rs 5 stages 2 & 3

8/13/2019 RS 5 Stages 2 & 3

http://slidepdf.com/reader/full/rs-5-stages-2-3 1/7

8/11/2013

1

Stages 2 and

3 of

The

River

Styles® Framework

www.riverstyles.com

River condition

What is the present

geomorphic condition of

River XX vs River YY?

River recovery

What is the likelihood of River XX

recovering towards something like

River YY over the next 50‐100 years?

River XX River XX

River YY River YY

Deriving a meaningful procedure to assess

geomorphic river condition

Definition:

• River structure is appropriate for its environmental/landscape setting

• Links to ‘health’ in socio‐ecological terms

Must be:

• Framed in terms of the type of river … Compare like‐with‐like

• Process‐based … Measure relevant parameters for different River

Styles

• Framed in terms of river change (evolution pathway). Identify an

“expected” condition … based on capacity for adjustment under

contemporary catchment boundary conditions

• Compare reaches at different stages of evolutionary adjustment …

determine whether irreversible geomorphic change has occurred

Stage Two: Assessing geomorphic river

condition

Step Two: Identify a reference reach for the River Style

Step One: Interpret river evolution to identify whether change has

been irreversible

Step Three: Determine appropriate measures of geomorphic

condition for that River Style, based upon its capacity for adjustment

Step Four: Relate your reach to the reference reach

Step One:

Interpret

river

evolution

to

identify

whether change has been irreversible

• Assessments of river evolution are used to examine

how the river had adjusted in the past and to explain

how the river is adjusting today (future trajectory is

used to assess river recovery – Stage 3).

• Basis for examining the causes of ‘condition’ rather

than just the symptoms.

• If change has been irreversible – identify reference

reach for the contemporary River Style, not its pre‐

disturbance type.

Step 2: Determine the evolution and natural reference condition

(Confined

valley

with

occ.

fplain.

pockets)

A) 1788

E) future

C) 1890-1944

B) 1840’s

D) today

Natural reference condition

(using evolution)

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Step 2: Determine the evolution and natural reference

condition (Low sinuosity sand bed)

Low sinuosity fine grained Low sinuosity sand bed

Natural reference condition

(using geomorphic insight)

Step Two: Identify a reference reach for the

River Style

Two key concepts:

1)

Determine

what

is

‘natural’

for

that

type

of

river.2) Identify a reference condition (good condition reach) for

that type of river as it is today.

Identify the best available version of the contemporary

River Style against which to compare other reaches.

may be available in the catchment (remnants)

identify them from the evolutionary sequence

use geomorphic insights about how we would expect the river to look and adjust

Step Three: Determine appropriate measures of

geomorphic condition for that River Style, based

upon its capacity for adjustment

• Identify ‘desirability criteria’ based on

parameters that will give a meaningful signal about the condition for a reach.

• Measure parameters that are relevant for the river type under investigation.

• Framed in terms of channel attributes, planform attributes, bed characteristics.

Identification of appropriate measures of river

condition, based upon its behavioural regime and

capacity for adjustment

• Identify appropriate geoindicators and ‘desirability criteria’ based

on parameters that will give a meaningful signal about the

condition for a reach

• Measure parameters that are relevant for the river type under

investigation

• Framed in terms of:

– channel attributes

– planform attributes

– bed characteristics

• Limitations of scoring and weighting schemes: Emphasis here is on

underlying processes (causes)

Confined valley

with

occasional

floodplain pockets River Style

sand bars & sand sheets

vegetated islands

bedrock outcrops

bedrock-induced pool

floodplain

Geoindicator /

River Style

Confined

valley with

occ. fplain

pockets

Channel attributes

Size NO

Shape YES

Bankmorphology

YES

Instream

vegetation

structure

YES

LWD loading YES

River planform

Number of

channels

NO

Sinuosity of

channels

NO

Lateral

stability

NO

Geomorphic

unit

assemblage

YES

Riparian

vegetation

YES

Bed character

Grain size and

sorting

YES

Bed stability NO

Hydraulic

diversity

YES

Sediment

regime

YES

Low sinuosity sand bed River Style in

the laterally

‐unconfined

(continuous)

valley‐setting

Geoindicator /

River Style

Low sinuosity

sand bed

Channel attributes

Size YES

Shape YESBank

morphologyYES

Instream

vegetation

structure

YES

LWD loading YES

River planform

Number of

channels

YES

Sinuosity of

channels

YES

Lateral

stability

YES

Geomorphic

unit

assemblage

YES

Riparian

vegetation

YES

Bed character

Grain size and

sorting

YES

Bed stability YES

Hydraulic

diversity

YES

Sedimentregime

YES

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Step Four: Relate your reach to the reference

reach and explain geomorphic condition

• Relates contemporary

river

condition

to

appropriate (expected) measures (e.g. reference reach)

• Highlights how far from a ‘good’ condition the

reach has adjusted, and which attributes are

not functioning appropriately

• Explains the causes not the symptoms of change

Reaches in a good condition

• River character

and

behaviour

are

appropriate

for

the River Style, given its valley‐setting and within‐

catchment position

• Native riparian vegetation associations occur

• Answer yes to all the desirability criteria

Reaches in a moderate condition

• Locally, geomorphic structures are in the wrong

places and there are some anomalous processes

and/or vegetation associations

• Answer yes

to

most

of

the

desirability

criteria

Reaches in a poor condition

• Answer no to all of the desirability criteria

• Geomorphic process‐form associations are

‘inappropriate’ for that setting (either character‐

behaviour, extent, or rate of process activity

(accelerated or suppressed))

• Vegetation associations are ‘inappropriate’ for that

setting

Example 1: Channelised fill River Style

Good

Moderate

Poor

Good Moderate Poor

Example 2: Confined valley with occ. fp. pockets River Style

Good

Moderate

Poor

Good Moderate Poor

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Catchment

condition map(Bega catchment)

Brogo Dam

Good condition reaches

Moderate condition reaches

Poor condition reaches

BEGA

Bega

Creek

Creek

SouthWolumla

Selecting appropriate indicators of geomorphic

river condition

• Channel attributes (size, shape, bank morphology, riparian vegetation)

• Planform attributes (number of channels, sinuosity, lateral stability, geomorphic

unit assemblage)

• Bed characteristics (grain size, sorting, bed stability, hydraulic diversity)

Laterally‐unconfined

valley

Anastomosing river

Partly‐confined valley with

bedrock‐controlled

discontinuous floodplain

Confined

Valley:

Gorge

Laterally unconfined

valley

Braided river

Laterally unconfined

valley

Active meandering

river (sand bed)

Laterally‐unconfined

valley

Upland swamp

Stage Three of the River Styles

Framework: Assessing the evolutionary

trajectory and geomorphic recovery

potential of rivers

• River recovery determines the trajectory of

change a reach is likely to take (3 pathways:

degradation,

creation

and

restoration).

• Determines the potential for a reach to move

towards a restored or created condition.

River condition

What is the present

geomorphic condition of

River XX vs River YY?

River recovery

What is the likelihood of River XX

recovering towards something like

River YY over the next 50‐100 years?

River XX River XX

River YY River YY

Stage Three:

Assessing

geomorphic

river

recovery potential

Step One: Determine the trajectory of river change over

the next 50‐100 years

Step Two: Assess river recovery potential … place each

reach in its catchment context and assess

limiting factors to recovery

Assessing

geomorphic

adjustments

at

the

catchment scale

• River diversity (and capacity for adjustment) at the reach

scale

• Process‐based understanding (how/why the river adjusts in

the way that it does)

• River patterns within any given catchment (downstream

patterns, connectivity, tributary‐trunk stream relationships)

• Changes to boundary conditions and flow‐sediment

relationships over time

– Evolutionary trajectory

– Responses to human disturbance

8/13/2019 RS 5 Stages 2 & 3


8/13/2019 RS 5 Stages 2 & 3


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Turning point

Degraded

Intact

Restored

Created

The recovery

diagram

IntactRestoredcondition

Degraded

Createdcondition

Turning points

Evolutionary trajectory:

reversible or irreversible

change

What do you measure against?

Trajectory of change

• Framed in

terms

of

evolutionary

trends

– if irreversible change has occurred ‐ only

creation is possible

– if reversible change has occurred ‐ creation

and/or restoration is possible

Step One: Determining the trajectory of change of a

reach … positioning reaches on the recovery diagram

Has the river started to recover?

Turningpoint

Degraded

Is the reach intact?Intact

Is restoration possible?

Restoration

Creation

Is the reach adopting anew condition?

YESYES

YESYES

YESYES

YESYES

NONO NONO

YESYES

NONO

IntactRestoredcondition

Degraded

Createdcondition

Turning poin ts

Trajectories

of change

for reaches

of a

bedrock‐

controlled

discont.

Floodplain

River Style

Intact

CreatedCondition

Turning Points

RestoredCondition

Degraded

A

B

D

A

B

D

C

C

E

E

F F

G

G

Step Two: Assessing river recovery potential

• Determine what is achievable for any given catchment

– Recognize that in some instances we have lost the capacity for recovery

(new/novel ecosystems)

– Address issues of concern/significance where we can make a difference

• Catchment‐specific assessment based on linkages of reaches in

the catchment

• Based on mix of river sensitivity, condition and position in

catchment for each reach (i.e. the effect of limiting factors)

• Assess pressures and limiting factors to recovery

– Pressures: land use change, climate change, water management programs,

etc

– Limiting factors: sediment transfer, flow regime, nutrient fluxes, weed

infestations, seed sources, etc

Future focus:

Scenario

building

What happens if sediment supply remains as is? What happens if sediment supply is reduced?

What happens if sediment supply is increased?

Modelling applications tied to real world data

8/13/2019 RS 5 Stages 2 & 3


rs 5 stages 2 & 3

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