~
b >b.
(11 .. dculllnR)
b> b,
(Bank FaUuro)
b -b,
Ttrract1
b <b,.
I kta_dcut5
5 1· nc,i" s i o rt --+o p 4-o bo tfrJYYJ
lr0 &1.0ll Dn ,·11&-f~ f t[)~fcle__
op f?~d >
1
--~-o. ... -
Advantages of Stream Classification
•Communication -Provides a common language
for discussing streams and their attributes.
2
Adva11tages of Stream Classificatio11
•Standardization -Forces practitioners to
measure things in a standard manner
•Encourages thinking about stream processes
•Provides a basis for generalizing and
extrapolating data, knowledge, treatment
strategies, and testing hypotheses about stream
systems.
Stream Classification has also been used for:
•Prediction -Used to predict a river's behavior from its
condition and/or dimension, pattern and profile. (not
universally accepted)
•Extrapolation -Used to extrapolate data from a few sites or
channels to a much larger number of channels over a broader
geographic area . (use caution)
•Defining~a Target -Used to define the stable or desired
form and to set targets or objectives for restoration or
rehabilitation.1 (reference reach).
•Defining the scope of a problem -Provides a means for
quantifying the size of the problem and the type and size of
the responses needed to address the major issues.
Sensitivitv by classification
Rosgen Stream Sensitivity to
Tvoe 0 isturbance
Al,A2 ,Bl,B2 Very Low
B3, Cl , C2 , Fl, Low
F2 GI
B4, BS, 86, C3, Mode rate
Oa4, OAS , DA6,
F3 G2
A6 , 06, E3 High
C4 , CS , C6, 03 , Very High
04 , OS , E4 , ES ,
E6, FS , F6, G3 ,
G6
G4, GS Extreme
Sensitivity to increases in stream flow magnitude as well as scdi~t in~i!'
3
--Poa111* Tf'latmllnt Options CEM--Cl-··-A.8 .C,O,E, ........ w.i.rlhed nn>tl d.me and aedlme.nl
0 loedl. Mlllnl-'" rlpa1.n V11g1tlation. MIHlloln gr.te.
Spot treatn.nt1 t:I IOI bloengWMl.,tng ..
'_.:.___.et•. ,_ O,F Grlldll oonlrot, c::Nrv* rulgnnwnt. M c:n.nn... Do not UH..., __ .:......._ __ ...__ "°"9. J-F, B E.Jplnd cNnnel flf'dlor exCWllAe • ~ .... Shape bMlb lo r9d.lcti lkelhood d ltq>ll f.Ue .
""""" ...,... cb ... bl proteclon. Improve ~wt ... ·--•.eon. Do no4 UM.._, -'one. J-C,E MMUln Wlllenhed runoff d..me tnd Mcli-nent ........ loeda. ~ ch*VMI arKUor nc.v• • -loodpWn. Shape b9i'lk1 lo rwd..lce lkMhood of
.. , ..... Inst .. duteb'9 bl prot.clon. impftw• __ .,_ ... _
.. -..! ..... J-C,E Shape bw\ks b:> ~ llk.thood ol "°fle ,...,... ......... Inst .. dwat>ie bl ptOtac:tion. lmpfow '1*fan .. _
.. _:......, ......... M.lntlllngrllde.~scl I ~____.__ ............. _ as __.:_ _ _. __
• F,8,C,E Mlifntairol w.,.9Md n.noll'd..me and ~ .......... loads, lmprow rtp.-lmn vegellltion. Ma6nl.liln grlde .
Inst .. .,. prolKtion, l~sol~ .. -..... == ··-C,E Mmnl*I -a.nn.d n.noll' volume tnd Mdmen1
kle!M. MM-It.in Ripwi., ~-~
__ ...
grade. Spot tre.unents of d bloenglrw.tng .. ......... .,....,_ _,,.,.,....., __
I :____.ele . = ... _...,.
Disadvantages of Stream Classification
•All stream classification systems have limitations that
are inherent to their approaches, data requirements and
range of appropriate applications .•
• Key parameters such as bankfull flow or channel -
forming flow or discharge, or critical bank height, may be
difficult to determine or inaccurate leading to
inappropriate classification.'
•It is difficult to include dynamic processes, time frame,
and concepts of equilibrium or geomorphic thresholds in
some classification systems, which assume the stream is
in a fixed state. ' "''""'''""_""'""' __ ....., ...
You need to get
enough
information to
know what you
are dealing with.
-Objectives/Goals
•Dominant Processes
•Constraints
•Existing Conditions
•Future Conditions
-1 • ..,.,.,..1.~flf .. a-i .... ,,... .. u.w --.
Dr.S.-.......... c-llrc.-1 .................. 0..
••· . LwaADC~-..,,
4
5
6
Components of Grade Control
Structures
• Control Section
• Energy Dissipation Section
• Adjacent Protection
• Spacing
Limiting Slope Criteria
H
x==-----
Where:
x = length between grade control structures
H = amount of drop removed in reach between the weirs
S0 =original bed slope
SL = limiting slope
The limiting slope can be calculated or approximated as 0.5 the bed
slope in steep streams and 0. 7 the bed slope in mild gradient
streams.
36
Note:
•No flanking protection
•No control section
1
stone toe with willows
2
3
4
5
-• Stream system unstable
• Increased resistance increase flood levels
Excessive velocities
• Tolerance for movement
• Site dependence
Deep failures
• Failure to grow
May be uprooted by freezing and thawing
May be damaged by ice and debris
• Wildlife and live stock can feed on it
Maintenance
Other issues
Channel Design
Definitions
• Tirreshold Stream: The channel boundary material
movement is negligible during the design flow.
• Alluvial Stream: Bed and banks formed of material
transported by the stream under present flow
conditions
Vegetated Banlcs
and Stable Beds 1---'~• Can it be left alone?
yes
Design to move sediment
load through reach with
appropriate sediment transport
theories and equations
Then leave
it alone
Allowable velocity, tractive
stress and regime equations
6
Threshold Streams -Design
Approach
• Allowable velocity
-grass and other vegetation
-sand and earth
-protective lining
• Critical shear stress
-gravel and cobbles
-rock lining
7
The average shear stress exerted on a ch annel boundary can be
estimated with th e equati on provided below assuming the flo w is
steady, uni form , and two-dimensional .
•o = yRS,
where
't0 = average boundary shear (lb/ft 2 )
y =specific weight of w ater ( 62.4 lb/ft 3 )
R =hydraulic radius (A/P, but can be approximated as
depth in wide channels)
s, = friction slope (can be approximated as bed slope if
flowing as normal depth)
NOTE: Avera u
8
-N < = -.Q -... cu
G> .r::
UJ
iii u :o:; ·c:
0
Critical Shear Stress for Quartz Sediment (Shields 1936, Lane 1955)
1
0 .1
0.01
0 .1 1 10 100
yRS r f-1 ____ s_e_d_im_e_n_t Size (mm)
Adapted from ASCE Eng. Practice Standard No. 54
EM 1110-2-4000
5
I
f
,,,_..,.cl_.-IO lll'!'lGM-1'71)
I! II
;! I'' i j II :::=!·-' I! • ""."'
'""'......., ~.ocil'J JlllCIMt ....
I Ii I I I Il l ::::::.,
Agure ~1. Shields cu rve (ASCE 1975)
-t,.•r ........
J.Clf
UJ
2.J
U$
u•
UI
59
There is allot of guidance in the literature
_i.~ ........ ,.... __
..... ~ ... _,,,...,.,~..., --· ......... _,., .. .-l*tM•--) ---__ _., .. M, __
lnu.11111.t ....,_._._
... 11 ..... ,....,,,...., __ _ ......... ......... -
~-
.,.._, __ ,.. .. w.i: .... ~ .......
-~.-··--,.. .. ~ ..... s-10-.
__ ,,.., __ ... ,.. .......... -10'!'
.~
"'--.. -.... -... .... ,,.,_
.. 5-1D'llO•-
..
aw.~-·'"'
••• USJCl!mn11 ..
Sdllitdll1Ma.ttl,t"4
,__.,tNl
1.2 400 ......... tMl
t.5 "° ai.n ....... ,_
0.017 . ..,,
OR U .....
OA lO ,_.
12 .... ...
us 1 ·'"°
2 .tMO
' 2.S T ....... tNO
USOA.1M7
USOA..1"'7 , .. , , .. ,
I But be careful...
Limitations
• Max permissible velocity or tractive force cannot predict
the conditions needed to transport incoming sediment
supply.
• In bends or meandering channels, bank erosion &
migration may occur even if stress or velocities are
within allowable limits .
• Unique combinations of width, depth, slope are not
defined.
• Shear stress is computed for flat beds, and sand beds are
usually in dunes or ripples .
1
Degradation through armor layer
Alluvial streams
• Mobile boundary
• Roughness variable
• Sediment transport significant
• Potential for general deposition and/or scour
2
To determine one independent
Variable (w,d,S)
• Analogy Methods -conditions in one reach
can be copied to another.
• Hydraulic Geometry Methods -stream
behave in predictable way
• Extremal
3
Analogy Issues
• Reference must be stable
• Reference must have same channel forming
discharge
• Referance reach must have similar
hydrologic, hydraulic, and sediment inflow
conditions
Hydraulic Geometry Issues
• Width or slope is a function of channel-
forming discharge
• Data Scatter -all points potentially valid
• Watersheds must have similar history,
physiology, hydrologic regime,
precipitation, vegetation, etc
4
• W.....f.sll
-~1"7Z>
l E.MNl(lln}
·W....11'111
. ...,.,_11 ... 1
. ,,..,,,,.,.,
·~-._,,.,.,
• ....,.,..,Tl'llllM flte9)
•a....11•11
_,....An..aO...
i ••f-"-""""_c;;.c~·· ... =-~~+c-.::::.~~~~+-~~~~~ • f
I
Figure S-6. Downstteam widdl bydnulic g<o~ror Nonh American riven,
If'" l ·6l{t', and U.K. gravel-bed riven, If'" M 9 Q, .
H)'69Wk: OUp orSCftml RA:~ PYojimJ.CopclMd.
Mee-. nor., So., ..df . lOO I USA.CE
Planform
Analogy method
Reference reach
• Stable reach
Similar watershed streambank and streambed
conditions
Hydraulic geometty
• Composite relationship
• Data Scatter -all points potentially valid
• Watersheds must have similar history
5
6
Channel Forming D ischarge
(dominant discharge)
A single steady discharge that, given enough time, would produce
channel dimensions equivalent to those produced by the natural
long-term hydrograph.
Bankfull Flow -the maximum discharge that the channel can
convey without overflowing onto the floodplain.
Discharge for a Specific Recurrence Interval -assumed to
correspond to an annual flood recurrence interval of
approximately 1 to 2 .5 years. The 1.5-year recurrence flood has
been shown to be a representative mean of many streams
(Leopold, 1994).
Effective Discharge -the mean of the discharge increment that
transports the largest fraction of the annual sediment load over a
period of years (Andrews, 1980).
The channel-forming discharge concept is based on the idea that for a given alluvial channel geometry, there
exists a single steady discharge that, given enough time, would produce channel dimensions equivalent to those
produced by the natural long-term hydrograph. This discharge therefore dominates channel form and process
and may be used to make morphological inferences. Until the 1960s it was widely assumed that floods of great
magnitude, but low frequency controlled channel form because of the non-linear relationship between
discharge and sediment transport capacity. This view was challenged by Wolman and Miller (1960) who
demonstrated that in most streams over an extended period of time the total amount of sediment transported by
a discharge of a given magnitude depends not only on its transport capacity, but also its frequency of
occurrence. Thus, although extremely large events can produce spectacularly high sediment loads, they
happen so infrequently and last such a short time that their overall contnbution to the total sediment movement
during a long period is relatively small. Small events also make a small contribution to the total sediment
moved because their high frequency of occurrence is offset by their very low sediment transport capacity. It
follows from this logic that flow of both moderate magnitude and moderate frequency are responsible for the
greatest amount of sediment movement. Wolman and Miller defined "moderate frequency" as events
occurring at least once each year or two and in many cases several or more times per year.
All three methodologies listed above for estimating channel forming discharge present challenges . In practice,
problems often arise when attempting to identify bankfull stage in the field . Problems center on the wide range
of definitions of "bankfull stage" that exist (Williams 1978). Although several criteria have been identified to
assist in field identification ofbankfull stage, ranging from vegetation boundaries to morphological breaks in
bank profiles, considerable expertise is required to apply these in practice, especially on rivers which have in
the past undergone aggradation and degradation. Recurrence intervals for dominant discharge are generally in
the range of 1 to 3 years , but have been shown to vary widely ( 4 to 10 years) for different types of streams
(Pickup and Warner 1976). Calculation of effective discharge requires hydrologic and sediment data. Without
nearby gage data, effective discharge calculations require use of an assumed hydraulic roughness and selection
of a reliable sediment transport equation. In light of these challenges, it is recommended that all three methods
be used and cross-checked against each other to reduce the uncertainty in the final estimate of the channel
forming fl ow.
Hydraulic Design of Stream Restoration Projects , Copeland,
McComas, Thome, Soar, Jonas, and Fripp, 2001 USACE
77
Effective Discharge
08•""'~•1'*'8-ib)
.~ ......... ~(9J'bl --
Effect of Pis charge
Stable Width-Slope
Combinations
0.0 12 . ti~l~I
0 ~ I I I I I I ·
0 20 40 60 80 100 120 140
Width
--0=1200
....... 0=2800
-··--0=800
- ---O=BOOO
1
Stability Analysis
Sediment Impact -will it work?
Assess ability of design channel to transport inflow
sediment load.
The potential for assuring sediment continuity through a design re.ach
requires an assessment of the sediment budget, which is determined by the
magnitude and frequency of all sediment-transporting flows and the
sediment supply. Mean annual sediment load from each reach is calculated
by numerically integrating the annual flow-duration curve with a bed-
material sediment rating curve. To attain geomotphic stability through
sediment continuity in the medium-to long-term, the mean annual
sediment load for the design channel (capacity) must match the mean
annual sediment load in the supply reach (supply). The sediment impact
assessment is a closure loop at the end of the design procedure to: 1)
validate the efficacy of the design channel geometry; 2) identify flows
which may cause aggradation or degradation over the short term (these
changes are inevitable and acceptable in a dynamic channel); and 3)
recommend minor adjustments to the channel design to ensure dynamic
stability over the medium-to long-term. This can be accomplished using a
sediment budget approach for relatively simple projects or by using a
numerical model that incorporates solution of the sediment continuity
equation for more complex projects.
An Overview of the USACE Stream Restoration Guidelines , Fripp, Copeland , and Jonas , 2001
81
Definitions
• Aggradation: Long term sediment deposition.
• Degradation: Long term removal of sediment.
82
Sediment transport: Lane's balance (1955)
Qs , <ls o
Aggradation
S*Q ~ Qs*dso
d50 =median particle diameter
Os = discharge of sediment
Q, s
Degradation
S =slope
Q = discharge
There are lots of different relationships out there that relate energy and load
variables. Lane's balance was developed/published in 1955.
This is a mental model, no calculators required, and it's a good way of
analyzing whether things make sense--a "Sanity Check"
Os • Dso ex. Ow • S
83
Lane's balance
S*Q ~ Qs*dso
Qs, dso
Aggradation
Q ,S
Degradation
More sediment, aggrades. More water, or a steeper slope -degrades, excessiv e
scour. Note that stream is still free to migrate laterally
Expected Response of Channel Characteristics to Changes in
Driving Variables
Expected Change in Ch1mnel Characteristics (Exceptions May Occu r)
Variable Subject
tol ~ Nature of
Change Change Width Depth Slope Platform Type Bank Erosion
Discharges Increased Increased Increased Reduced No m&lked Increased
change
Reduced Reduced or Reduced Increased or No marked Red uced
unchanged' unchanged• change
Bed-sediment Increased Unclear Reduced Marked increase lnaeesed bars May inc:reese
Inflows and chaMel
splitting
Reduced Unclear Increased Reduced Less channel Mayreduoe
splitting
Bed-sediment Increased Insignificant Reduced Marked increase Unclear Unclear
grain size
Reduced Insignificant Increased May reduce Unclear Unclear
Bank cooditioos Add bank May raduce May increase No marked As imposed Reduced locally,
protection locally change may increase
downstream
Removal Increased May reduce No change lncreesed bars Markedilla"~
of woody
vegetation
' Depending on availabiDty of sediment for deposition . EM 1110-2-1418, USACE, 1994
84
Q: Since the slope is increased, how is the balance kept?
Lanc·s balance
s•Q -Q,'d,,
1
Walla Walla River today
Sediment Models
• HEC-6
• BRI-STARS
•SAM
• other
Can estimate
Q
Time
• Volume of sediment moved for a given event
• Volume of sediment moved annually
2
Lane's Balance Example l
s•Q-Qs*d50
Aggraclation Degradation
Existing Conditions: Wide straight stream High bed load. Arca had been gravel mined
itional in areas. Braided in lower reaches
A single thread meandering slream
was coosidered more desirable far
aesthetic and habitat ~
3
Example 2
4
Limited Information
• No sediment records
• Nogage
• Q(2yr) = 1,300 cfs (regression)
Bank full regional regression = 800 cfs
• Upstream min width/depth 0 = 1.200 cfs
• Effective discharge = 900 c fs
Goal is sediment continuity
What we did have:
• Bed sediment samples
• Limited hi storical records
Hydrauli c m odel
Sediment Rating Curve
·-~ t ,...., --··-··-l
J '~: • i
I -I J to i
1 • J-·-·-..-·-. .:..
~l
Project l Area
5
Sediment Budget
~l
Project l Am.
Looked at
"""& 3'00 -f2'00 --OISPoojo<t
12000 --U'SP,q.ct
a: ISOO '-···""-'•' ...
1000 •• '..
~ . --
0.1 10
IOOOOtm l 1000 ••• l 100 ••
1 .· -~~--·
.!S 10 •• • ~ •
1 I •• ~. . .··~ ~-·
0.1 • •
~·-----... --~'°""""hi --· --U,S.ICMccrl .... . . . ....,.,,.,._,.,..
10 100 1000
w.w~tcttJ
YanL Acker-White. Lauscn-Cooeland, t..usen-Millcr, Mcvcr-Petcr and Muller. Toff-MPM
35
{ 30
§ ,.
"20 l t5 I ..
DC..,. ... ,._
e,,.,_P.q.d ··-
Scdimtnt rating curves in&egratcd wi th Oow duration to estimate an annual yieJd
Conclusion: Minimal change in sedimentation pattcms.
HEC-6 Example4
6
7
Data
•Current Geometry
•Highwater Maries
•Hydrology (40 yrs and storms)
•Rating curve
•Sediment
•Bed material
•Histori cal Geometry
~-i ~-l.U.U.W..1 u.ii+i+mu.m+m.i~,ti-H+f+.llH1
-.t-m#llll-l-ll-W-l+ll-llm.!+l+Htt+lt1fH+ •Dredge Records
Conclusion :
•Project as constructed is a
depositional reach
•Conveyance has been Jos t
•Will continue
•Storms will not flush
.. sediment ~-------l
Examine Alternatives :
•Do Nothing
•Sediment Trap
•Flood way
•Downstream Channel Improvement
•Geomorphic Channel
8
Doesn't eliminate all possibility of a
project not coming out as expected but at
least reduces the potential of a problem
9
Geomo rphic Thresholds and Sensitivity
c
~ l Limiting Thresholds
0 -----------
~
u > 2
Limiting Thresholds
.._ _____________ Time
A. C: Robust behavior: River repeatedly crossing intrinsic thresholds but overall
response stable within limiting thresholds . Landforms retain stable identity as
they form and reform.
B: Responsive Behavior: River moves across extrinsic threshold to a new
process regime in response to externally imposed changes. Landforms in A are
destroyed and replaced by new landforms in regime C.
Extrinsic Threshold: One that is exceeded by the application of a force or
process that is external to the system. As the flow in a river is increased over a
bed of potentially mobile particles, the shear stress is increased. Eventually,
the submerged weight of the particles can not resist the forces applied and the
particle becomes mobile. When this occurs, the particle has crossed an
extrinsic threshold (the threshold of motion). Other examples: climatic
fluctuation, an ill planned bank stabilization project, an earthquake, land-use
change, base level change
Intrinsic Threshold: One in which change occurs without a change in an
external variable. The capacity for change is intrinsic within the system.
Example: long term progressive weathering leading to slope failure,
development of a meander cut off.
Other terms used in threshold theory include:Transitive-the new state is
persistent and Intransitive-the new state is short lived
Applied Fluvial Geomorphology for River Engineering and Management -Thome, Hey, and Newsom 1997
Systems reaction and relaxation
T ime-
11 0
Interdisciplinary and linked
1