River Styles Research Articles

Geomorphic context in process‐based river restoration

AbstractProcess‐based river restoration seeks to restore processes such as channel‐floodplain connectivity that create and maintain river corridor functions. Process‐based restoration can fail to produce the desired results if geomorphic context is not effectively incorporated into restoration design. Geomorphic context of a river reach refers to the controls on contemporary river form and process. Controls at the catchment‐ to reach‐scale include geologic history, biophysical characteristics, legacies of past human alterations, position within the river network, river corridor geometry, base level stability, disturbance regime, and contemporary human alterations of the river corridor. We conceptualize a river corridor as reflecting the interactions among fluxes of material and the geomorphic context. We discuss how an understanding of geomorphic context can be used to select a restoration approach and provide examples of how restoration can fail to achieve desired outcomes when geomorphic context is not considered. Within the toolbox of methods used to implement process‐based restoration, we differentiate the alteration of inputs to the river corridor and fluxes of material through the corridor from alteration of form and/or connectivity within the river corridor. Historical, biotic, geologic/geomorphic, and reference sites can be used to inform process‐based restoration targets. Restoration is strongly influenced by human perceptions of what is appropriate and achievable at a site and diverse communities influencing restoration at a site may differ in their perceptions. Geomorphically based conceptual guidelines, such as the River Styles Framework, provide an effective platform for incorporating an understanding of geomorphic context into process‐based river restoration.

Geomorphic changes in river styles in a typical catchment of the Brazilian semiarid region

Rivers in drylands behave differently from those in wetlands due to their irregular flow patterns. This study investigated morphological changes in the Brazilian semiarid region to infer the evolutionary trend of the river. Consequently, the focus was on analyzing the fluvial dynamics and the propensity for change in rivers within the Piranhas River basin. River styles were defined based on the typologies of valley configuration, planimetric shape, sets of geomorphic units, and bed material attributes of the rivers under analysis. In total, eight river styles were identified, broadly classified into confined (two styles), partially confined (three styles), and laterally unconfined (three styles). Confined styles are typically associated with areas near the headwaters, characterized by rocky banks and beds with high flow energy. These channels were found to have low sensitivity to changes in geomorphic conditions. In contrast, unconfined styles predominantly displayed high sensitivity in their stretches, primarily due to the presence of a rocky bed. In the case of partially-confined styles, channels with moderate sensitivity were primarily observed. These channels exhibit a strong tendency to adapt based on their geoindicators and geomorphic conditions, rather than external influences. Interestingly, the resistance to change in geomorphic conditions was linked to unexpected river characteristics within the catchment. Lastly, a historical analysis of the flow allowed an understanding of the dynamics of the styles that displayed a higher propensity to change. This unveiled possible high-magnitude events that may have caused morphological alterations in these styles.

A GIS workflow for the identification of corridors of geomorphic river recovery across landscapes.

The provision of a simplified GIS workflow to analyse the Open Access NSW River Styles database provides non-technical GIS users in river management with the ability to quickly and efficiently obtain information to assist them in catchment-scale rehabilitation prioritisation. Publicly available proprietary GIS software, standard GIS tools, and a packaged digital elevation model are used to demonstrate the ease of analysis for those with some GIS skills, to establish where corridors of geomorphic river recovery occur or could be built at-scale. Rather than a 'single use' report, this novel application of GIS methods is designed to be used by those responsible for river management, replicated across landscapes and adjusted according to preferences. Decision making becomes more cost effective, and adaptive to local circumstances and changing river management priorities. The method could also be adjusted and applied to other river monitoring and condition datasets where polyline data layers are available.

Identifying corridors of river recovery in coastal NSW Australia, for use in river management decision support and prioritisation systems.

By connecting corridors of river recovery, resilience can be built into river systems to mitigate against future floods and droughts driven by anthropogenic disturbance or climate extremes. However, identifying where these corridors can be built is still lacking in river management practice. The Open Access NSW River Styles database contains comprehensive information on geomorphic river condition and recovery potential. The database can be used to systematically analyse where corridors of river recovery could be created via conservation or rehabilitation. Analysis was undertaken in ArcGIS using the recovery potential layer along 84,342 km of freshwater stream length, across 20 catchments of coastal NSW. We identified 4,905 km of reach connections, defined as an upstream to downstream section of river that is connected end-to-end, and 17,429 km of loci connections defined as more isolated sections of river from which recovery can be seeded and extended into adjacent reaches. There was significant spatial variability in the types and lengths of connections made across the catchments. Some catchments have significant potential to build corridors of recovery along large sections of river, whereas other catchments are more fragmented. These results provide practitioners with a user-friendly distillation of where river conservation and rehabilitation activities could be focussed when working with river recovery in practice. Combined with local on-ground knowledge, this information forms an important input to evidence-based prioritisation and decision making in river management.

River adjustments, geomorphic sensitivity and management implications in the Waipā catchment, Aotearoa New Zealand

Assessment of River Styles, accompanied by time series analysis of historic imagery and geomorphic change detection techniques are used to explain the capacity for river adjustment (geomorphic sensitivity) in relation to the distribution of stream power along 3000 km of channels (3rd Strahler order and greater) to better inform management initiatives in the Waipā catchment, the largest tributary of the Waikato River on the North Island of Aotearoa, New Zealand. Unlike most dynamically adjusting physical landscapes of Aotearoa, most reaches within the Waipā catchment are resistant to geomorphic change. Only 3% of the studied river length has experienced significant planform adjustment since the 1950s and is considered highly sensitive to adjustment. Contemporary alluvial dynamism is largely restricted to gravel bed reaches in high energy rivers within the piedmont zone. The capacity for lateral adjustment in headwater stream courses is restricted by the imprint of past volcanic activity. Further downstream capacity is also limited because of terrace constraints as a result of post-glacial base-level fall, and the entrenchment of the Waikato Fan. Anthropogenic modifications in the catchment include drained wetlands, straightened channels, reinforced banks and emplaced artificial levees (stopbanks) in the few reaches that were prone to adjustment. Highlighting geomorphologically-sensitive reaches at the catchment-scale helps to better prioritise rehabilitation efforts and to support the design and implementation of proactive management plans.

Geomorphic characterization of a seasonal river network in semi-arid western India using the River Styles Framework

The imprint of geologic, climatic and anthropogenic memory as controls on geomorphic river diversity is assessed for twelve River Styles in the Sabarmati Catchment. Geologic controls are the primary determinant of river character and behavior in the hinterland and pediment landscape units, where headwater streams transition to partly confined valleys and gorges with distinct structural lineations in a rectangular drainage network. Climate memory imprints entrenched rivers that make up alluvial fan and alluvial plain landscape units of the mid-lower catchment, shaped by phases of sediment aggradation and subsequent incision in response to enhanced monsoonal rains around 10 ka. Terraces constrain channels within confined and partly confined valleys with occasional and discontinuous floodplains respectively. Laterally unconfined channels are only found in the lower parts of the catchment, immediately upstream of the estuary/delta. Limited space for adjustment, impacts of flow regulation and ephemeral conditions restrict the range of contemporary river morphodynamics, but ridges and swales and abandoned channels on floodplains indicate more dynamic conditions in the past. Impacts of anthropogenic memory are most pronounced in the stopbank-controlled, barrage- and dam-impacted reaches, especially in the cities of Gandhinagar and Ahmedabad. An explanation of controls upon geomorphic river diversity, including an assessment of the role of stream power, presents a coherent platform to develop geomorphologically-informed approaches to river management.

Assessment of the geo‐eco‐hydrological condition of anabranching reaches in the Source Zone of the Yellow River, western China

AbstractA geo‐eco‐hydrological approach is developed and applied to assess river condition for three anabranching reaches in the Source Zone of the Yellow River. Building on principles of the River Styles Framework, attributes used to assess river condition are tailored to measure key attributes of the character and behavior for the type of river under consideration. Hydrogeomorphic process linkages with riparian vegetation function are appraised using the Fluvial Biogeomorphic Succession Model for each reach. Reference conditions incorporate measures of river geo‐eco‐hydrological structural integrity and functional connectivity, relating the expected “best achievable” conditions to prevailing land use practices in these grazing adapted grassland ecosystems. Contemporary conditions closely approximate expected reference conditions in hydro‐geomorphic terms. While vegetation interactions function effectively in the active channel zone, they are subject to land use pressures in many floodplain areas. Minimizing impacts of direct anthropogenic disturbance, while promoting passive management practices that support self‐sustaining processes, are considered to offer the best prospect to maintain good river condition in these reaches. Major commitment to environmental protection in this area makes this a realistic possibility. The generic approach to analysis of geo‐eco‐hydrological condition is readily transferable to other situations.

Things we can do now that we could not do before: Developing and using a cross-scalar, state-wide database to support geomorphologically-informed river management.

A fundamental premise of river management is that practitioners understand the resource they are working with. In river management this requires that baseline information is available on the structure, function, health and trajectory of rivers. Such information provides the basis to contextualise, to plan, to be proactive, to prioritise, to set visions, to set goals and to undertake objective, pragmatic, transparent and evidence-based decision making. In this paper we present the State-wide NSW River Styles database, the largest and most comprehensive dataset of geomorphic river type, condition and recovery potential available in Australia. The database is an Open Access product covering over 216,600 km of stream length in an area of 802,000 km2. The availability of the database presents unprecedented opportunities to systematically consider river management issues at local, catchment, regional and state-wide scales, and appropriately contextualise applications in relation to programs at other scales (e.g. internationally)-something that cannot be achieved independent from, or without, such a database. We present summary findings from the database and demonstrate through use of examples how the database has been used in geomorphologically-informed river management. We also provide a cautionary note on the limitations of the database and expert advice on lessons learnt during its development to aid others who are undertaking similar analyses.

Landscape evolution of the Salamanca watershed, Araripe Plateau: Insights from a river channel morphological classification

The drainage network of the Brazilian semi-arid responds directly to the complexity of the geomorphic background and surface processes. In this regional context, the Araripe Plateau, a table-like landform that reaches up of 950 m in elevation, stands out as a peculiar physiographic setting. The present work proposes an analysis of the Plateau's fluvial system based on channel morphology descriptive criteria, in relation to their morphostratigraphic scenarios. The research sought to explore river typologies, dominant surface processes and geomorphic changes in the drainage system throughout the Holocene. Seven fluvial styles have been identified in the Salamanca River watershed, expressing lithological controls of the underlying sedimentary rocks, morphotectonic influence, variability in rainfall input, as well as changes in land use. Headwaters' channels cut through the sandstone of the structural summit surface and the unconsolidated sedimentary infills of topographic hollows along the escarpment base. On the hillslopes, downstream of the escarpment, the incised meandering river style with occasional pocket plains attest to shifts in patterns of fluvial dissection due to changes in base level. In the peripheral depression (Vale do Cariri), at an average elevation of 400 m, the arroyo and floodout river styles prevail, displaying a sequence of incised and non-incised river stretches, reflecting the operation of recent cut-and-fill processes mostly controlled by the interannual rainfall variability. Cut-and-fill processes operating within the channels have prevailed all through the Holocene, as suggested by morphostratigraphical evidence, alternating overall valley bottom filling episodes with river entrenching periods (paleo-connectivity). Base level change during the upper Holocene did not result in comprehensive sediment delivery to the channel networks, as attested by remaining discontinuous pocket plains and fluvial terraces.

A Computer Aided Approach for River Styles—Inspired Characterization of Large Basins: A Structured Procedure and Support Tools

This paper presents a systematic procedure for developing a characterization and classification of river reaches inspired by the River Styles Framework, through which insight can be gained about the understanding of river behavior. Our procedure takes advantage of several computer based “tools”, i.e., algorithms implemented in software packages of various types, from “simple” Excel sheets to sophisticated algorithms in Python language, in general all supported by Geographic Information Systems (GIS). The main potentially useful, existing tools for this specific aim are discussed here, revealing their strengths and weaknesses. New, complementary or alternative tools that have been developed in the project feeding this paper are presented, which can contribute to the scientific community and stakeholders of the topic. The main result of our research is a structured and practical guide (a ToolBox Manual) that can support practitioners and researchers wishing to characterize and classify large rivers, based on the River Styles Framework. The main contribution is that this set of ideas, solutions, and tools, makes this type of exercise significantly more transparent and at the same time much less subjective. Moreover, the procedure is applicable to large systems and does not require more information than that generally available also in developing or emerging countries.

Identifying threshold responses of Australian dryland rivers to future hydroclimatic change

Rivers provide crucial ecosystem services in water-stressed drylands. Australian dryland rivers are geomorphologically diverse, ranging from through-going, single channels to discontinuous, multi-channelled systems, yet we have limited understanding of their sensitivity to future hydroclimatic changes. Here, we characterise for the first time the geomorphology of 29 dryland rivers with catchments across a humid to arid gradient covering >1,800,000 km2 of continental eastern and central Australia. Statistical separation of five specific dominantly alluvial river types and quantification of their present-day catchment hydroclimates enables identification of potential thresholds of change. Projected aridity increases across eastern Australia by 2070 (RCP4.5) will result in ~80% of the dryland rivers crossing a threshold from one type to another, manifesting in major geomorphological changes. Dramatic cases will see currently through-going rivers (e.g. Murrumbidgee, Macintyre) experience step changes towards greater discontinuity, characterised by pronounced downstream declines in channel size and local termination. Expanding our approach to include other river styles (e.g. mixed bedrock-alluvial) would allow similar analyses of dryland rivers globally where hydroclimate is an important driver of change. Early identification of dryland river responses to future hydroclimatic change has far-reaching implications for the ~2 billion people that live in drylands and rely on riverine ecosystem services.

A Computer Aided Approach for River Styles—Inspired Characterization of Large Basins: The Magdalena River (Colombia)

This paper addresses the geomorphic characterization and classification of large rivers in a framework of scarce information. This is inspired by the River Styles Framework with some modifications that make the process more straightforward and accessible to practitioners and more applicable to large basins, while reducing the subjective, expert-based inputs, as the process is now more systematic. To this aim, it utilizes innovative criteria and some computer-aided procedures and tools based on GIS, Excel and Python. This approach sheds light on the character and the behavior of rivers, which is key to informing planning, management and restoration. The application to the Magdalena River (Colombia) illustrates the characterization and classification process and the type of results, which ultimately highlight the great geomorphic diversity of that river. The process is applicable to many other rivers worldwide.

Let the river erode! Enabling lateral migration increases geomorphic unit diversity.

River restoration practice frequently employs conservative designs that create and maintain prescribed, static morphology. Such approaches ignore an emerging understanding of resilient river systems that typically adjust their morphology in response to hydrologic, vegetative and sediment supply changes. As such, using increased dynamism as a restoration design objective will arguably yield more diverse and productive habitats, better managed expectations, and more self-sustaining outcomes. Here, we answer the following question: does restoring lateral migration in a channelised river that was once a wandering gravel-bed river, result in more diverse in-channel geomorphology? We acquired pre- and post-restoration topographic surveys on a segment of the Allt Lorgy, Scotland to quantify morphodynamics and systematically map geomorphic units, using Geomorphic Unit Tool (GUT) software. GUT implements topographic definitions to discriminate between a taxonomy of fluvial landforms that have been developed from an extension of the River Styles framework, using 3-tiered hierarchy: (1) differentiation based on stage or elevation relative to channel; (2) classification of form based on shape (mound, bowl, trough, saddle, plane, wall); and (3) mapping geomorphic units based on attributes (e.g., position and orientation). Results showed restoration increased geomorphic unit diversity, with the Shannon Diversity Index increasing from 1.40 pre-restoration (2012) to 2.04 (2014) and 2.05 (2016) after restoration. Channel widening, due to bank erosion, caused aerial coverage of in-channel geomorphic units to increase 23% after restoration and 6% further in the two-years following restoration. Once bank protection was removed, allowing bank erosion yieled a local supply of sediment to enable the formation and maintenance of lateral and point bars, riffles and diagonal bar complexes, and instream wood created structurally-forced pools and riffles. The methodology used systematically quantifies how geomorphic unit diversity increases when a river is given back its freedom space. The framework allows for testing restoration design hypotheses in post-project appraisal.

LEARNING, DOING AND PROFESSIONAL DEVELOPMENT – THE RIVER STYLES FRAMEWORK AS A TOOL TO SUPPORT THE DEVELOPMENT OF COHERENT AND STRATEGIC APPROACHES FOR LAND AND WATER MANAGEMENT IN BRAZIL

Ongoing development, training and adaptive learning are fundamental to professional practice in river science and management. River Styles Framework provides a coherent, carefully structured (scaffolded) approach that synthesises geomorphic understandings of rivers as a baseline to support river management applications. As the approach is generic, principles and procedures can applied in any setting. The Framework and its applications build on fundamental research into river forms and processes. Importantly, the Framework was developed in collaboration with river management agencies in New South Wales, Australia and has been used in collaboration with practitioners elsewhere in the world. This paper documents the process used to teach the five-day River Styles professional short course in Brazil, September 2017. We report upon some pedagogical foundations of the Framework to explain the approach to teaching. We present an overview of the types of exercises taught in Brazil, showing how local fieldwork and case studies support the uptake of this geomorphic information to inform river management. We emphasise the importance of careful planning in delivering a coherent product that integrates remotely-sensed work, field interpretation skills and lecture/practical class exercises. These exercises build upon foundation research in fluvial geomorphology in the Macaé Catchment in Rio de Janeiro State.

THE USE OF THE RIVER STYLES FRAMEWORK AS A TOOL TO ‘WORK WITH NATURE’ IN MANAGING RIVERS IN BRAZIL: EXAMPLES FROM THE MACAÉ CATCHMENT

Integrative approaches to land and water management apply scientifically informed policies that build upon a landscape template. The River Styles Framework supports the development and application of proactive, strategic and cost-effective management plans. This paper outlines eight key principles that build upon the River Styles Framework: (1) use a landscape template as an integrative platform; (2) respect the inherent diversity of river forms and processes; (3) work with variability, adjustment and change; (4) know your catchment, understanding patterns of river types and tributary-trunk stream relationships; (5) compare like with like in assessing geomorphic river condition; (6) forecast prospective river futures to set moving targets for management; (7) apply a conservation-first and recovery enhancement ethos in the development of visionary yet realistically achievable management plans that have a clear evidence base for prioritization of actions; and (8) monitor and learn effectively using adaptive management principles. The application of each of these principles is demonstrated using a case study from the Macaé Catchment in Rio de Janeiro State.

To plug‐in or not to plug‐in? Geomorphic analysis of rivers using the River Styles Framework in an era of big data acquisition and automation

AbstractIn an era of big‐data acquisition and semiautomation of geomorphic river surveys, it is timely to consider how to better integrate this into existing and widely used conceptual frameworks and approaches to analysis. We demonstrate how Stage 1 of the River Styles Framework, which entails identification and interpretation of river character and behavior, patterns and controls, can be used as a “powerboard” into which available, developing and future semiautomated tools and workflows can be plugged (or unplugged). Prospectively, such approaches will increase the efficiency and scope of analyses, providing unprecedented insights into the diversity of rivers and their morphodynamics. We appraise the role of human decision‐making in conducting expert‐manual analyses and interpretations. Genuine integration of big‐data analytics, remote‐sensing based tools for semiautomated river analysis with expert‐manual interpretations including field insights, will be an essential ingredient to fully exploit emerging computational and remote sensing technologies to advance our understanding of river systems, to translate information into knowledge, and raise the standards of practice in river science and management.This article is categorized under:Water and Life > Conservation, Management, and AwarenessWater and Life >MethodsEngineering Water > Planning WaterEngineering Water > Sustainable Engineering of Water

What’s in a name? A naming convention for geomorphic river types using the River Styles Framework

Meaningful iteration between place-based knowledge of rivers and generalised, theoretically-framed understandings is a significant challenge in river science and management. How can we communicate knowledge of the inherent complexity of river systems in light of managerial quests for simple, easy-to-apply frameworks that can be used by a wide range of practitioners, such that we can meaningfully transfer experiences in river science and management from one situation to another? Identification, definition, classification and naming are vital parts of this process. In a sense, a name is like a ‘brand’, for which a consistency of product is expected. The River Styles Framework is a flexible, open-ended approach to river science and management. The Framework applies a set of hierarchical principles to differentiate reaches, interpret their process-based behaviour and examine interactions between patterns of reaches at the catchment scale. Here we outline an evolution and tightening of the Framework to better communicate how to identify and name types of river at the reach scale. Like the River Styles Framework itself, the naming convention applies hierarchical procedures, starting at the valley setting scale, and incorporating analyses of river planform, channel and floodplain landforms (geomorphic units) and bed material texture. Using a series of examples from around the world, we show how this naming convention can be applied to name river reaches and can be adapted to particular purposes in a consistent, readily communicable manner. We outline various challenges that are faced in managing the use of such a naming convention.

Geomorphic context in rivers

Geomorphic context refers to the geomorphic setting of a river reach, which is defined as a length of river with consistent valley and channel geometry. Context includes spatial dimensions of geometry, location within a drainage basin, and location within a global context. Context also includes temporal dimensions of the frequency and duration of specific processes influencing the river reach and the historical sequence of natural and human-induced processes that continue to influence process and form in the river reach. These spatial and temporal characteristics interact to create a geomorphic context that governs the contemporary form of the river corridor, the rates and processes by which diverse materials move through the corridor, and the adjustments of form and process in response to disturbances. Context matters for both basic understanding and effective management of river corridors. Examples of widely used formal articulations of geomorphic context include a bedform-based classification of mountain streams, geomorphic process domains, and river styles. Each has been applied to understanding and predicting longitudinal variations in stream power, sediment budgets, habitat and biotic communities, resilience to disturbance, and other characteristics of rivers. The three Cs of rivers—complexity (or spatial heterogeneity), connectivity, and context—provide a conceptual framework for river research and management.

Examining the utility of river restoration approaches for flood mitigation and channel stability enhancement: a recent review

Increased anthropogenic activities, especially within the river corridor, have progressively disrupted natural flow regimes and segmented channel–floodplain connectivity. Consequent alterations in flow dynamics have caused geomorphic and hydrological changes in channel morphology and behaviour, decreasing their natural replenishment capacity, thereby causing their degradation. The simultaneous disconnection of the channel from its natural floodplain due to intensive cultivation and surface paving has also reduced possible floodwater outlets or seepage zones, which would have otherwise functioned as storm run-off storage buffers that reduced the flood peak downstream. Such occurrences of flow disruption, especially in low-relief topographic regions buffeted by high intensity monsoonal storms, accentuate flood-like situations, since natural channel capacities to transport excess storm-water are diminished, with this further enhancing ongoing or inducing riverbank erosion. Such events have accounted for much loss of life, livelihood and property worldwide and to mitigate their intensity, river restoration techniques have been promoted. These place greater emphasis on ecological management measures that attempt to restore and rehabilitate the geomorphic and hydrological functionality of the stream to a prior, more pristine state to achieve channel stability and regulate flows. Thus, frameworks based on river corridor management, riparian buffer creation and the River Styles Framework instituted guidelines, aided by geospatial analysis techniques, have yielded significant management strategies for such flood- and erosion-affected degraded channel corridors. This paper presents a recent review of such ecological techniques of flood and channel management, especially in monsoonal environments, while highlighting the issues concerning their implementation in developing nations.

A geomorphological characterisation of river systems in South Africa: A case study of the Sabie River

Fluvial geomorphology affects river character, behaviour, evolution, trajectory of change and recovery potential, and as such affects biophysical interactions within a catchment. Water bodies in South Africa, in common with many other water-stressed parts of the world, are generally under threat due to increasing natural and anthropogenic influences including aridity, siltation and pollution, as well as climate and environmental change. This study reports on a case study to characterise the geomorphology of different river systems in South Africa, with the aim of better understanding their properties, controls, and implications for biophysical interactions including water quality, biodiversity (aquatic and riparian), and human activity within the catchment. The approach adopted is based on the River Styles® framework (RSF), a geomorphology-based approach developed for rivers in New Zealand and Australia, but applied here for the first time to South Africa. Based on analysis of remote sensing imagery, SRTM-2 digital topographic data and field observations on sites through the entire river system, six geomorphic elements were identified along the Sabie River, northeast South Africa (gorge, bedrock-forced meander, low-moderate sinuosity planform controlled sand bed, meandering sand bed, low sinuosity fine grained sand bed, and floodouts), using the RSF classification scheme and based on the RSF procedural tree of Brierley and Fryirs (2005). Previous geomorphological studies along the Sabie River have shown that different reaches respond differently to episodic floods; we use these data to link river geomorphological character (as defined by the RSF) to the hydrodynamic conditions and processes giving rise to such character. This RSF approach can be used to develop a new management approach for river systems that considers their functional biophysical behaviour within individual reaches, rather than considering them as homogeneous and uniform systems.