Geomorphology and River Management E-Book

Gary J. Brierley

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 855

Veröffentlichungsjahr: 2013

Beschreibung

This book outlines a generic set of procedures, termed the River Styles Framework, which provides a set of tools for interpreting river character, behavior, condition, and recovery potential. Applications of the framework generate a coherent package of geomorphic information, providing a physical template for river rehabilitation activities.

• management and restoration of rivers is a rapidly growing topic for environmental scientists, geologists and ecologists - this book provides a learning tool with which to approach geomorphic applications to river management
  
• describes the essential geomorphological principles underlying river behaviour and evolution
  
• demonstrates how the River Styles Framework can turn geomorphic theory into practice, to develop workable strategies for restoration and management
  
• based on real case studies and authors extensive experience
  
• applicable to river systems worldwide
  
• synthesises fluvial geomorphology, ecology and management

Leseprobe

Contents

Preface

Acknowledgments

CHAPTER 1 Introduction

1.1 Concern for river health

1.2 Geomorphic perspectives on ecosystem approaches to river management

1.3 What is river restoration?

1.4 Determination of realistic goals in river rehabilitation practice

1.5 Managing river recovery processes in river rehabilitation practice

1.6 Overview of the River Styles framework

1.7 Layout and structure of the book

PART A The geoecological basis of river management

CHAPTER 2 Spatial considerations in aquatic ecosystem management

2.1 Introduction and chapter structure

2.2 Spatial scales of analysis in aquatic geoecology: A nested hierarchical approach

2.3 Use of geomorphology as an integrative physical template for river management activities

2.4 Working with linkages of biophysical processes

2.5 Respect diversity

2.6 Summary

CHAPTER 3 Temporal considerations in aquatic ecosystem management

3.1 Chapter structure

3.2 Working with river change

3.3 Timescales of river adjustment

3.4 Interpreting controls on river character and behavior

3.5 Predicting the future in fluvial geomorphology

3.6 Summary and implications

PART B Geomorphic considerations for river management

CHAPTER 4 River character

4.1 Introduction: Geomorphic approaches to river characterization

4.2 Channel bed morphology

4.3 Bank morphology

4.4 Channel morphology: Putting the bed and banks together

4.5 Channel size

4.6 Floodplain forms and processes

4.7 Channel planform

4.8 Valley confinement as a determinant of river morphology

4.9 Synthesis

CHAPTER 5 River behavior

5.1 Introduction: An approach to interpreting river behavior

5.2 Ways in which rivers can adjust: The natural capacity for adjustment

5.3 Construction of the river evolution diagram

5.4 Bed mobility and bedform development

5.5 Adjustments to channel shape

5.6 Interpreting channel behavior through analysis of insteam geomorphic units

5.7 Adjustments to channel position on the valley floor

5.8 Use of geomorphic units as a unifying attribute to assess river behavior

5.9 Synthesis

CHAPTER 6 River change

6.1 Introduction

6.2 Framing river evolution in context of Late Quaternary climate change

6.3 The nature of river change

6.4 Framing river change on the river evolution diagram

6.5 The spatial distribution of river change

6.6 Temporal perspectives of river change

6.7 Appraising system vulnerability to change

CHAPTER 7 Geomorphic responses of rivers to human disturbance

7.1 Introduction: Direct and indirect forms of human disturbance to rivers

7.2 Direct human-induced changes to river forms and processes

7.3 Indirect river responses to human disturbance

7.4 Spatial and temporal variability of human impacts on rivers

7.5 (Ir)reversibility and the river evolution diagram revisited

7.6 Synopsis

PART C The River Styles framework

CHAPTER 8 Overview of the River Styles framework and practical considerations for its application

8.1 Moves towards a more integrative river classification scheme

8.2 What is the River Styles framework?

8.3 Scale and resolution in practical application of the River Styles framework

8.4 Reservations in use of the River Styles framework

CHAPTER 9 Stage One of the River Styles framework: Catchment-wide baseline survey of river character and behavior

9.1 Introduction

9.2 Stage One, Step One: Regional and catchment setting analyses

9.3 Stage One, Step Two: Definition and interpretation of River Styles

9.4 Stage One, Step Three: Assess controls on the character, behavior, and downstream patterns of River Styles

9.5 Overview of Stage One of the River Styles framework

CHAPTER 10 Stage Two of the River Styles framework: Catchment-framed assessment of river evolution and geomorphic condition

10.1 Introduction

10.2 Stage Two, Step One: Determine the capacity for adjustment of the River Style

10.3 Stage Two, Step Two: Interpret river evolution to assess whether irreversible geomorphic change has occurred and identify an appropriate reference condition

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

10.5 Products of Stage Two of the River Styles framework

CHAPTER 11 Stage Three of the River Styles framework: Prediction of likely future river condition based on analysis of recovery potential

11.1 Introduction

11.2 Stage Three, Step One: Determine the trajectory of change

11.3 Stage Three, Step Two: Assess river recovery potential: Place reaches in their catchment context and assess limiting factors to recovery

11.4 Products of Stage Three of the River Styles framework

CHAPTER 12 Stage Four of the Rivers Styles framework: Implications for river management

12.1 Introduction: River rehabilitation in the context of river recovery

12.2 Stage Four, Step One: Develop a catchment-framed physical vision

12.3 Stage Four, Step Two: Identify target conditions for river rehabilitation and determine the level of intervention required

12.4 Stage Four, Step Three: Prioritize efforts based on geomorphic condition and recovery potential

12.5 Stage Four, Step Four: Monitor and audit improvement in geomorphic river condition

12.6 Products of Stage Four of the River Styles framework

CHAPTER 13 Putting geomorphic principles into practice

13.1 Introduction

13.2 Geomorphology and environmental science

13.3 Geomorphology and river management: Reading the landscape to deveop practices that work with river diversity and dynamism

13.4 The river management arena

13.5 Use of the River Styles framework in geomorphology and river management

References

Index

To our families

“Every tool carries with it the spirit by which it has been created.”

Werner Karl Heisenberg

© 2005 by Blackwell Publishing

BLACKWELL PUBLISHING

350 Main Street, Malden, MA 02148-5020, USA

9600 Garsington Road, Oxford OX4 2DQ, UK

550 Swanston Street, Carlton, Victoria 3053, Australia

The right of Gary J. Brierley and Kirstie A. Fryirs to be identified as the Authors of this Work has been asserted in accordance with the UK Copyright, Designs, and Patents Act 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs, and Patents Act 1988, without the prior permission of the publisher.

First published 2005 by Blackwell Science Ltd

2 2006

Library of Congress Cataloging-in-Publication Data

Brierley, Gary J.

Geomorphology and river management: applications of the river styles framework/Gary J. Brierley and Kirstie A. Fryirs.

p. cm.

Includes bibliographical references and index.

ISBN 1-4051-1516-5 (pbk.: alk. paper) 1. Rivers. 2. Stream ecology. 3. Watershed management.

4. Geomorphology. I. Fryirs, Kirstie A. II. Title.

GB1203.2.B755 2005

551.48’3 – dc22

2004011686

ISBN-13: 978-1-4051-1516-2

A catalogue record for this title is available from the British Library.

For further information on

Blackwell Publishing, visit our website:

www.blackwellpublishing.com

Preface: our personal, Australian, perspectives

Every country has its own landscape which deposits itself in layers on the consciousness of its citizens, thereby canceling the exclusive claims made by all other landscapes.

Murray Bail, 1998, p. 23

Any book reflects the personal histories and associated geographic and cultural values of its authors. In a number of ways it is increasingly difficult for us to separate our scientific perspective on rivers and their management from an emotional and aesthetic bond that has developed in our work. Working within a conservation ethos, we promote a positive sense of what can be achieved through effective implementation of rehabilitation practices.

Perspectives conveyed in this book undoubtedly reflect, to some degree, the distinctive nature of the Australian landscape and biota, the recent yet profound nature of disturbance associated with colonial settlement, and community involvement in river conservation and rehabilitation practices. The long and slow landscape evolution of the Australia landmass has resulted in rivers with a distinctive character and behavior, driven by factors such as the relative tectonic stability and topographic setting of the continent, pronounced discharge variability, and limited material availability. Remarkably few river systems comprise truly alluvial, self-adjusting streams. Many contemporary river forms and processes have been influenced by antecedent landscape controls, such as the nature of the bedrock or older alluvial materials over which they flow, and generally limited relief. Given the nature of the environmental setting, it is scarcely surprising that the Australian landscape is characterized by an array of river forms and processes that is seldom observed elsewhere. Across much of the continent, human disturbance has left a profound “recent” imprint on this largely ancient landscape, the consequences of which vary markedly from system to system (e.g. Rutherfurd, 2000).

Along with its unique environmental setting and history of human disturbance, a distinctive approach to natural resources management that is characterized by extensive on-the-ground involvement of community groups has developed in Australia. Rehabilitation strategies implemented through Catchment Management Committees (or Authorities/Trusts), Landcare Groups, Rivercare Groups, etc. have been complemented by core support through Federal and State Government programs. Adoption of participatory rather than regulatory approaches to river management has presented significant opportunity to incorporate research ideas into management practice.

Uptake of rehabilitation programs that strive to heal river systems in Australia has been driven by extensive involvement and leadership from the small group of professional geomorphologists in the country. A significant collection of tools and techniques for river rehabilitation has been provided, including the National Stream Rehabilitation Guide (Rutherfurd et al., 2000), the National Stream Restoration Framework (Koehn et al., 2001), and proceedings from various Stream Management Conferences (Rutherfurd and Walker, 1996; Rutherfurd and Bartley, 1999; Rutherfurd et al., 2001b). Our efforts in writing this book have been aided enormously by this invigorating set of research products, and the dedication of various river practitioners who have “made this happen.”

In our quest to develop a logical set of principles with which to interpret the diversity and complexity of the real world, we have tried to communicate our understanding in as simple a way as possible. Duplications, inaccuracies, and inconsistencies may have arisen in cross-disciplinary use of terms, but hopefully we provide a useful platform that aids uptake and implementation of geomorphic principles in river rehabilitation practice.

Although this book has an unashamedly Australian flavor, we have endeavored to write it from a global perspective. We convey our apologies, in advance, to those readers to whom this book bears little semblance of reality in terms of the types of rivers you live and/or work with. However, we hope that the principles presented here bear relevance to the management issues that you face, and that the book provides useful guidance in the development of core understanding that is required if management activities are to yield sustainable outcomes.

Acknowledgments

The River Styles framework has its origins in river reach analysis of the Waiau River in New Zealand, in a project coordinated through Southland Regional Council, following a flash of inspiration generated by Glen Lauder. In 1994, Gary Brierley was invited to South Africa to participate in a river health workshop coordinated by Barry Hart (from the Australian half of the gathering). This built on initial contacts suggested by Brian Finlayson, who recommended an approach be made to a Federal Government body, the Land and Water Resources Research and Development Corporation (now Land and Water Australia; LWA) to seek support to continue this work. The award of a substantive grant effectively marked the birth of the River Styles framework. Phil Price provided invaluable guidance in these initial endeavors – his broadening of scope ensured that a generic, open-ended approach was developed, moving beyond a case study perspective. Further backing by Siwan Lovett and Nick Schofield in LWA aided the coordination of early work. Collaboration with Tim Cohen, Sharon Cunial, and Fiona Nagel fashioned initial endeavors, with willing sounding boards on hand at Macquarie University in discussions with Andrew Brooks, John Jansen, and Rob Ferguson.

Substantive external support through the State Government agency, then called the Department of Land and Water Conservation (DLWC), was generated at the outset of the project. Head Office leadership was guided by David Outhet, and on the-ground support in the Bega Regional Office, initially by Justin Gouvernet and Don McPhee and substantially with Cliff Massey. The practical development and application of the River Styles work in Bega catchment was enormously enhanced by collaboration with the former Far South Coast Catchment Management Committee, under leadership by Kerry Pfeiffer and funding generated through the Bega Valley Shire and the Natural Heritage Trust (NHT). Various workshops and reports promoted early findings of the work. At one of these meetings, Michael Pitt and various colleagues from the North Coast Office of DLWC envisaged potential applications of equivalent work in their catchments. Tony Broderick played a pivotal part in facilitating these applications. At this stage, Rob Ferguson, Ivars Reinfelds, and Guy Lampert extended the range of rivers to which the work was applied through characterizations of rivers in the Manning catchment. The primary role of differing forms of valley confinement, which formed a part of the PhD work completed by Rob Ferguson, advanced the framework.

Subsequent developments included research on stream power along longitudinal profiles in the Bellinger catchment, in work completed with Tim Cohen and Ivars Reinfelds. Insights into geological controls on patterns of River Styles was provided by Geoff Goldrick, in application of this work in the Richmond catchment. Eventually more than 10 catchment-based reports characterized the diversity of River Styles and their downstream patterns, in all North Coast catchments extending from the Hastings to the Tweed. Rob Ferguson coordinated this work, with field work completed by Guy Lampert. Paul Batten provided the initial algorithms to generate longitudinal profiles and stream power plots through use of Geographic Information Systems and Digital Elevation Models. Paula Crighton was invaluable in refining this procedure and processing the data for the North Coast catchments. Practical application of the work was enhanced through a subsequent contract in the Shoalhaven catchment where Rachel Nanson completed much of the field work.

A major advancement in the development of the River Styles framework occurred with extensions from assessment of river character and behavior to analyses of river condition and recovery potential. The PhD work of Kirstie Fryirs developed these procedures and applied them in the Bega catchment. These procedures now form Stages 2 and 3 of the framework. The development of these procedures was enhanced by a visit to Australia by Scott Babakaiff (funded by LWA) and development of the National River Restoration Framework (in a project with John Koehn and Belinda Cant funded by LWA).

The next phase of the River Styles work entailed fundamental research into ecological (habitat) associations with a geomorphic classification scheme. This work was completed by two Post-Docs (Mark Taylor and Jim Thomson), through collaborative funding provided by LWA and DLWC. Penny Knights and Glenda Orr supported this work. Collaboration with Bruce Chessman linked geomorphology and ecology in assessments of geoecological condition in Bega catchment.

Since its creation, promotion and adoption of the River Styles framework has occurred across the nation. Particular mention must be made of David Outhet, who promoted the adoption of the framework as a tool for management activities in New South Wales, and provided numerous insightful comments on its application. Sally Boon in Queensland and David Wright in Tasmania have also promoted the framework and have sourced funding for us to run courses and workshops in those states.

Numerous members of the Rivers Group at Macquarie University have provided many hours of enthusiastic and fruitful discussion about rivers. While most now roam further afield, they remain a large part of the“history”associated with this book. Particular mention must be made of Andrew Brooks, Tim Cohen, Rob Ferguson, John Jansen, Emily Cracknell, Paula Crighton, Mick Hillman, Pete Johnston, and Kahli McNab. Mick Hillman, in particular, provided the stimulus for greatly enhancing the ‘extension science’ component of our work.

Insightful and constructive review comments on this book were made by a range of academics and postgraduate students, including Ted Hickin, Malcolm Newson, Jonathan Phillips, Rob Ferguson, Jo Hoyle, Nick Preston, and John Spencer. These review comments substantially improved the clarity and communicability of the book.

Teaching River Styles Short Courses has occurred in parallel to development of the framework. We wish to thank the participants of these courses, who have spanned a wide range of professions and levels of experience from around the nation and overseas. Their contributions have improved the presentation of the River Styles framework and our ability to communicate and teach it. Each River Styles Short Course has been run through Macquarie Research Limited (MRL) with administrative support from Roslyn Green, Kerry Tilbrook, and Sophie Beauvais. Sophie Beauvais, Irina Zakoshanski, and Warren Bailey are thanked for their support in administering developments of the framework, promotion, trade-marking, and accreditation of the framework. The term River Styles® is a registered trademark held by Macquarie University and Land and Water Australia.

Most of the graphics in this book were designed by Kirstie Fryirs and drafted by Dean Oliver Graphics, Pty Ltd. We thank Dean for his commitment to this project. We also thank colleagues in the Department of Physical Geography, Macquarie University for their support.

Sincere thanks to Sue and Paul Gebauer who own Wonga Wildlife Retreat in Coffs Harbour. They provided us with a writer’s paradise. Without Wonga the book would not be what it is today. We also extend our thanks to Chris and Rick Fryirs for use of their Woodford house during the postreview stage.

We extend our love to our families for their patience and support over the many years it has taken to write this book; Emmy, Zac, Whit, Chris, Rick, Steve, Sarah, Tim, Dee, Chris – thank you!

Self-evidently, many people have helped us along the way in a process that has provided many intellectual and personal challenges. Their insight and support have encouraged us to “maintain the rage,” during countless phases when the project didn’t quite want to come to fruition. Indeed, we hope the book is far from an endpoint. As in any book, ultimate responsibility in ideas presented lie with the authors. Our apologies, in advance, to anyone whose thoughts have been misrepresented.

CHAPTER 1

Introduction

Society’s ability to maintain and restore the integrity of aquatic ecosystems requires that conservation and management actions be firmly grounded in scientific understanding.

LeRoy Poff, et al., 1997, p. 769

1.1 Concern for river health

Rivers are a much-cherished feature of the natural world. They perform countless vital functions in both societal and ecosystem terms, including personal water consumption, health and sanitation needs, agricultural, navigational, and industrial uses, and various aesthetic, cultural, spiritual, and recreational associations. In many parts of the world, human-induced degradation has profoundly altered the natural functioning of river systems. Sustained abuse has resulted in significant alarm for river health, defined as the ability of a river and its associated ecosystem to perform its natural functions. In a sense, river health is a measure of catchment health, which in turn provides an indication of environmental and societal health. It is increasingly recognized that ecosystem health is integral to human health and unless healthy rivers are maintained through ecologically sustainable practices, societal, cultural, and economic values are threatened and potentially compromised. Viewed in this way, our efforts to sustain healthy, living rivers provide a measure of societal health and our governance of the planet on which we live. It is scarcely surprising that concerns for river condition have been at the forefront of conservation and environmental movements across much of the planet.

In the past, the quest for security and stability to meet human needs largely overlooked the needs of aquatic ecosystems. In many instances, human activities brought about a suite of unintended and largely unconsidered impacts on river health, compromising the natural variability of rivers, their structural integrity and complexity, and the maintenance of functioning aquatic ecosystems. Issues such as habitat loss, degradation, and fragmentation have resulted in significant concerns for ecological integrity, sustainability, and ecosystem health. As awareness and understanding of these issues has improved, society no longer has an excuse not to address concerns brought about by the impacts of human activities on river systems. Shifts in environmental attitudes and practice have transformed outlooks and actions towards revival of aquatic ecosystems. Increasingly, management activities work in harmony with natural processes in an emerging “age of repair,” in which contemporary management strategies aim to enhance fluvial environments either by returning rivers, to some degree, to their former character, or by establishing a new, yet functional environment. Notable improvements to river health have been achieved across much of the industrialized world in recent decades. However, significant community and political concern remains over issues such as flow regulation, algal blooms, salinity, loss of habitat and species diversity, erosion and sedimentation problems, and water resource overallocation.

Rivers demonstrate a remarkable diversity of landform patterns, as shown in Figure 1.1. Each of the rivers shown has a distinct set of landforms and its own behavioral regime. Some rivers have significant capacity to adjust their form (e.g., the meandering, anastomosing, and braided river types), while others have a relatively simple geomorphic structure and limited capacity to adjust (e.g., the chain-of-ponds and gorge river types). This variability in geomorphic structure and capacity to adjust, which reflects the array of landscape settings in which these rivers are found, presents significant diversity in the physical template atop which ecological associations have evolved.

Figure 1.1 The diversity of river morphologyRivers are characterized by a continuum of morphological diversity, ranging from bedrock controlled variants such as (a) gorges (with imposed sets of landforms), to fully alluvial, self-adjusting rivers such as (c) braided and (d) meandering variants (with various midchannel, bank-attached and floodplain features). Other variants include multichanneled anastomosing rivers that form in wide, low relief plains (e), and rivers with discontinuous floodplain pockets in partly-confined valleys (b). In some settings, channels are discontinuous or absent, as exemplified by chain-of-ponds (f). Each river type has a different capacity to adjust its position on the valley floor. (a) Upper Shoalhaven catchment, New South Wales, Australia, (b) Clarence River, New South Wales, Australia, (c) Rakaia River, New Zealand, (d) British Columbia, Canada, (e) Cooper Creek, central Australia, and (f) Murrumbateman Creek, New South Wales, Australia.

Developing a meaningful framework to recognize, understand, document, and maintain this geodiversity is a core theme of this book. Working within a conservation ethos, emphasis is placed on the need to maintain the inherent diversity of riverscapes and their associated ecological values. Adhering to the precautionary principle, the highest priority in management efforts is placed on looking after good condition remnants of river courses, and seeking to sustain rare or unique reaches of river regardless of their condition.

Just as there is remarkable diversity of river forms and processes in the natural world, so human-induced disturbance to rivers is equally variable (see Figure 1.2). Many of these actions have been intentional, such as dam construction, channelization, urbanization, and gravel or sand extraction. Far more pervasive, however, have been inadvertent changes brought about through adjustments to flow and sediment transfer regimes associated with land-use changes, clearance of riparian vegetation, etc. Across much of the planet, remarkably few river systems even approximate their pristine condition. Most rivers now operate as part of highly modified landscapes in which human activities are dominant.

Figure 1.2 Human modifications to river coursesHuman modifications to rivers include (a) dams (Itaipu Dam, Brazil), (b) channelization (Ishikari River, Japan), (c) urban stream (Cessnock, New South Wales, Australia), (d) native and exotic vegetation removal (Busby’s Creek, Tasmania, Australia), (e) gravel and sand extraction (Nambucca River, New South Wales, Australia), and (f) mine effluent (King River, Tasmania, Australia).

The innate diversity of river courses is a source of inspiration, but it presents many perplexing challenges in the design and implementation of sustainable management practices. Unless management programs respect the inherent diversity of the natural world, are based on an understanding of controls on the nature and rate of landscape change, and consider how alterations to one part of an ecosystem affect other parts of that system, efforts to improve environmental condition are likely to be compromised. River management programs that work with natural processes will likely yield the most effective outcomes, in environmental, societal, and economic terms. Striving to meet these challenges, truly multifunctional, holistic, catchment-scale river management programs have emerged in recent decades (e.g., Gardiner, 1988; Newson, 1992a; Hillman and Brierley, in press). Procedures outlined in this book can be used to determine realistic goals for river restoration and rehabilitation programs, recognizing the constraints imposed by the nature and condition of river systems and the cultural, institutional, and legal frameworks within which these practices must be applied.

1.2 Geomorphic perspectives on ecosystem approaches to river management

Rivers are continuously changing ecosystems that interact with the surrounding atmosphere (climatic and hydrological factors), biosphere (biotic factors), and earth (terrestrial or geological factors). Increasing recognition that ecosystems are open, nondeterministic, heterogeneous, and often in nonequilibrium states, is prompting a shift in management away from maintaining stable systems for particular species to a whole-of-system approach which emphasizes diversity and flux across temporal and spatial scales (Rogers, 2002). Working within an ecosystem approach to natural resources management, river rehabilitation programs apply multidisciplinary thinking to address concerns for biodiversity and ecosystem integrity (Sparks, 1995). Inevitably, the ultimate goals of these applications are guided by attempts to balance social, economic, and environmental needs, and they are constrained by the existing hydrological, water quality, and sediment transport regimes of any given system (Petts, 1996). Ultimately, however, biophysical considerations constrain what can be achieved in river management. If river structure and function are undermined, such that the ecological integrity of a river is compromised, what is left? River rehabilitation programs framed in terms of ecological integrity must build on principles of landscape ecology. The landscape context, manifest through the geomorphic structure and function of river systems, provides a coherent template upon which these aspirations must be grounded. The challenge presented to geomorphologists is to construct a framework with which to meaningfully describe, explain, and predict the character and behavior of aquatic ecosystems.

Biological integrity refers to a system’s wholeness, including presence of all appropriate biotic elements and occurrence of all processes and interactions at appropriate scales and rates (Angermeier and Karr, 1994). This records a system’s ability to generate and maintain adaptive biotic elements through natural evolutionary processes. Ecosystem integrity requires the maintenance of both physico-chemical and biological integrity, maintaining an appropriate level of connectivity between hydrological, geomorphic, and biotic processes. While loss of biological diversity is tragic, loss of biological integrity includes loss of diversity and breakdown in the processes necessary to generate future diversity (Angermeier and Karr, 1994). Endeavors to protect ecological integrity require increased reliance on preventive rather than reactive management, and a focus on landscapes rather than populations.

In riparian landscapes, aquatic, amphibious, and terrestrial species have adapted to a shifting mosaic of habitats, exploiting the heterogeneity that results from natural disturbance regimes (Junk et al., 1989; Petts and Amoros, 1996; Naiman and Decamps, 1997; Ward et al., 2002). This mosaic includes surface waters, alluvial aquifers, riparian vegetation associations, and geomorphic features (Tockner et al., 2002). Because different organisms have different movement capacities and different habitat ranges, their responses to landscape heterogeneity differ (Wiens, 2002). Fish diversity, for example, may peak in highly connected habitats, whereas amphibian diversity tends to be highest in habitats with low connectivity (Tockner et al., 1998). Other groups attain maximum species richness between these two extremes. The resulting pattern is a series of overlapping species diversity peaks along the connectivity gradient (Ward et al., 2002). Given the mutual interactions among species at differing levels in the food chain, ecosystem functioning reflects the range of habitats in any one setting and their connectivity.

Landscape ecology examines the influence of spatial pattern on ecological processes, considering the ecological consequences of where things are located in space, where they are relative to other things, and how these relationships and their consequences are contingent on the characteristics of the surrounding landscape mosaic. The pattern of a landscape is derived from its composition (the kinds of elements it contains), its structure (how they are arranged in space), and its behavior (how it adjusts over time; Wiens, 2002). A landscape approach to analysis of aquatic ecosystems offers an appropriate framework to elucidate the links between pattern and process across scales, to integrate spatial and temporal phenomena, to quantify fluxes of matter and energy across environmental gradients, to study complex phenomena such as succession, connectivity, biodiversity, and disturbance, and to link research with management (Townsend, 1996; Tockner et al., 2002; Ward et al., 2002; Wiens, 2002).

Principles from fluvial geomorphology provide a physical template with which to ground landscape perspectives that underpin the ecological integrity of river systems. Although landscape forms and processes, in themselves, cannot address all concerns for ecological sustainability and biodiversity management, these concerns cannot be meaningfully managed independent from geomorphological considerations. Working from the premise that concerns for ecological integrity are the cornerstone of river management practice, and that landscape considerations underpin these endeavors, interpretation of the diversity, patterns, and changing nature of river character and behavior across a catchment is integral to proactive river management. This book outlines a generic set of procedures by which this understanding can be achieved.

Rehabilitation activities must be realistically achievable. Most riverscapes have deviated some way from their pristine, predisturbance condition. Hence, practical management must appraise what is the best that can be achieved to improve the health of a system, given the prevailing boundary conditions under which it operates. In instances where human changes to river ecosystems are irreversible or only partially reversible, a pragmatic definition of ecological integrity refers to the maintenance of a best achievable condition that contains the community structure and function that is characteristic of a particular locale, or a condition that is deemed satisfactory to society (Cairns, 1995). Specification of the goals of river management, in general, and river restoration, in particular, has provoked considerable discussion, as highlighted in the following section.

1.3 What is river restoration?

The nature and extent of river responses to human disturbance, and the future trajectory of change, constrain what can realistically be achieved in river management (Figure 1.3; Boon, 1992). At one extreme, conservation goals reflect the desire to preserve remnants of natural or near-intact systems. Far more common, however, are endeavors to rectify and repair some (or all) of the damage to river ecosystems brought about by human activities. Various terms used to describe these goals and activities can be summarized using the umbrella term “restoration.”

Restoration means different things to different people, the specific details of which may promote considerable debate and frustration (Hobbs and Norton, 1996). Although the term has been applied to a wide range of management processes/activities, its precise meaning entails the uptake of measures to return the structure and function of a system to a previous state (an unimpaired, pristine, or healthy condition), such that previous attributes and/or values are regained (Bradshaw, 1996; Higgs, 2003). In general, reference is made to predisturbance functions and related physical, chemical, and biological characteristics (e.g., Cairns, 1991; Jackson et al., 1995; Middleton, 1999).

Figure 1.3 Framing realistic management options – what can be realistically achieved?Determination of river rehabilitation goals is constrained primarily by what it is realistically possible to achieve. This reflects system responses to human disturbance, the prevailing set of boundary conditions, and the likely future trajectory of change (as determined by limiting factors and pressures operating within the catchment and societal goals). Maintenance of an intact condition is a conservation goal. If a return to a predisturbance state is possible and desirable, rehabilitation activities can apply recovery principles to work towards a restoration goal. In many instances, adoption of a creation goal, which refers to a new condition that previously did not exist at the site, is the only realistic option.

The few studies that have documented geomorphic attributes of relatively intact or notionally pristine rivers (e.g., Collins and Montgomery, 2001; Brooks and Brierley, 2002), and countless studies that have provided detailed reconstructions of river evolution over timescales of decades, centuries, or longer, indicate just how profound human-induced changes to river forms and processes have been across most of the planet. It is important to remember the nonrepresentative nature of the quirks of history that have avoided the profound imprint of human disturbance. Intact reaches typically lie in relatively inaccessible areas. They are seldom representative of the areas in which management efforts aim to improve river health. However, it is in these reaches, and adjacent good condition reaches, that efforts at restoration can meaningfully endeavor to attain something akin to the pure definition of the word.

Viewed in a more general sense, restoration refers to a management process that provides a means to communicate notions of ecosystem recovery (Higgs, 2003). For example, the Society for Ecological Restoration (SERI, 2002) state that restoration refers to the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed. The notion of recovery describes the process of bringing something back.

Endeavors that assist a system to adjust towards a less stressed state, such that there is an improvement in condition, are more accurately referred to as river rehabilitation. Rehabilitation can mean the process of returning to a previous condition or status along a restoration pathway, or creation of a new ecosystem that previously did not exist (Fryirs and Brierley, 2000; Figure 1.3). In landscapes subjected to profound human disturbance, such as urban, industrial, or intensively irrigated areas, management activities inevitably work towards creation goals. Both restoration and creation goals require rehabilitation strategies that strive to improve river condition, applying recovery notions to work towards the best attainable ecosystem values given the prevailing boundary conditions. The essential difference between restoration and creation goals lies in the perspective of regenerating the “old” or creating a “new” system (Higgs, 2003).

Various other terms have been used to characterize practices where the goals are not necessarily framed in ecosystem terms. For example, reclamation refers to returning a river to a useful or proper state, such that it is rescued from an undesirable condition (Higgs, 2003). In its original sense, reclamation referred to making land fit for cultivation, turning marginal land into productive acreage. Alternatively, remediation refers to the process of repairing ecological damage in a manner that does not focus on ecological integrity and is typically applied without reference to historical conditions (Higgs, 2003). Reclamation and remediation are quick-fix solutions to environmental problems that address concerns for human values, viewed separately from their ecosystem context.

The purpose and motivation behind any rehabilitation activity are integral to the goal sought. Specification of conservation, restoration, or creation goals provides an indication of the level and type of intervention that is required to improve riverine environments.

1.4 Determination of realistic goals in river rehabilitation practice

The process of river rehabilitation begins with a judgment that an ecosystem damaged by human activities will not regain its former characteristic properties in the near term, and that continued degradation may occur (Jackson et al., 1995). Approaches to repair river systems may focus on rehabilitating “products” (species or ecosystems) directly, or on “processes” which generate the desired products (Neimi et al., 1990; Richards et al., 2002). However, unless activities emphasize concerns for the rehabilitation of fundamental processes by which ecosystems work, notions of ecosystem integrity and related measures of biodiversity may be compromised (Cairns, 1988).

The goal of increasing heterogeneity across the spectrum of river diversity represents a flawed perception of ecological diversity and integrity. In some cases, the “natural” range of habitat structure may be very simple. Hence, heterogeneity or geomorphic complexity does not provide an appropriate measure of river health (see Fairweather, 1999). Simplistic goals framed in expressions such as “more is better” should be avoided (Richards et al., 2002). Use of integrity as a primary management goal avoids the pitfalls associated with assumptions that greater diversity or productivity is preferred.

Unlike many biotic characteristics, physical habitat is directly amenable to management through implementation of rehabilitation programs (Jacobson et al., 2001). Hence, many management initiatives focus on physical habitat creation and maintenance, recognizing that geomorphic river structure and function and vegetation associations must be appropriately reconstructed before sympathetic rehabilitation of riverine ecology will occur (Newbury and Gaboury, 1993; Barinaga, 1996). Getting the geomorphological structure of rivers right maximizes the ecological potential of a reach, in the hope that improvements in biological integrity will follow (i.e., the “field of dreams” hypothesis; Palmer et al., 1997). The simplest procedure with which to determine a suitable geomorphic structure and function is to replicate the natural character of “healthy” rivers of the same “type,” analyzed in equivalent landscape settings.

In any management endeavor, it is imperative to identify, justify, and communicate underlying goals, ensuring that the tasks and plan of action are visionary yet attainable. Although setting goals for rehabilitation is one of the most important steps in designing and implementing a project, it is often either overlooked entirely or not done very well (Hobbs, 2003). Success can only be measured if a definitive sense is provided of what it will look like. Unfortunately, however, there is a tendency to jump straight to the “doing” part of a project without clearly articulating the reasons why things are being done and what the outcome should be (Hobbs, 1994, 2003).

While sophisticated methodologies and techniques have arisen in the rapidly growing field of rehabilitation management, the conceptual foundations of much of this work remain vague (Ebersole et al., 1997). The pressure of timeframes, tangible results, and political objectives has lead to a preponderance of short-term, transitory rehabilitation projects that ignore the underlying capacities and developmental histories of the systems under consideration, and seldom place the study/treatment reach in its catchment context (Ebersole et al., 1997; Lake, 2001a, b). Unfortunately, many of these small-scale aquatic habitat enhancement projects have failed, or have proven to be ineffective (e.g., Frissell and Nawa, 1992).

Ensuring that goals are both explicit enough to be meaningful and realistic enough to be achievable is a key to the development of successful projects. Ideally, goals are decided inclusively, so that everyone with an interest in the outcomes of the project agrees with them (Hobbs, 2003). Scoping the future and generating a realistic vision of the desired river system are critical components of the planning process. The vision should be set over a 50 year timeframe (i.e., 1–2 generations; Jackson et al., 1995), such that ownership of outcomes can be achieved. A vision must be based on the best available information on the character, behavior, and evolution of the system, providing a basis to interpret the condition and trajectory of change from which desired future conditions can be established (Brierley and Fryirs, 2001). These concepts must be tied to analysis of biophysical linkages across a range of scales, enabling off-site impacts and lagged responses to disturbance events and/or rehabilitation treatments to be appraised (Boon, 1998).

To maximize effectiveness, rehabilitation efforts should incorporate spatiotemporal scales that are large enough to maintain the full range of habitats and biophysical linkages necessary for the biota to persist under the expected disturbance regime or prevailing boundary conditions. Although emphasis may be placed on a particular component or attribute, ultimate aims of longterm projects should focus on the whole system at the catchment scale (Bradshaw, 1996). Desired conditions for each reach should be specified as conservation, restoration, or creation goals, indicating how they fit within the overall catchment vision. Appropriate reference conditions should be specified for each reach.

Defining what is “natural” for a given type of river that operates under a certain set of prevailing boundary conditions provides an important step in identification of appropriate reference conditions against which to measure the geoecological integrity of a system and to identify target conditions for river rehabilitation. A “natural” river is defined here as “a dynamically adjusting system that behaves within a given range of variability that is appropriate for the river type and the boundary conditions under which it operates.” Within this definition, two points of clarification are worth noting. First, a “natural” condition displays the full range of expected or appropriate structures and processes for that type of river under prevailing catchment boundary conditions. This does not necessarily equate to a predisturbance state, as human impacts may have altered the nature, rate, and extent of river adjustments (Cairns, 1989). Second, a dynamically adjusted reach does not necessarily equate to an equilibrium state. Rather, the river adjusts to disturbance via flow, sediment, and vegetation interactions that fall within the natural range of variability that is deemed appropriate for the type of river under investigation.

Determination of appropriate reference conditions, whether a fixed historical point in time or a suite of geoecological conditions, represents a critical challenge in rehabilitation practice (Higgs, 2003). Systems in pristine condition serve as a point of reference rather than a prospective goal for river rehabilitation projects, although attributes of this ideal condition may be helpful in rehabilitation design. Identification of reference conditions aids interpretation of the rehabilitation potential of sites, thereby providing a basis to measure the success of rehabilitation activities.

Reference conditions can be determined on the basis of historical data (paleo-references), data derived from actual situations elsewhere, knowledge about system structure and functioning in general (theoretical insights), or a combination of these sources (Petts and Amoros, 1996; Jungwirth et al., 2002; Leuven and Poudevigne, 2002). The morphological configuration and functional attributes of a reference reach must be compatible with prevailing biophysical fluxes, such that they closely equate to a “natural” condition for the river type. Ideally, reference reaches are located in a similar position in the catchment and have near equivalent channel gradient, hydraulic, and hydrologic conditions (Kondolf and Downs, 1996). Unfortunately, it is often difficult to find appropriate reference conditions for many types of river, as “natural” or minimally impacted reaches no longer exist (Henry and Amoros, 1995; Ward et al., 2001). In the absence of good condition remnants, reference conditions can be constructed from historical inferences drawn from evolutionary sequences that indicate how a river has adjusted over an interval of time during which boundary conditions have remained relatively uniform. Selection of the most appropriate reference condition is situated within this sequence. Alternatively, a suite of desirability criteria derived for each type of river can be used to define a natural reference condition against which to compare other reaches (Fryirs, 2003). These criteria must encapsulate the forms and processes that are “expected” or “appropriate” for the river type. They draw on system-specific and process-based knowledge, along with findings from analysis of river history and assessment of available analogs. This approach provides a guiding image, or Leitbild, of the channel form that would naturally occur at the site, adjusted to account for irreversible changes to controlling factors (such as runoff regime) and for considerations based on cultural ecology (such as preservation of existing land uses or creation of habitat for endangered species; Kern, 1992; Jungwirth et al., 2002; Kondolf et al., 2003). Leitbilds can be used to provide a reference network of sites of high ecological status for each river type, as required by the European Union Water Framework Directive.

1.5 Managing river recovery processes in river rehabilitation practice

Exactly what is required in any rehabilitation initiative will depend on what is wrong. Options may range from limited intervention and a leave-alone policy, to mitigation or significant intervention, depending on how far desired outcomes are from the present condition. In some instances, sensitive, critical, or refuge habitats, and the stressors or constraints that limit desirable habitat, must be identified, and efforts made to relieve these stressors or constraints (Ebersole et al., 1997). Controlling factors that will not ameliorate naturally must be identified, and addressed first. Elsewhere, rehabilitation may involve the reduction, if not elimination, of biota such as successful invaders, in the hope of favoring native biota (Bradshaw, 1996). For a multitude of reasons, ranging from notions of naturalness that strive to preserve “wilderness,” to abject frustration at the inordinate cost and limited likelihood of success in adopted measures (sometimes referred to as basket cases, or “raising the Titanic”; Rutherfurd et al., 1999), it is sometimes advisable to pursue a passive approach to rehabilitation. This strategy, often referred to as the “do nothing option,” allows the river to self-adjust (cf., Hooke, 1999; Fryirs and Brierley, 2000; Parsons and Gilvear, 2002; Simon and Darby, 2002). Although these measures entail minimal intervention and cost, managers have negligible control over the characteristics and functioning of habitats (Jacobson et al., 2001).

In general terms, however, most contemporary approaches to river rehabilitation endeavor to “heal” river systems by enhancing natural recovery processes (Gore, 1985). Assessment of geomorphic river recovery is a predictive process that is based on the trajectory of change of a system in response to disturbance events. Recovery enhancement involves directing reach development along a desired trajectory to improve its geomorphic condition over a 50–100 year timeframe (Hobbs and Norton, 1996; Fryirs and Brierley 2000; Brierley et al., 2002). To achieve this goal, river rehabilitation activities must build on an understanding of the stage and direction of river degradation and/or recovery, determining whether the geomorphic condition of the river is improving, or continuing to deteriorate.

Assessment of geomorphic river condition measures whether the processes that shape river morphology are appropriate for the given setting, such that deviations from an expected set of attributes can be appraised (Figure 1.4; Kondolf and Larson, 1995; Maddock, 1999). Key consideration must be given to whether changes to the boundary conditions under which the river operates have brought about irreversible changes to river structure and function (Fryirs, 2003). Identification of good condition reaches provides a basis for their conservation. Elsewhere, critical forms and processes may be missing, accelerated, or anomalous, impacting on measures of geoecological functioning.

Understanding of geomorphic processes and their direction of change underpins rehabilitation strategies that embrace a philosophy of recovery enhancement (Gore, 1985; Heede and Rinne, 1990; Milner, 1994). Helping a river to help itself presents an appealing strategy for river rehabilitation activities because they cost nothing in themselves (although they may cost something to initiate), they are likely to be self-sustaining because they originate from within nature (although they may need nurturing in some situations), and they can be applied on a large scale (Bradshaw, 1996). Design and implementation of appropriate monitoring procedures are integral in gauging the success of these strategies.

Figure 1.4 Habitat diversity for good, moderate, and poor condition variants of the same river typeNatural or expected character and behavior varies for differing types of river. Some may be relatively complex, others are relatively simple. Natural species adaptations have adapted to these conditions. Assessments of geomorphic river condition must take this into account, determining whether rehabilitation activities should increase (a) or decrease (b) the geomorphic heterogeneity of the type of river under investigation. Increasing geomorphic heterogeneity is not an appropriate goal for all types of river, and may have undesirable ecological outcomes. More appropriate strategies work with natural diversity and river change.

The process of river rehabilitation is a learning experience that requires ongoing and effective monitoring in order to evaluate and respond to findings. Measuring success must include the possibility of measuring failure, enabling midcourse corrections, or even complete changes in direction (Hobbs, 2003). If effectively documented, each project can be considered as an experiment, so that failure can be just as valuable to science as success, provided lessons are learnt. Goals or performance targets must be related to ecological outcomes and be measurable in terms such as increases in health indicators (e.g., increasing similarity of species or structure with the reference community), or decreases in indicators of degradation (e.g., active erosion, salinity extent or impact, nonnative plant cover). The choice of parameters to be monitored must go hand in hand with the setting of goals, ensuring that they are relevant to the type of river under consideration, so that changes in condition can be meaningfully captured. Baseline data are required to evaluate changes induced by the project, including a detailed historical study (Downs and Kondolf, 2002). Monitoring should be applied over an extensive period, at least a decade, with surveys conducted after each flood above a predetermined threshold (Kondolf and Micheli, 1995). These various components are integral parts of effective river rehabilitation practice.

1.6 Overview of the River Styles framework

Best practice in natural resources management requires appropriate understanding of the resource that is being managed, and effective use of the best available information. In river management terms, catchment-scale information on the character, behavior, distribution, and condition of different river types is required if management strategies are to “work with nature.” Given that rivers demonstrate remarkably different character, behavior, and evolutionary traits, both between- and within-catchments, individual catchments need to be managed in a flexible manner, recognizing what forms and processes occur where, why, how often, and how these processes have changed over time. The key challenge is to understand why rivers are the way they are, how they have changed, and how they are likely to look and behave in the future. Such insights are fundamental to our efforts at rehabilitation, guiding what can be achieved and the best way to get there.

This book presents a coherent set of procedural guidelines, termed the River Styles framework, with which to document the geomorphic structure and function of rivers, and appraise patterns of river types and their biophysical linkages in a catchment context. Meaningful and effective description of river character and behavior are tied to explanation of controls on why rivers are the way they are, how they have evolved, and the causes of change. These insights are used to predict likely river futures, framed in terms of the contemporary condition, evolution, and recovery potential of any given reach, and understanding of its trajectory of change (Figure 1.5).

The River Styles framework is a rigorous yet flexible scheme with which to structure observations and interpretations of geomorphic forms and processes. A structured basis of enquiry is applied to develop a catchment-wide package of physical information with which to frame management activities (Figure 1.6). This package guides insights into the type of river character and behavior that is expected for any given field setting and the type of adjustments that may be experienced by that type of river. A catchment-framed nested hierarchical arrangement is used to analyze landscapes in terms of their constituent parts. Reach-scale forms and processes are viewed in context of catchment-scale patterns and rates of biophysical fluxes. Separate layers of information are derived to appraise river character and behavior, geomorphic condition, and recovery. Definition of ongoing adjustments around a characteristic state(s) enables differentiation of the behavioral regime of a given river type from river change. Analysis of system evolution is undertaken to appraise geomorphic river condition in context of “expected attributes” of river character and behavior given the reach setting. Interpretation of catchment-specific linkages of biophysical processes provides a basis with which to assess likely future patterns of adjustment and the geomorphic recovery potential of each reach. The capacity, type, and rate of recovery response of any given type of river are dependent on the nature and extent of disturbance, the inherent sensitivity of the river type, and the operation of biophysical fluxes (both now and into the future) at any given point in the landscape. When these notions are combined with interpretations of limiting factors to recovery and appraisal of ongoing and likely future pressures that will shape river forms and processes, a basis is provided to assess likely future river condition, identify sensitive reaches and associated off-site impacts, and determine the degree/rate of propagating impacts throughout a catchment.

Figure 1.5 Routes to description, explanation, and prediction

The strategy outlined in this book emphasizes the need to understand individual systems, their idiosyncrasies of forms and processes, and evolutionary traits and biophysical linkages, as a basis to determine options for management – in planning, policy, and design terms. System configuration and history ensure that each catchment is unique. In making inferences from system-specific information, cross-reference is made to theoretical and empirical relationships to explain system behavior and predict likely future conditions. Principles outlined in this book provide a conceptual tool with which to read and interpret landscapes, rather than a quantitative approach to analysis of river forms and processes. Application of these procedures provides the groundwork for more detailed site- or reach-specific investigations.

Figure 1.6 Stages of the River Styles framework

However, application of geomorphic principles in the determination of sustainable river management practices is far from a simple task. The need for system-specific knowledge and appropriate skills with which to interpret river evolution and the changing nature of biophysical linkages (and their consequences) ensure that such exercises cannot be meaningfully undertaken using a prescriptive cook-book approach. The cautious, data intensive measures applied in this book are considered to present a far better perspective than managing rivers to some norm! Hopefully, lessons have been learnt from the homogenization of river courses under former management regimes.

Management applications of the River Styles framework focus on the derivation of a catchment-scale vision for conservation and rehabilitation, identification of reach-specific target conditions that fit into the bigger-picture vision, and application of a geomorphologically based prioritization procedure which outlines the sequencing of actions that best underpins the likelihood of management success. The framework does not provide direct guidance into river rehabilitation design and selection of the most appropriate technique. Rather, emphasis is placed on the need to appraise each field situation separately, viewed within its catchment context and evolutionary history. The underlying catchcry in applications of the River Styles framework is “KNOW YOUR CATCHMENT.”

1.7 Layout and structure of the book

This book comprises four parts (Figure 1.7). Part A outlines the geoecological basis for river management. Chapter 2 documents the use of geomorphology as a physical template for integrating biophysical processes, working with linkages of biophysical processes within a catchment framework, and the need to respect diversity (work with nature). Chapter 3 outlines how geomorphic principles provide a basis for river management programs to work with change through understanding of controls on river character and behavior and prediction of likely future adjustments.

Geomorphic principles that underpin applications of the River Styles framework are documented in Part B. Pertinent literature is reviewed to assess river character (Chapter 4), interpret river behavior (Chapter 5), analyze river evolution and change (Chapter 6), and appraise river responses to human disturbance (Chapter 7).

The River Styles framework is presented in Part C. An overview of the framework in Chapter 8 is followed by a brief summary of practical and logistical issues that should be resolved prior to its application. Chapter 9 presents the step-by-step procedure used to classify and interpret river character and behavior in Stage One of the framework.

Figure 1.7 Structure of the book

Procedures used to assess geomorphic condition of rivers in Stage Two of the framework are presented in Chapter 10. Evolutionary insights are used to interpret the future trajectory and recovery potential of rivers in Stage Three of the framework (Chapter 11). Finally, Chapter 12 outlines Stage Four of the River Styles framework, which can be used to develop catchment-framed visions for management, identify target conditions for river rehabilitation, and prioritize where conservation and rehabilitation should take place.

The concluding chapter, in Part D, outlines an optimistic (aspirational) perspective on future river management practices and outcomes (Chapter 13).

PART A

The geoecological basis of river management

(A)n understanding of the nature of the building blocks that compose a particular landscape is fundamental to understanding how geomorphological processes function as ecological disturbance processes at the watershed or landscape scale.

Dave Montgomery, 2001, p. 249

Overview of Part A

This part demonstrates how principles from fluvial geomorphology can be used to develop an ecosystem approach to river analysis and management. In Chapter 2, spatial considerations in geomorphology and management practice are framed in terms of a nested hierarchical approach to catchment characterization. Principles from fluvial geomorphology are shown to provide an integrative physical template with which to assess habitat associations and linkages of biophysical processes in landscapes. Finally, the concept of respecting diversity is introduced, indicating why management strategies should strive to maintain unique or distinctive attributes of river courses.

Chapter 3 outlines how theoretical and field-based insights must be combined to meaningfully describe and explain river systems. These insights provide a critical platform for our efforts at prediction. Themes discussed in this chapter include the need for management programs to work with change, moving beyond notions of equilibrium and stability used in engineering applications. Timeframes of river adjustment, assessment of controls on river character and behavior, and approaches to prediction are also outlined.

CHAPTER 2

Spatial considerations in aquatic ecosystem management

The average textbook of fluvial geomorphology devotes equal space to channel-scale structure, process, and dynamics and to basin-scale structure, process, and dynamics. Stream ecology has focussed almost exclusively on the former. Abundant tools exist for a fruitful, creative incursion into the realm of the latter.

Stuart Fisher, 1997, p. 313

2.1 Introduction and chapter structure

The diversity and complexity of biophysical interactions that fashion the structure and function of aquatic ecosystems present an intriguing and demanding challenge for river managers. In this chapter, spatial considerations in the management of aquatic ecosystems are addressed. Emphasis is placed on geomorphic principles that underpin ecological considerations in river rehabilitation practice.

Application of a nested hierarchical framework aids the differentiation of scalar components of river systems (Section 2.2). Research and management applications of geoecological insights are framed in terms of their landscape context in Section 2.3, where habitat, flow, sediment transfer, and vegetation management considerations are examined atop a geomorphic template. Longitudinal, lateral, and vertical dimensions of biophysical fluxes are outlined in relation to these considerations in Section 2.4. Finally, the catchment-specific nature of these relationships prompts the need to respect diversity in the management of aquatic ecosystems (Section 2.5).

2.2 Spatial scales of analysis in aquatic geoecology: A nested hierarchical approach

The scale at which observations of the natural world are made constrains what is seen. A head bowed over a gravel bar measuring the sizes of pebbles provides a very different perspective to that derived by viewing the landscape from the highest local point, or an aerial overview. Physical scale imposes various limitations on system structure and function. For example, bed material texture in flume studies does not scale in a linear manner to channel size, presenting considerable problems with dimensionality in extrapolating laboratory findings to field situations. In general, landscape complexity increases as size increases (Schumm, 1991). For example, while a small subcatchment may lie within one climatic region, form on one lithologic unit, and be subjected to one type of land use, a larger catchment may span climatic, lithologic, and land-use boundaries, and is thus more complex. Scalar considerations can also be appraised in relational terms. For example, a point bar scales in size relative to its channel, whether measured for a third-order stream with a catchment area of 50 km2, or the trunk stream of the Amazon.

Relationships between scales, and their significance in determining measures of system functioning, vary for differing branches of enquiry. For example, predation and species–species interactions operate at differing physical scales to geomorphic interactions that shape river morphology. The challenge for riverine ecologists is to match the scales of their observations and experiments to the characteristic scales of the phenomena that they investigate (Cooper et al., 1998). A coherent analytical framework is required to meaningfully interlink these scales.

Recognition of the controls imposed on small-scale (and short-term) physical features and processes in rivers by larger-scale (and longer-term) factors has led to the development of nested hierarchical models of physical organization (Table 2.1, Figure 2.1; Frissell et al., 1986; Naiman et al., 1992; Poole, 2002). Characteristics that vary over small spatial and temporal scales are constrained by, or nested within, boundaries set by characteristics that vary over large scales. In general terms, the larger the scale of analysis, the greater the level of generality of forms and processes involved. Large-scale attributes are delineated using large-scale characteristics such as relief and valley slope, and necessarily include a great deal of variation in small-scale characteristics such as flow type and substrate. Different scalar units in the nested hierarchy are commonly not discrete physical entities. Rather, they are part of an inordinately complex continuum in which the dimensions of units at each scale overlap significantly. Interaction between units, at each scale and between scales, determines system character and behavior (Ward, 1989; Naiman et al., 1992; Parsons et al., 2003, 2004).