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4 Stage Two, Step Three: Interpret and explain the geomorphic condition of the reach

4 Stage Two, Step Three: Interpret and explain the geomorphic condition of the reach

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317



Stage Two of the River Styles framework



Figure 10.9 Interpreting and

explaining the geomorphic condition

of a reach. Modified from Fryirs (2003).

Reprinted with permission from

Elsevier, 2003



in context of its evolutionary sequence, identifying whether irreversible geomorphic change has

occurred. River condition is framed relative to a

defined reference condition to determine how

far from “desirable” the geomorphic structure

and function of differing reaches of river are.

Procedures and decision-making processes used to

assess the geomorphic condition of reaches are

summarized in Figure 10.9.

10.4.1 Determine reach condition using the

degrees of freedom and good, moderate, and

poor condition matrix

A matrix is developed to assess the condition of

a reach, whereby the practitioner assigns ticks

or crosses in answer to the table of “desirability

questions” constructed for each River Style.

Procedures used to measure each geoindicator are

presented in Table 10.4. Each relevant geoindicator must be measured and interpreted to gain a full

appreciation of the condition of the reach and to

answer “desirability questions” appropriately.

Once fieldwork is completed, the results are synthesized across the entire reach, comparing the observed conditions with the reference condition.

Depending on the number of Yes/No responses to

questions asked about the “desirability” of reach

character and behavior, a tick is assigned for each

degree of freedom. For example, revisiting Table



Table 10.9 Determining the geomorphic condition of a

reach of a River Style. Reproduced from Fryirs (2003)

with permission from Elsevier, 2003.

Geomorphic

river condition

Good

Moderate

Moderate

Poor



Channel

attributes



Channel

planform



Bed character

































10.6, if a reach of the channelized fill River Style receives 3 out of 4 Yes responses regarding channel

attributes, that degree of freedom is assigned a tick.

In general, however, for a tick to be assigned for a

degree of freedom, most geoindicators must be

considered to be “desirable.” In many instances,

the geoindicators measured within each degree of

freedom are interrelated. For example, shape, size,

and bank morphology are dynamically adjusted

such that a change in one leads to adjustments in

the others. The overall result is a measure of the

condition for that degree of freedom. This assessment provides an indication of how far from the

reference condition the geomorphic structure and

function of different reaches of each River Style

are. The further a reach sits from the reference condition for a certain parameter, the poorer its condition. The observed structure and function of each



Good condition



Moderate condition



Poor condition



Channel

attributes



Compound, stepped cross-sectional form

within a wide, deep incised trench. Bank

erosion minimal. Channel bed dominated by

aquatic swamp vegetation and tussock

grasses. Benches colonized by some hardy

vegetation including Melaleucas.



Compound, stepped cross-sectional form

within a wide, deep, incised trench.

Localized bank erosion and slumping occurs.

Bench units colonized by some hardy

vegetation. Occasional tussock grasses on

sand bars and along the low flow channel.



Large, symmetrical, overwidened incised trench.

Near vertical, exposed banks with significant

erosion along the entire reach. Within-channel

units are unvegetated.



Channel

planform



No lateral adjustment of incised trench.

Swamps and a poorly-defined or

discontinuous channel characterizes the

channel bed. Multiple benches line the

channel margin. Increased within-channel

sedimentation may promote reconnection of

channel and floodplain processes. Scattered

riparian strip. Valley fill surfaces are

dominated by pasture.



Limited planform adjustment of incised

trench. Bench features occur along channel

banks. Well-defined low flow channels shift

over trench floor reworking sand sheets

and bars. Floodplain perched above low

flow channel, disconnecting channel from

floodplain processes. Little or no riparian

strip. Valley fill surfaces are dominated by

pasture.



Incised trench experiencing accelerated rates of

lateral expansion and bed lowering (incision).

Multiple low flow stringers atop sand sheet

produce an array of midchannel and lateral bars.

Floodplain disconnected from the channel given

the incised nature of the fill. No riparian strip.

Valley fill surfaces are dominated by pasture.



Bed character



Segregated sediment mix, with sands in

benches, and mud and organic matter

accumulation on the trench floor. Bed

stable and aggrading in sediment

accumulation reaches.



Moderately segregated sediment mix, with

coarse sands in benches, and finer sand in

the low flow channel. Low flow channel

redistributes and reorganizes sediment

locally within the incised trench, improving

bed material organization. Moderate bed

stability as trench infills. Sand accumulating

on the channel bed. Acting as a sediment

accumulation or transfer zone.



Bedload dominated with limited capacity to retain

finer grained materials. Still releasing sediment

from valley fill. Sediment on the channel bed is

loose, poorly segregated, and poorly sorted. Poor

bed stability. Bed may still be incising. High rates

of material reworking and sediment transport.

Acting as a sediment source zone.



Photograph



Reedy Creek



Wolumla Creek



Anderson Creek (Wolumla tributary)



Chapter 10



Degree of

freedom



318



Table 10.10 Explaining the geomorphic condition of reaches of the channelized fill River Style in Bega catchment. Reproduced from Fryirs (2003) with

permission from Elsevier, 2003.



Table 10.11 Explaining the geomorphic condition of reaches of the partly-confined valley with bedrock-controlled discontinuous floodplain River Style in

Bega catchment (from Fryirs, 2001).

Degree of

freedom



Good condition



Moderate condition



Poor condition



Channel has a relatively low width : depth

ratio, with significant local variability

induced by bedrock outcrops, vegetation, and

woody debris. Natural or low rate of erosion

of concave banks. Cross-sectional form is

asymmetrical on bends and irregular at

inflection points. Islands and bars are

vegetated with hardy shrubs and aquatic

grasses.



Channel has a high width : depth ratio.

Asymmetrical-compound geometry at bend

apices; symmetrical at inflection points.

Localized erosion of concave banks. The

channel has expanded along the reach,

including at inflection points. Point bars and

benches remain largely unvegetated or

dominated by exotics. No woody debris.



Channel has a high width : depth ratio. The channel

is overwidened along the reach, including at

inflection points. Asymmetrical shape at bend

apices, symmetrical shape at inflection points.

Accelerated rates of concave bank erosion and

channel expansion along the entire reach. No

within-channel vegetation or woody debris.



Channel

planform



Low sinuosity, single channel within a

sinuous valley. Moderate lateral stability.

Occasional bedrock outcrops, division of

flow around islands and bank-attached bars

and sand sheets. Bar–island–riffle complexes

are separated by pools. Occasional bank

attached bars and sand sheets. Point

bars and point benches occur on bends.

Discontinuous pockets of floodplain may

be scoured around large trees and shrubs.

Continuous or scattered riparian corridor

consists mainly of natives. Banks are lined

with Lomandra. Point bars are colonized by

tussock. Some hardy shrubs on benches.



Low sinuosity, single channel within a

sinuous valley. Laterally unstable on

concave banks. Point benches, point bars,

concave benches, localized sand sheets,

well-defined low flow channel. Occasional

bedrock outcrops. Discontinuous pockets of

floodplain either scoured or stripped. Poor

riparian vegetation cover. Floodplain

dominated by pasture.



Low sinuosity, single channel within a sinuous

valley. Laterally unstable at concave banks and

inflection points reflecting channel expansion.

Point bars, sand sheets with localized bedrock

outcrops, multistringed low flow channel.

Discontinuous pockets of floodplain either

stripped, characterized by short cutting

floodchannels or extensive sand sheets. No

riparian vegetation. Floodplain dominated by

pasture.



Stage Two of the River Styles framework



Channel

attributes



319



320



Table 10.11 Continued.

Degree of

freedom



Moderate condition



Poor condition



Bed character



Well-segregated bedload, with discrete

pockets of material of different texture.

Some gravel deposits in riffles. Bars and

benches comprise sands, with fine-grained

floodplain. Organic matter accumulation is

high in pools and on the floodplain. Bed is

stable with no signs of incision or

aggradation. High instream roughness

(vegetation and woody debris) promote

localized deposition of fine-grained

materials and organics. Balance maintained

between sediment input and output along

the reach. Acts as a sediment transfer zone.



Poorly sorted material distribution. Sand

sheets present local homogeneity, reducing

roughness and the range of hydraulic

diversity. Bed is unstable with significant

material movement. A balance is maintained

between sediment input and output along

the reach. Acts as a sediment transfer zone.



Near homogeneous sand sheet. Sediment

stored as homogeneous instream and

with a poorly sorted material distribution. Bed is

unstable with significant aggradation and/or

incision occurring. Hydraulically homogeneous.

Reach is sediment transport limited and acts as an

accumulation zone.



Photograph



Upper Tantawangalo Creek



Candelo Creek



Wolumla Creek



Chapter 10



Good condition



Table 10.12 Explaining the geomorphic condition of reaches of the low sinuosity sand bed River Style in Bega catchment (from Fryirs, 2001).

Degree of

freedom



Good condition



Moderate condition



Poor condition



Channel has a relatively low width : depth

ratio with an irregular shape induced by

woody debris and riparian vegetation.

Lomandra lined channel and numerous

aquatic species.



Channel has a compound shape with a

relatively high width : depth ratio (including

each low flow thread). Within-channel ridges

colonized by native shrubs and grasses. Low

flow channels clear of vegetation. No woody

debris.



Channel has a symmetrical shape and a high

width : depth ratio. Channel may be overwidened

and have arelatively homogeneous structure. No

instream vegetation exists.



Channel

planform



Single thread, moderately sinuous aligned

down the centre of the valley. Laterally

stable channel. Continuous floodplains with

backswamps and levees. Localized withinchannel bars, pools and riffles, the

distribution of which is controlled by woody

debris. High channel–floodplain connectivity

maintains backswamps. Occasional drapes

of sand around vegetation on the floodplain.

Densely vegetated riparian zone dominated

by Casuarina cunninghamiana with open

vegetation on the floodplain. Backswamps

contain tussock and are lined with Melaleucas.



Anabranching network of ridges and low flow

channels. Channel expansion and lateral

instability has occurred. Potential for

avulsion into floodplain floodchannels.

Sand sheets characterize the floodplain and

backswamps. Active channel–floodplain

processes maintained. Floodchannels are

active in high flows. Continuous floodplain,

consisting of levees and backswamps.

Complex within-channel and channelmarginal assemblage of units, comprising

benches, sand sheets, midchannel bars,

ridges, etc. Pools are infilled. Good riparian

vegetation coverage, but consists mainly of

exotic vegetation. Backswamps have

aquatic vegetation associations. Floodplain

dominated by pasture.



Low sinuosity, single channel with accelerated

rates of channel expansion. Multiple low flow

channels flow atop sand sheets. Potential for

avulsion into floodchannels. Continuous

floodplain, consisting of levees, backswamps, and

extensive sand sheets. Lateral bars, sand sheets,

shallow runs, and midchannel bars. Pools have

been infilled. Channel–floodplain connectivity is

high, but out-of-balance with extensive sand

sheets over the entire floodplain. Backswamps

are infilling with bedload materials. Little or no

riparian vegetation cover. Floodplain dominated

by pasture.



Stage Two of the River Styles framework



Channel

attributes



321



322



Table 10.12 Continued.

Degree of

freedom



Good condition



Moderate condition



Poor condition



Bed character



Well-segregated material distribution. Mud

and organic matter accumulate in

backswamps. Levees and floodplains

comprise sand and organic accumulations.

Mix of sand and mud instream, with efficient

trapping by bankside vegetation and woody

debris. Bed is stable and hydraulic diversity

is high given the vegetation and woody

debris loading. Acts as a sediment transfer

zone.



Sand-dominated, with occasional

deposition of finer materials around

vegetation on midchannel ridges and on the

floodplain. Bed is stable, but sediment

reorganization is occurring as flow

redistributes sediment into well-defined

islands and ridges. A series of well-defined

low flow channels are formed. Hydraulic

diversity is limited. Acts as a sediment

accumulation zone.



Bed materials dominated by sands forming a

planar homogeneous channel bed. Local

sediment redistribution as multiple low flow

stringers shift over the sand sheets. Bed stability

is low given high rates of sediment accumulation.

Channel is sediment transport limited.



Photograph



No examples exist in Bega catchment



Lower Bega River @ Grevillea



Lower Bega River @ Wolumla Creek



Chapter 10



Stage Two of the River Styles framework

reach places it in a good, moderate, or poor geomorphic condition (Table 10.1).

Three ticks for a reach places it in a good geomorphic condition category (Table 10.9). Reaches

in good geomorphic condition are defined as those

in which river character and behavior are appropriate for the River Style in that valley setting and

that position in the catchment. Geomorphic

structures are in the right place and operating as

expected for that River Style. This reach should

cross-compare closely with the reference condition. Along some of these reaches, the geomorphic

condition may be near-intact.

Three crosses places a reach in the poor condition category (Table 10.9). Poor condition reaches

are defined as those in which river character is divergent from the reference condition and abnormal or accelerated geomorphic behavior/change

occurs. The breaching of a fundamental threshold

could push the reach into a new River Style causing irreversible geomorphic change. Key geomorphic units are located inappropriately along the

reach, and processes are out-of-balance with the

geomorphic structure of the reach. The geomorphic structure of that reach would be given a poor

condition rating compared to the reference reach.

Moderate condition reaches sit between these

two extremes (with either two crosses, or two ticks

for any of the degrees of freedom; Table 10.9).

Certain characteristics of the reach are out-ofbalance or inappropriate for that River Style.

10.4.2 Interpret and explain the geomorphic

condition of the reach

Once the condition of each reach has been determined, a table is constructed for good, moderate,

and poor condition reaches of each River Style in

the catchment that details and explains how each

degree of freedom has adjusted. When tied to the

evolutionary sequences, this allows the causes

rather than the symptoms of change to be identi-



323



fied. Analysis of geomorphic responses to altered

flux boundary conditions and the associated sequence of events that result in changes to geomorphic condition are assessed. These tables provide a

template for repeat surveys, where the geomorphology of the reach can be monitored to determine if improvement has taken place. They also

outline the geomorphic parameters that require

manipulation to improve the condition of the

reach (Tables 10.10–10.12). When completed, a

catchment-wide map showing the condition of

each reach of each River Style is constructed (Plate

10.1).



10.5 Products of Stage Two of the River

Styles framework

A range of products is produced from Stage Two of

the River Styles framework:

• capacity for adjustment table for each River

Style in the catchment;

• table of relevant geoindicators used to determine reference conditions and good, moderate,

and poor condition reaches for each River Style in

the catchment;

• planform and cross-section evolutionary sequences for each River Style noting where irreversible change has occurred;

• tables of “desirability criteria” used to assess the

geomorphic condition of each reach of each River

Style, framed in terms of relevant geoindicators for

each degree of freedom;

• tables noting the “ticks and crosses” for each

reach of each River Style in the catchment, framed

in terms of the three degrees of freedom;

• tables that outline how each degree of freedom

has adjusted along good, moderate, and poor condition reaches of each River Style. Photographs

should accompany these tables;

• a catchment-wide map showing the distribution

of good, moderate, and poor condition reaches.



C H A PT E R 1 1

Stage Three of the River Styles framework:

Prediction of likely future river condition based

on analysis of recovery potential

Restoration is an acid test of our ecological understanding because if we do not understand the

processes at work in an ecosystem we are unlikely to be able to reconstruct it so that it works.

A.D. Bradshaw, 1996, p. 7



11.1 Introduction

Effective management strategies that “work with

nature” must appreciate of the trajectory of change

of the river. For example, if the river was left alone,

would its condition deteriorate or improve?

Notions of geomorphic river recovery encapsulate

a sense of how a river has adjusted from its “natural” condition following human disturbance, and

what that river is adjusting towards. While

changes to river morphology must be considered to

be irreversible (in practical terms) in many river

systems, some rivers have proven to be remarkably

resilient to change, while others have started on a

pathway towards recovery. Recovery is a natural

process that reflects the self-healing capacity of

river systems. In this book, geomorphic river

recovery is defined as the trajectory of change

towards an improved condition. Assessing the

pathway of geomorphic river recovery is a predictive process.

Recovery rarely reflects an orderly, progressive,

and systematic process. Nonlinear dynamics and

threshold-induced responses present considerable

challenges in determining the likelihood that any

particular trajectory will be followed, and when

that will occur. Different components of a system

adjust at different rates, such that different reaches

undergo transitions between different states at different times. Multiple potential trajectories occur

for any given river type dependent on the condition

of each reach and its likely responses to future disturbance events, along with prevailing, system-



specific driving factors and timelags. In the River

Styles framework, three trajectories of change are

determined, namely: degradation, restoration, and

creation (Figure 11.1). On these trajectories, five

different states of adjustment can be differentiated, namely: intact, degraded, turning point,

restored, and created conditions (Table 11.1).

As each River Style operates under a specific set

of boundary conditions and has a distinctive character and behavior, natural recovery processes can

be identified for each River Style. When framed in

terms of its evolution and capacity for adjustment,

this enables prediction of likely future adjustments for each River Style. Assessments of underlying causes and mechanisms of change must

build on solid understanding of river character,

behavior, and downstream patterns, along with

appraisal of geomorphic condition, as outlined

in Stages One and Two of the River Styles

framework.

The route by which a reach has attained its present geomorphic condition has a significant impact

on its future pathway of recovery. Understanding

of past geomorphic change provides a means to explain the timing, rate, and magnitude of change. In

the River Styles framework, reach-based evolutionary timeslices that outline changes to river

character and behavior are analyzed to determine

the stage of adjustment of each reach of each River

Style and predict the likely trajectory of future

change. Assessment of geomorphic river recovery

entails two steps, focusing on the trajectory of

change and analysis of recovery potential (Figure



Stage Three of the River Styles framework



325



Table 11.1 States of adjustment used to describe river recovery.

Term



Definition



River recovery



Trajectory of change towards an improved condition. River recovery is not simply the reverse of river

degradation.

The pathway along which a reach adjusts following disturbance. Three trajectories are identified in the

River Styles framework, degradation, restoration, and creation.

The capacity for improvement in the geomorphic condition of the reach over the next 50–100 years.

Restoration (return to predisturbance condition) or creation (development of a new condition) can

occur. Determining river recovery potential requires an understanding of the linkages of geomorphic

processes, off-site impacts, and limiting factors within a catchment.

A river that has operated in the absence of human disturbance such that the geomorphic characteristics

and behavioral attributes are consistent with the predisturbance state. Reaches are often sufficiently

robust to “bounce back” to their intact condition following disturbances.

A reach that has moved away significantly from its intact condition, and has not commenced along a

recovery pathway. The river continues to adjust to disturbance, and form–process associations are out

of balance.

A transitional stage, used to describe a bifurcation in the reach’s evolution that marks a transition from

degradation to recovery. Future river adjustments may push the river in one of three directions: on the

continuing path of degradation, onto the restoration pathway, or onto the creation pathway. In many

instances, these reaches show initial signs of recovery.

Reversible geomorphic change has occurred and recovery towards a predisturbance state follows

disturbance. Ultimately, these reaches have the potential to regain a near-intact condition.

Recovery towards a new alternative state that did not previously exist at the site. The character and

behavior of these reaches does not equate to a predisturbance state. Rather, the river is adjusting

towards the best attainable state given the prevailing flux boundary conditions. All rivers that have

experienced irreversible geomorphic change are recovering along a creation pathway.



Trajectory of change

Recovery potential



Intact



Degraded



Turning point



Restoration

Creation



11.2). These analyses are a system-specific exercise based on findings from Stages 1 and 2 of the

River Styles framework.

A step-by-step guide with which to derive the

system-specific knowledge that provides a future

focus and predictive capability for river management activities is outlined below.

• Describe and explain the character and behavior

of each reach in the catchment, highlighting the

potential for each reach to adjust its form and

change in response to disturbance events and offsite impacts. Interpret controls on why the reach

looks and behaves the way it does, based on an

understanding of the boundary conditions under

which each reach operates, and interpret the direction and rate of change should any of the boundary

conditions be modified.

• Appraise river evolution to determine the history, pathway, and rate of adjustment of each

reach. Detailed evolutionary frameworks enable

responses to human disturbance to be framed in

light of the longer-term pattern and rate of changes

that reflect the natural capacity for adjustment for



that type of river. If possible, threshold conditions

under which river change occurred should be

isolated. From this, the trajectory of change is appraised, predicting whether the reach will continue to deteriorate, operate as a different type of river

under a modified set of boundary conditions, or

readjust back towards its “intact” state.

• Link all reaches within a catchment and evaluate off-site impacts of disturbance. Assessment of

river recovery potential interprets whether a reach

will recover along a restoration trajectory or a creation trajectory and the relative timeframe over

which this will occur. This is framed in terms of

limiting factors that may inhibit river recovery,

and catchment-specific pressures that will impact

on the future state of the system. An assessment

must be made of how imposed pressures and limiting factors affect different types of rivers at different positions in a catchment, and how these

various responses are linked and interact. This is

completed by examination of the patterns and

rates of physical fluxes (sediment, flow, and vegetation associations), how they have changed over



326



Chapter 11



time, and how they are likely to adjust in the future. This must build on an understanding of the

linkages of geomorphic processes and past/future

changes to their connectivity and coupling that

modify the pattern and rate of propagation of disturbance responses through the system. Barriers

and buffers that bring about lagged responses must



Figure 11.1 The recovery diagram used in the River

Styles framework showing the degradation scale on the

left and the two recovery pathways on the right.

Reprinted from Fryirs and Brierley (2000), with

permission from © V.H. Winston & Son, Inc., All rights

reserved



be interpreted. Geomorphic responses to any given

sequence of natural disturbance events or imposed

pressures are likely to be highly variable, as the

effectiveness of different geomorphic processes is

fashioned by the specific condition of the river at

the time of the event(s). The spatial pattern of river

types in a catchment, along with inherent variability in their sensitivity to disturbance and the

site/reach/catchment specific nature of disturbance events, allow patterns and rates of river

change to be identified and potential off-site impacts to be isolated.

• Integration of these various forms of information is used to determine likely future trajectories

of change. Predictions of future responses to disturbance events should cover a spectrum of future

scenarios based on whether boundary conditions

remain the same or are altered by limiting factors

and pressures.

The inherent diversity, complexity, and uncertainty of natural systems, and human modifications to these systems, ensure that predictions of

future states represent, at best, an approximation

of reality. The precautionary principle must always be applied. Measures of risk or likelihood

that particular future states will be attained should

be provided. In making these “best-guess” predictions, realistic appraisal of contemporary forms,

processes, and condition provides a critical starting place. From this, determinations of various

scenarios for environmental futures can be assessed using foresighting exercises, including appraisals of “what it won’t be like.” The complexity

and differing degree of connectivity of natural systems ensure that geomorphic responses to interference or modification are highly variable. In

some instances, perturbations result in progressive and systematic responses. Elsewhere, complex and/or chaotic responses may be noted. This

makes extrapolation exceedingly difficult. Hence,

the only reasonable outcome is “Know Your

Catchment.”





Figure 11.2 Steps in Stage Three of

the River Styles framework



Stage Three of the River Styles framework



327



Table 11.2 Definition of terms used to describe river recovery potential.

Term



Definition



High recovery

potential

Moderate recovery

potential

Low recovery

potential



Reach is in good geomorphic condition and is located in a position where the potential for deleterious

impacts is minimal. These reaches are commonly found in upstream parts of catchments.

Reach is either resilient to change but in moderate of poor geomorphic condition, or is in good condition,

but sits downstream of a poor condition reach. The potential for off-site impacts and limiting factors

propagating into the reach is high.

Reach is in poor geomorphic condition, is sensitive to change or sits at a position in the catchment where

pressures and limiting factors are likely to have negative off-site impacts that will impact directly on the

future condition of the reach. Often these reaches sit in the most downstream sections of the catchment,

where the cumulative effects of disturbance are manifest.



In the River Styles framework, the direction of

adjustment (i.e., the trajectory) is indicated by determining the most likely future recovery condition. However, it is far more difficult to provide a

quantitative measure of the rate of river recovery.

Hence, river recovery is framed in relative terms,

in which reaches with low recovery potential will

take considerably longer to recover than those

with high recovery potential (Table 11.2).

Quantification of rates of change is a site- or reachspecific endeavour, as reaches of a given River

Style may be at different phases of adjustment to

differing forms of disturbance. In addition, specific

geomorphic properties are unlikely to be uniform

from system to system, as local-scale factors induce differing patterns and rates of adjustment.

The first step in assessment of geomorphic river

recovery is to identify stages of adjustment of each

reach of each River Style. Each reach is placed on

pathways of degradation or recovery and predictions are made about the direction of change. The

geomorphic recovery potential of each reach is determined by assessing the connectivity of reaches

and interpreting limiting factors and pressures. In

Stage Three of the River Styles framework, all

reaches of all River Styles in the catchment are

assessed, and a map of high, moderate, and low

recovery potential reaches is produced.



11.2 Stage Three, Step One: Determine the

trajectory of change

Following disturbance, a reach can adjust along a

creation, restoration, or degradation pathway



(Figure 11.1). The vertical line on the left-hand

side of the recovery diagram represents the continuum from an intact to a fully degraded condition. The contemporary character and behavior

of the reach can lie at any position along this degradation pathway, depending on its geomorphic

condition, its sensitivity to disturbance, the

form and extent of disturbance, and time since

disturbance.

If a natural system is resilient to disturbance, it

operates within its natural capacity for adjustment

and remains close to an intact condition. Ongoing

processes maintain the predisturbance character

and behavior. If human disturbance is severe, such

that a threshold condition is breached, or pervasive

degradation undermines the integrity of the reach,

the river cannot self-adjust, and falls along the

degradation pathway. Such reaches have moved

outside their natural capacity for adjustment.

Reaches in good geomorphic condition sit high on

the degradation pathway, while reaches in poor

geomorphic condition sit low on the degradation

pathway.

Reaches that show initial signs of recovery

are considered to be at the turning point on Figure

11.1. The transition to recovery can occur at any

stage along the sliding scale of the degradation

pathway. The pathways of river adjustment depicted on the right-hand side of Figure 11.1 differentiate between a restoration and a creation trajectory

(Table 11.1). Restoration is defined as a return

towards the characteristic state that reflected predisturbance conditions (Table 11.1). Creation is

defined as recovery towards a new, alternative condition that did not exist previously at the site.



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