Arrested geomorphic trajectories and the long-term hidden potential for change

The Barekese Reservoir is a facility for reserving water for treatment and subsequent consumption by the populace of the Kumasi conurbation and its environs. The reservoir provides over 80% of the total public water supply to the Kumasi locale and is plagued by persistent degradation through human activities throughout the catchment. This situation raises concern on the regional deterioration of water quality and quantity. We present the attitudes of local communities towards their involvement in river water management and the sustainable exploitation of natural resources. We administered both open ended and closed structured questionnaires in seven communities in the reservoir catchment. The results revealed that individual residents in these communities have not been involved in the management of the reservoir, adversely affecting goals of sustainable management. Our study concludes with direct policy recommendations and applications in four specific areas to arrive at sustainable management of the facility by involving affected communities through their inclusion in: ongoing and proposed project development as shareholders; the review of existing environmental legislation; adopting of indigenous knowledge in management institutions; and the re-introduction of norms and traditions within the communities.

Chapter 12 - Human-Dominated Rivers and River Management in the Anthropocene

Natural processes and human activities both cause morphological changes in channels. Remote sensing products are often used to assess planform changes, but they tend to overlook vertical changes. However, considering both planform and vertical changes is crucial for a comprehensive evaluation of morphological changes. Using spatiotemporal aerial imagery and topographic data, remote sensing plays a vital role in evaluating channel morphological changes and flood-carrying capacity. This study aimed to investigate the morphological changes of a creek in an urban catchment using very high-resolution remote sensing products. In this study, we developed a new framework for investigating overall channel morphology change by employing very high-resolution aerial imagery and a LiDAR-derived digital elevation model (DEM). By digitizing channel boundaries using ArcGIS Pro 3.0, and analyzing various morphological parameters, erosion, and deposition patterns, we examined the impact of urban expansion and infrastructure development on channel adjustments. Channel adjustments have been performed in the case study catchment (Dry Creek, South Australia, Australia) due to urban expansion and development of infrastructure in the downstream reaches. Our findings revealed a significant southwest shift in the planform of the channel, with a maximum shift of 478 m and an average shift of 217 m since 1998. This alteration resulted in an increase in the sinuosity index reaching 1.2. Over the period from 2018 to 2022, the channel experienced a net deposition depth of 3.4 cm to 3.6 cm in downstream reaches. The annual deposition volume in the downstream reaches was 1963 m3, necessitating regular desilting to prevent channel capacity loss and flooding in the surrounding environment. This study also highlights the incremental growth of riparian vegetation within the channel, which affects surface roughness, channel slope, and carrying capacity. These findings provide a valuable baseline for future investigations into stream channel morphology changes and emphasize the importance of implementing appropriate measures such as desilting and vegetation management to mitigate deposition levels, reduce flood risks, and enhance the overall health and functionality of Dry Creek. The framework used in this study can be applied to other case studies employing reliable and high-resolution remote sensing data products.

The unexpected retreat of riverbanks can significantly influence adjacent infrastructure, floodplain usage, and ecological systems. In our increasingly populated world, where rivers are closely linked with sensitive environments, sudden morphological changes have to be incorporated into planning processes. Changes in the riverbank depend on various factors, including soil composition, pore-water pressure, ship waves, and vegetation. This results in complex erosion mechanisms which are challenging to represent in numerical models. A review of existing studies shows that cohesive banks and the occurring processes, such as the variety of failure mechanisms, the deposition of failed material, or pore-water pressure, are often neglected. This gap limits the predictive accuracy of current models in the case of cohesive banks. Therefore, representing these mechanisms with a 2D model based on the software TELEMAC-2D and considering the random instabilities would enhance the understanding of the morphological development of rivers with cohesive banks. This leads to more accurate predictions and informed decisions that benefit both human activities and ecological systems.

Rivers change the morphology and pattern of their channels in response to environmental changes, a central theme in fluvial geomorphology. However, short‐term changes in channel morphology on the Tibetan Plateau, particularly in response to significant climate change and human activities in recent decades, remain poorly understood. This study examines five reaches of the Parlung Zangbo River, a major tributary of the Yarlung Zangbo River, integrating Landsat remote sensing imagery with hydrological records to analyse changes in channel morphology—including channel width, channel area, braided index and the number and area of mid‐channel bars—between 1973 and 2020. The results indicate that all five sub‐reaches of the Parlung Zangbo River underwent expansion, with significant increases in channel width, channel area, braided index, and both the number and area of mid‐channel bars during this period. However, these changes occurred in distinct phases: an overall expansion of river channels from 1973 to 2000, followed by channel narrowing in the reaches of the Parlung Zangbo River trunk stream between 2000 and 2020. The initial expansion of river channels was likely driven by increased precipitation, meltwater and discharge associated with climate change. In contrast, the decline in precipitation over the southern Tibetan Plateau since 2000 has led to reduced discharge, contributing to channel narrowing. Additionally, upstream of hydroelectric stations, human activities may have altered the riverbed gradient and reduced sediment transport capacity, promoting channel expansion and the deposition of side bars. Among these factors, climate‐related influences, particularly changes in precipitation and temperature, exert the most profound and long‐term effects on river hydrology and channel morphology in the Parlung Zangbo catchment, surpassing the impact of human activities.

The Palliser Triangle of southeastern Alberta and southwestern Saskatchewan is characterized by a variable climate, strong annual moisture deficit, and recurrent drought. Geomorphic systems in such environments are often sensitive to even minor changes in climate. Since climate changes in the twenty-first century are expected to include more frequent drought, geomorphic systems are likely to be affected in ways that threaten sustainable activities in some areas. This review considers four geomorphic systems: eolian, fluvial, mass wasting, and soil redistribution. Soil redistribution integrates a number of lower-level systems, and is of greatest importance with respect to sustainable land management. A qualitative assessment of the potential impacts of four climate change scenarios on each of these geomorphic systems indicates the following: 1. Eolian landscapes are the most sensitive to climatic variability, with the region lying near the threshold of extensive eolian activity. 2. Fluvial systems are the least predictable in terms of response to climate change. 3. Climate influences the frequency of mass wasting processes by modifying the regional groundwater table and determining antecedent moisture conditions. 4. The principal agents of soil redistribution are wind, water, and tillage. Both wind and water erosion are closely related to extreme climatic events. Human activities remain the most critical factors influencing agricultural soils. Identification of possible responses to climate change sets the stage for proactive land management: facilitating rapid adaptation or implementation of mitigation procedures when reliable, long-term regional climatic projections are available, or when trends can be clearly defined through monitoring.

Direct and indirect human disturbances present major challenges to sustainable management of dryland rivers, impacting upon their role as critical lifelines in arid and semiarid regions. This paper presents an overview of changing human–river relations, knowledges and practices in the management of dryland rivers in western India over the last 4500 years. In ancient times, traditional knowledges underpinned local water harvesting techniques that worked with nature. Subsequent imposition of external values and knowledge frameworks in colonial times applied a command‐and‐control ethos that asserted human authority over rivers. Postindependence, development programmes in the second half of the 21st century further accentuated this legacy, with profound implications for river health. Discipline‐bound approaches to river restoration in recent decades have failed to address these concerns. Using the Sabarmati catchment (~20,000 km2) as a case study, we develop a holistic, transdisciplinary approach that integrates traditional place‐based knowledges and practices alongside scientific understandings and the generative potential of Big Data to show how a plural knowledges model can support proactive and precautionary approaches to sustainable river management.

All over the world, including Malaysia, management of rivers is a central issue in this 21st Century. While government has always been traditionally entrusted with the responsibility of managing rivers, increasingly, the public, NGOs (Non‐Governmental Organisations), industrialists, farmers, and other stakeholders are playing a greater role. Sustainable management of rivers involves cooperation between countries and states sharing the same river basin, and cooperation between government and all stakeholders. Internationally, countries need to negotiate and use rivers as the basis for peace rather than conflict. In Malaysia, the Federal Government can initiate policies and remain in charge of governance of rivers, in consultation and cooperation with state governments. However, government must relinquish some of its responsibility on river management to all other stakeholders, viz. industrialists, entrepreneurs, farmers, communities/squatters, NGOs, educational institutions, fishermen, conservationists, tourists, the general public, etc. All stakeholders need to start taking proactive actions, even sacrifices, to manage, protect, conserve and restore our rivers so that their resources can be sustained for future use. This is where people from all levels ranging from politicians, policy makers, private companies, NGOs to individuals can play crucial roles. River management and related river issues need to involve NGOs and the people as these issues happen at the local level. Decision‐making regarding solutions should be carried out at the lowest appropriate level, ideally involving all stakeholders ranging from government to the private sector, NGOs, the local community and schools. People should be the focus both in decision making as well as active “workers” involved with restoration work. The motto of “Malaysia Boleh” (Malaysia Can) involves all Malaysians. This paper discusses how all stakeholders can contribute by working together in smart‐partnerships with government towards effective and sustainable management of rivers in Malaysia.

The article presents general principles of development of the lower Vistula channel in the Holocene period, with a particular emphasis on the unintentional human interference in the fluvial processes associated with deforestation and cultivation of cereals and root crops. It also characterises the basic hydraulic engineering works in the form of construction of embankments, adjustment of the bed and construction of the Włocławek barrage as factors of deliberate human interference and their impact on channel changes. The article characterises morphological and morphodynamic conditions of the basic bed forms, i.e. sandy and gravel bars and pools determining the possibility of river transport, and its development in time and space (depth of navigable route). Perspectives of multi-directional hydraulic development are presented, including the main cascade developments of the lower Vistula. The article presents the opportunities for a comprehensive use of the waterway, which forms route E40 in the section of the lower Vistula, taking into account sustainable development and compensation in the form of restoration of the valley bottom.

3D numerical models are increasingly used to simulate flow, sediment transport and morphological changes of rivers. For the simulation of bedload transport, the numerical flow model is generally coupled with an empirical sediment transport model. The application range of the most widely used empirical models is, however, often limited in terms of hydraulic and sedimentological features and therefore the numerical model can hardly be applied to complex situations where different kinds of morphological processes take place at the same time, such as local scouring, bed armoring and aggradation of finer particles. As a possible solution method for this issue, we present the combined application of two bedload transport formulas that widens the application range and thus gives more appropriate simulation results. An example of this technique is presented in the paper by combining two bedload transport formulas. For model validation, the results of a laboratory experiment, where bed armoring, local scouring and local sediment deposition processes occurred, were used. The results showed that the combined application method can improve the reliability of the numerical simulations.

Land conversions or land use changes also become the main cause of the decline in Citarum River conditions. The relationship between river sustainability and its watershed carrying capacity plays a vital role in protecting watersheds to implement sustainable water resources management. Previous studies on river assessment for watershed management have predominantly focused on specific hydrological and/or technical results, rather than considering the process of the development of carrying capacity methodology due to land-use types. Motivated by this fact, the objective of this study is to develop a simplified carrying capacity methodology due to land-use types for sustainable river management by selecting the Upper Citarum Watershed (a main part of Citarum Watershed) located in West Java Province, Indonesia as an example of a study area. The conceptual framework development for watershed carrying capacity due to land-use types was designed the step-by-step methodology standard regarding the sustainable river management. The methodology of this study also used AHP method consisting of screening and selecting attributes, transforming and developing sub-indices, assigning weights, and formulating a runoff cumulative (Ccum) to examine standards and criteria for carrying capacity classification due to the changes of land-use types. The analysis revealed a significant change in the proportions of the various land use types of the study area. The conclusion is it integrates the measures of selected important land-use types to create a single dimensionless number of runoff cumulative and its classification, and a modified approach to communicate information on river status to the public and related policy makers. To advance future studies, it is necessary to develop a comprehensive evaluation and monitoring systems by using GIS-based spatial and temporal analysis.

The Living Lab approach has become popular and developed in the past decade. It could provide a configuration to pursue a shared vision of integrated water resources management of the Citarum River in West Java - Indonesia. The multi-stakeholder situation and the growing recognition of interdependencies among stakeholders foster the complexity of addressing sustainable river management for the Upper Citarum River. To gain insights on essential competencies and adaptations in higher education curricula, the Environmental Engineering Department of the Faculty of Civil and Environmental Engineering-ITB, Telkom University Indonesia, and Van Hall Larenstein University of Applied Sciences, Netherlands, joined hands in a collaborative research project. This study aims to develop a socio-engineering aspect for sustainable river water quality management in the Environmental Engineering Field and Curricula. The methods used are social imaginaries of Participatory Mapping and a Poetry Route that allowed the involved river bank communities to activate their role and take positions in the living lab. Institutional stakeholders, acting in a facilitating role, learned to gain and share information from and with the community. The result concludes that social imaginaries methods enable a new perspective in developing community-based programs and advocate further exploring the socio-engineering competencies of environmental professionals.

1. Sustainable river management demands a strategic approach that renders even routine decisions highly complex if they are to be consistent, transparent and accountable. Under these circumstances, there is an increasing need for decision-support systems, although carefully structured guidelines and statements of best practice will continue to play a major supporting role. 2. This support is likely to be particularly important in wide-ranging contexts, from routine decisions in determining land drainage consents, to complex decisions involving significant uncertainty. Sustainable Upland River Corridor Management Evaluation System (SURCoMES) has been developed as a prototype system to demonstrate the potential scope and problems for providing decision support in complex and uncertain scenarios. 3. In its present form it focuses on the selection of management responses to problems of river bank erosion. It caters for uncertainty by providing guidance as to whether a particular decision is more or less sustainable than alternative options. It does not determine whether actions are absolutely sustainable or not. 4. Because of the judgemental nature of the questions, underlying criteria and standards have been built into the system. These evaluations, are, in part, subjective, even when based on existing best practice and experience, so a Delphi technique approach has been used to capture professional opinion from the research sector and the Environment Agency which is responsible for river management in England and Wales. 5. Decision support will undoubtedly have an important future in sustainable environmental management. The SURCoMES approach indicates potential applications, but the system requires further development and validation before it is implemented more widely.

Flow Regulation by Dams: Ongoing and Emerging Trends

<p>Geomorphic systems are affected by climate forcing and sediment supply. Due to non-linear relationships of forcings and sediment mobilization, it is debated whether environmental signals are preserved in such systems, or if they are rather dampened or shredded in the sediment output. Tracing the cause and effect in such systems is commonly impossible to do from observations alone. Therefore, numerical models are interesting to study geomorphic system behavior. We use a modeling chain consisting of the SedCas sediment cascade model (Bennett et al., 2014; Hirschberg et al., 2021) and the AWE-GEN stochastic weather generator (Fatichi et al., 2011), which has been calibrated for a debris-flow catchment in the Swiss Alps, the Illgraben, and used for climate change impact assessment (Hirschberg et al., 2021). Here we use this modeling setup to study the long-term behavior of such a system under consideration of different mean erosion rates and sediment production mechanisms. This numerical experiment is unique because we conducted simulations at high temporal resolution (hourly) while also spanning geological time scales (10k years).</p><p>We show that the analysis of short sediment records is characterized by high uncertainties and that especially supply-limited systems are at risk to have underestimated mean sediment. This is in concert with field observations on short- and long-term erosion rates from other basins, and can be attributed to transient hillslope sediment supply to the channel. Furthermore, we demonstrate how large hillslope landslides, or the absence of sediment supply, introduce long-term memory effects which can be quantified in the sediment yield. This long-term memory increases uncertainty and reduces interannual variability in annual sediment yields. Interestingly, details of the actual timing of sediment supply events are shredded and have no discernible impact on sediment yields at the outlet. The study highlights the need of characterizing variability in erosional events with regard to their stochastic nature. Furthermore, these results will corroborate the analysis of erosion rates, support decision making and decrease the risk of misinterpretation both in natural hazard and climate change impact assessment, especially if they are based on short records.</p><p> </p><p>REFERENCES</p><p>Bennett, G. L., P. Molnar, B. W. McArdell, and P. Burlando (2014), A probabilistic sediment cascade model of sediment transfer in the Illgraben, Water Resour. Res., 50, 1225– 1244, doi:10.1002/2013WR013806.</p><p>Fatichi, S., Ivanov, V. Y., & Caporali, E. (2011). Simulation of future climate scenarios with a weather generator. Advances in Water Resources, 34(4), 448-467.</p><p>Hirschberg, J., Fatichi, S., Bennett, G. L., McArdell, B. W., Peleg, N., Lane, S. N., et al. (2021). Climate change impacts on sediment yield and debris- flow activity in an Alpine catchment. Journal of Geophysical Research: Earth Surface, 126, e2020JF005739. https:// doi.org/10.1029/2020JF005739</p>