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In this paper, a natural headland bypassing is investigated in terms of its short (months to years) and long-term (years to decades) variability and its relationship with wave conditions, climate drivers and anthropogenic interventions. The research is focused on Fingal Head (New South Wales, Australia) where nine detailed topo-bathymetric surveys were undertaken between June 2018 and January 2020. To extend the analysis in time, over 30 years of satellite and aerial images were used to describe the headland bypassing variability based on the shoreline and sandbar position changes. Shoreline and sandbar positions presented moderate to strong correlation between updrift and immediate downdrift of the headland highlighting the influence of the bypassing process for the longshore transport on the study area. Results indicate that the headland bypassing around Fingal Head is governed by two distinct processes and their dominance is controlled by waves and sediment availability. The sandbar-driven bypassing scenario requires a storm wave event to trigger the sandbar system and over seven months to complete the full bypassing cycle. A quicker bypassing cycle (i.e. few months) happens when sediment leaks around the headland following a persistent low energy wave condition that largely accretes the updrift upper beach. Headland bypassing cycles occur in multiple timescales, including seasonal variability of the wave climate to interannual and decadal cycles of shoreline progradation and retreat. Shifts in the large-scale climate drivers such as El Niño-Southern Oscillation, Pacific Decadal Oscillation and Interdecadal Pacific Oscillation were observed to influence on changes to the low frequency of variability of the headland bypassing in the study area by affecting the predominant wave direction and updrift beach sand availability. The understanding of this intermittent nature of the headland bypassing process and particularly considering its periodicity and the related driving forces is crucial to predict future coastal hazards and develop management strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Beach–dune systems are highly dynamic features of the coastal system, the evolution of which is influenced by several processes that occur at very different spatial and temporal scales. To mitigate shoreline retreat that threatens extensive coastal areas worldwide, coastal erosion mitigation measures are implemented, aiming to make coastal areas resilient to the effects induced by coastal erosion and the anticipated climate change related to storms, flood events and sea level rise. Numerical modelling can support planned and sustainable coastal management from a medium-to-long-term perspective (decades). This research focuses on presenting contributions regarding the numerical modelling of subaerial beach dynamics (berm width and dune systems interactions) from a medium-term perspective. The method applied is based on a combination of the results of two simplified numerical models (the LTC and CS-Model). The results demonstrate the potential of the proposed combined model for medium-term projections, allowing for the interpretation of beach–dune dynamics and the evaluation of the importance of longshore and cross-shore sediment transport processes. [ABSTRACT FROM AUTHOR]

The sediment transport along a coastal zone of Thermaikos Bay and the interaction with the coastline were studied in the present research. This study concerns the greater basin of an existing breakwater, for which the sand transport during the time periods 1950–1968 and 2009–2017, before and after the construction of the breakwater, were examined. The breakwater led to sand accumulation behind it, causing the well-known phenomenon of salient. It was revealed that climate change, in terms of wind conditions, significantly affected sediment transport; more specifically, the sand transport during 2009–2017 not only decreased significantly, but also changed its direction, in relation to 1950–1968. Based on the information obtained, technical interventions are proposed for the interception of sediment transport and the consequent accumulation of sand behind the breakwater. [ABSTRACT FROM AUTHOR]

The densely populated coast of the Gulf of Guinea (GoG) is experiencing escalating erosion from climate change (CC). To assess Longshore Sediment Transport (LST) changes in the past and future, an empirical formula was used to model the GoG's LST. Nearshore wave conditions, crucial for LST estimation, were derived by projecting significant wave height, mean wave period, and mean wave direction from deep water to the breaker zone. These wave conditions were used as input for LST computation. Analysing three time slices: Past (1979–2005), mid-century (2026–2045), and end-century (2081–2100) under RCPs 4.5 and 8.5, results indicate continuous increase in LST in most locations, with local and seasonal variations. LST magnitudes range from 104 to 105 m3y−1 in the GoG, with the Cameroonian coast having the least. This aligns with the rising wave energy from CC. LST directions are predominantly eastward, though some locations, like off Lagos and Cameroon-Gabon coasts, show westward trend, correlating with coastal orientation influenced by southward wave directions. RCP 8.5 projections suggest mid-century increase, intensifying by end of century, with yearly rates of change around 103 m3y−1 and future LST changes up to 105 m3y−1. This situation implies accelerated sediment removal, heightening erosion. [ABSTRACT FROM AUTHOR]

Makhool Dam is a proposed structure on the Tigris River in the Salah al-Din Governorate, northwest of Baiji. The reservoir's sediment sources encompass the Tigris River, the Greater Zab River, and the Lesser Zab River. Climate change exerts a significant influence on both sediment accumulation within the dam reservoir and associated water resources. This paper specifically investigates the impact of climate change on sediment dynamics within the Makhool Dam reservoir. HEC-RAS 6.3.1 has been used to simulate the sediment dynamics and flow for the three rivers entering the reservoir. The SSP2-4.5 and SSP5-8.5 emission scenarios were applied to the 2021-2040, 2041-2060, 2061-2080, and 2081-2100 of 2021–2100. The calibration process of the model was performed using recorded water surface elevation measurements. The model was validated using the sediment concentrations at the proposed Makhool Dam. The sediment mass decreases along the rivers from upstream to downstream. The sediment mass is anticipated to decrease by approximately 20% and 35% from 2021 to 2100 under the SSP2-4.5 and SSP5-8.5 scenarios, respectively. For the studied future period, the estimated annual sediment deposition under the SSP2-4.5 and SSP5-8.5 scenarios is around 22×106 tons and 19×106 tons, respectively. In addition, under these scenarios, the potential life of the Makhool Reservoir is expected to be 95.7 and 109.5 years, respectively. The findings of this paper can play a vital role in supporting planners and decision-makers in performing efficient strategies for climate change adaptation and mitigating the impact of climate change.

The Rhine River is affected by major human interventions affecting its morphology and sediment regime, which have severely changed its flow and sediment transport. While channelization has increased the sediment transport capacity in the free-flowing sections, the sediment retention behind dams has caused a bedload deficit downstream and has additionally intensified riverbed erosion. The resulting consequences range from the exposure of less erodible sediment layers that pose obstacles for navigation, to the scouring of infrastructure, the lowering of groundwater levels, and multiple negative ecological consequences. To optimize the efficiency of countermeasures, a coherent overview of all sediment-related activities and the state of knowledge on the Rhine catchment is required. That is why the present study aims to give a catchment-wide overview in this regard, identify knowledge gaps and proposing a future research programme. The methodological approach includes a comprehensive literature review and online interviews with experts from six riparian countries working in the fields of sediment research and management. Based on our investigations, we have derived several research topics, each consisting of research questions. Three project ideas were defined that should primarily be realized: (i) the influence of climate change and land use change on the sediment regime; (ii) alteration and improvement of the sediment balance and continuity, sediment transport, and morphology; and (iii) national and bilateral projects on sediment transport processes and management. [ABSTRACT FROM AUTHOR]

This study identifies and summarizes potential risks to operations, regulatory compliance, supply chains, and infrastructure of the electric power industry from changing surface water conditions resulting from global climate change. The results help inform companies/utilities seeking to incorporate climate change risk in their planning and decision‐making processes by ranking risk severity and likelihood of occurrence on both a regional basis and by risk receptor. The assessment includes identification of potential risks to: (1) thermal generating, (2) hydroelectric, (3) land‐based renewable generating, and (4) transmission and distribution assets. These risks may result from such projected changes as reduced water availability (e.g., for hydroelectric or once‐through cooling), increased water temperatures (e.g., decrease in cooling efficiency, inability to meet discharge permit conditions), increased flood severity (e.g., increased streambank erosion and/or damage to river‐adjacent infrastructure), and decreased water quality (e.g., from increased transport of sediment and dissolved solids). The potential risks identified from this qualitative risk‐assessment are documented in a graphical format depicting both severity and likelihood. This approach allows for comparison of risks across a portfolio and for future prioritization of adaptation strategies. A total of 32 risks were identified in the study, including nine risks to infrastructure, six risks to operations, four risks to supply chain, and 13 environmental/regulatory risks. [ABSTRACT FROM AUTHOR]

This research investigates the impact of climate change on the geopolitical dynamics of South Asia, focusing on India, China, and Bangladesh, which share the Brahmaputra River basin. The changing climate significantly affects these nations, with the political landscape of South Asia playing a crucial role in shaping regional dynamics. The Brahmaputra River basin is vulnerable to climate-induced challenges, such as altered river flow, increased flooding, and changes in sediment transport, which impact water resources and infrastructural development, influencing the social and economic well-being of the populations in these countries. Utilizing a multidisciplinary approach, the study combines climate models, hydrological data analysis, and geopolitical assessments to evaluate the effects of climate change on the Brahmaputra River basin and its implications for regional cooperation and conflict. The findings reveal that climate change exacerbates existing waterrelated challenges, leading to heightened flood risks, disrupted sediment transport, and strained water resources, threatening socio-economic stability. The research underscores the urgent need for collaborative strategies to address these impacts, emphasizing the importance of integrated water resource management to mitigate geopolitical tensions and promote regional stability. [ABSTRACT FROM AUTHOR]

Climate change and human activities exert significant influence on the water–sediment relationship in arid and semi-arid regions. Therefore, comprehending the underlying mechanisms is crucial for the effective management of water and soil resources, as well as integrated watershed management. This research focuses on the Kuye River watershed (KYH_W) in the middle reaches of the Yellow River in China, along with its sub-watersheds Wangdaohengtazi (WDHT_SW) and Xinmiaosi (XM_SW). This paper utilizes the Mann–Kendall non-parametric test and the double cumulative curve method to examine the interannual trends of runoff, sediment transport, precipitation, temperature, and NDVI factors. Furthermore, the method of the slope change ratio of cumulative quantity (SCRCQ) is utilized to quantitatively evaluate the impacts and contribution rates of climate change and human activities on water–sediment changes within each watershed. The results are as follows: (1) From 1969 to 2019, the entire watershed experienced a significant decrease in both runoff and sediment transport, with 1997 marking the year of abrupt change. However, following 2012, the KYH_W and WDHT_SW exhibited a noticeable rebound in runoff. (2) Human activities predominantly contribute to the reduction in water and sediment in the watershed. (3) After the abrupt change, between 1998 and 2011, the contribution rates of climate change and human activities to the annual runoff reduction in the entire KYH_W reached 33% and 64%, respectively. Moreover, these rates for sediment transport reduction reached 26% and 74%, respectively. Subsequently, after 2012, the contribution rates of both factors to the increase in watershed runoff reached 29% and 71%, respectively. Factors other than the NDVI, within human activities, played a dominant role in augmenting the watershed's runoff. (4) Prior to 2011, changes in vegetation cover resulting from the Grain for Green Program, as measured by the NDVI, emerged as the primary factor responsible for reduced runoff in the watershed. Conversely, factors other than the NDVI assumed dominance in reducing sediment transport. The SCRCQ method offers a quantitative approach to assessing water–sediment changes. Based on this method, the study further underscores the substantial impacts of climate change and human activities on variations in runoff and sediment transport within the KYH_W in the middle reaches of the Yellow River. Notably, the water–sediment changes in the KYH_W exhibit distinct stage-wise and spatial discrepancies, which warrant increased attention in future research endeavors. [ABSTRACT FROM AUTHOR]

Developed barrier systems (barrier islands and spits) are lowering and narrowing with sea‐level rise (SLR) such that habitation will eventually become infeasible or prohibitively expensive for most communities in its current form. Before reaching this state, choices will be made to modify the natural and built environment to reduce relatively short‐term risk. These choices will likely vary substantially even along the same developed barrier system as these landscapes are rarely uniformly managed alongshore. Building on the results from a companion paper, here we use a new modeling framework to investigate the complexities in barrier system dynamics that emerge as a function of alongshore variability in management strategies, accelerations in SLR, and changes in storm intensity and frequency. Model results suggest that when connected through alongshore sediment transport, barriers with alongshore variable management strategies—here, the construction of dunes and wide beaches to protect either roadways or communities—evolve differently than they would in the absence of alongshore connections. Shoreline stabilization by communities in one location influences neighboring areas managed solely for roadways, inducing long‐term system‐wide lags in shoreline retreat. Conversely, when barrier segments managed for roadways are allowed to overwash, this induces shoreline curvature system‐wide, thus enhancing erosion on nearby stabilized segments. Feedbacks between dunes, storms, overwash flux, and alongshore sediment transport also affect outcomes of climate adaptation measures. In the case of partial, early abandonment of roadway management, we find that system‐wide transitions to less vulnerable landscape states are possible, even under accelerated SLR and increased storminess. Plain Language Summary: Because humans inhabit barrier islands and spits (collectively referred to as "barriers") these landscapes, that would otherwise naturally change shape in response to storms and sea‐level rise (SLR), are influenced by efforts to protect development with wide beaches and tall dunes. These features interfere with a process called overwash, which transports sand landward during storms, building barrier elevation relative to sea level. Here, we use a new model to better understand how these interactions influence the habitability of barriers over time. Our simulations show that different management decisions made for adjacent coastal segments affect each other in positive and negative ways. When communities nourish beaches, adjacent to segments managed for roadways, some nourished sand reaches the adjacent segments, reducing shoreline erosion there. Conversely, portions of barriers that are managed only for roadways allow some overwash to reach the barrier interior; this negatively affects neighboring communities by enhancing their shoreline erosion rates. We find that early abandonment of dune management along portions of barriers may prevent highly vulnerable future states, such as barrier drowning. As communities explore choices for climate adaptation, our findings reveal the importance of coordination among decision makers in adjacent communities to avoid undesirable outcomes. Key Points: When management strategies vary alongshore, their effects are coupled via alongshore sediment redistribution, influencing barrier evolutionBeach nourishment (along portions of barriers) induces system‐wide lags in shoreline retreat, even decades after nourishment practices ceaseMore overwash (due to lower dunes or increased storminess) can prolong habitability, but drives increased nourishment frequency elsewhere [ABSTRACT FROM AUTHOR]

Atolls islands are biogenic landforms that are intrinsically capable of adjusting their size, position, and elevation to changing sea levels. The vulnerability of atoll islands to sea level rise is not intrinsically due to their low elevation but primarily due to the loss of their island building capacity. The geophysical processes that control atoll island accretion are being impacted on global and local scales. Protecting and restoring the natural geophysical processes of atoll island accretion through local conservation actions is key to unlocking nature-based opportunities for enhancing atoll resilience to global change. Atoll islands are often perceived as inevitably lost due to rising sea levels. However, unlike other islands, atoll islands are dynamic landforms that have evolved, at least historically, to vertically accrete at a pace commensurate with changing sea levels. Rather than atoll islands' low elevation per se , the impairment of natural accretion processes is jeopardising their persistence. While global marine impacts are deteriorating coral reefs, local impacts also significantly affect accretion, together potentially tipping the scales toward atoll island erosion. Maintaining atoll island accretion requires intact sediment generation on coral reefs, unobstructed sediment transport from reef to island, and available vegetated deposition sites on the island. Ensuring the persistence of atoll islands must include global greenhouse gas emission reduction and local restoration of accretion processes. [ABSTRACT FROM AUTHOR]

Shorelines face growing threats due to climate change and diminishing sand supply. Coastal headlands, common rocky features along coastlines, are crucial in shaping hydrodynamics and sediment transport. Yet, the influence of future climate conditions, including sea‐level rise (SLR) and intensified storm energy on complex shorelines with headlands has remained relatively unexplored. In this study, we model changes in hydrodynamics and headland bypassing under different SLR and higher storm wave scenarios. Our findings reveal the formation of circulation cells on both sides of a headland, where wave energy converges around the headland zone. Future climate conditions result in larger storm waves on the beach. However, SLR enhances nearshore currents through a landward shifting of the circulation cells, while higher storm waves intensify offshore flow currents due to the seaward movement of the cells. This effect, in turn, increases the potential for headland sediment bypassing. Plain Language Summary: Coastal headlands, prominent rocky features along open coastlines, play a crucial role in protecting nearby beaches from strong waves and erosion. They also affect how sand is exchanged between different beaches. We use a model to explore how future climate conditions including sea‐level rise (SLR) and larger storm waves influence coastal waves, littoral currents, and the transport of sand around headlands. Our findings reveal that headlands converge wave energy forming circulation flow cells. SLR results in stronger nearshore currents, driven by the landward movement of the rotating flow cells. In contrast, larger storm waves can move the rotating flow cells seaward, thereby increasing offshore current strength and the potential for sand transport around the headland. Understanding how coastal waves, flow and sediment transport change under future climate conditions will help determine coastal resilience. Key Points: The formation of circulation cells and wave energy convergence around headlands during storms reduce bottom shear stress at the beachSea‐level rise increases wave heights, currents, and bed shear stress in the nearshore because of landward shifting of the circulation cellsHigher storm waves expand the surf zone, shift circulation cells seaward, and enhance potential headland sediment bypassing [ABSTRACT FROM AUTHOR]

This paper investigates how variations in sediment supply, grain size distribution and climate change affect channel morphology and flood inundation in the Nakkhu River, Kathmandu, Nepal. Climate change‐induced extreme rainfall is expected to increase flood intensity and frequency, causing severe flooding in the Kathmandu basin. The upper reaches of the Nakkhu River are susceptible to landslides and have been impacted by large‐scale sand mining. We simulate potential erosion and deposition scenarios along a 14 km reach of the Nakkhu River using the landscape evolution model CAESAR‐Lisflood with a 10 m digital elevation model, field‐derived sediment grain size data, daily discharge records and flood forecast models. In a series of numerical experiments, we compare riverbed profiles, cross‐sections, flood extent and flow depths for three scenarios (1.2‐, 85‐ and 1000‐year return period floods). For each scenario, the model is first run without sediment transport and then with sediment transport for three grain size distributions (GSDs) (observed average, finer and coarser). In all cases, the inclusion of sediment led to predicted floods of a larger extent than estimated without sediment. The sediment grain size distribution was found to have a significant influence on predicted river morphology and flood inundation, especially for lower magnitude, higher probability flood events. The results emphasise the importance of including sediment transport in hydrological models when predicting flood inundation in sediment‐rich rivers such as those in and around the Himalaya. [ABSTRACT FROM AUTHOR]

Natural hazard is recognized to be a threat to human society that is becoming more critical under the perspective of climate change. Italy is one of the most exposed European countries to hydrogeomorphological hazard, as proven by the annual casualties and economic losses. Among the most recent events, the one happened in the Misa river catchment in 2022 is of particular interest for the great amount of rainfall poured in just one night, which led to extensive erosion. The mountainous part of the catchment was hit by several landslides, and the resulting sediments and debris, transported downstream by rivers, increased the amount of damages. This event was interpreted as directly caused by climate change, as it was linked to a tropical storm not common at this latitude. This work proposes an analysis of this exceptional event from a hydrological point of view. The 2022 event was compared with other relevant events from the past, in order to evaluate the peak discharge, the sediment erosion and transport processes in the area for different scenarios. The analysis included the modelling at catchment scale with two physically-based models: SWAT, which provides results on channel processes, and SMART-SED, working at the catchment scale. The two scales of analysis, together with field surveys, gave a better understanding of the evolution of the shallow processes during the events. Finally, this work intends to highlight the relevance of hydrological modelling for the management of hazard in different scenarios at catchment scale. [ABSTRACT FROM AUTHOR]

Climate change affects cryosphere-fed rivers and alters seasonal sediment dynamics, affecting cyclical fluvial material supply and year-round water-food-energy provisions to downstream communities. Here, we demonstrate seasonal sediment-transport regime shifts from the 1960s to 2000s in four cryosphere-fed rivers characterized by glacial, nival, pluvial, and mixed regimes, respectively. Spring sees a shift toward pluvial-dominated sediment transport due to less snowmelt and more erosive rainfall. Summer is characterized by intensified glacier meltwater pulses and pluvial events that exceptionally increase sediment fluxes. Our study highlights that the increases in hydroclimatic extremes and cryosphere degradation lead to amplified variability in fluvial fluxes and higher summer sediment peaks, which can threaten downstream river infrastructure safety and ecosystems and worsen glacial/pluvial floods. We further offer a monthly-scale sediment-availability-transport model that can reproduce such regime shifts and thus help facilitate sustainable reservoir operation and river management in wider cryospheric regions under future climate and hydrological change. [ABSTRACT FROM AUTHOR]

• The overall impact of all the large dam-reservoir systems on the sediment fluxes at the delta scale was quantified. • Long-term datasets of daily water discharges and suspended sediment concentrations were analyzed. • The Red River system experienced two notable declines in sediment load in 1988 and 2009. • The annual sediment load has dramatically decreased by about 91% from the 1950s to 2021. • The decrease in sediment load is mainly attributable to a series of dam-reservoirs operating upstream. The sediment regime of the Red River system, the second largest in Vietnam, has undergone changes since the implementation of dams and reservoirs, with implications for downstream river processes. We analyzed long-term datasets of daily discharge and suspended sediment concentrations collected at key gauging stations downstream of the three main tributaries: HB on the Da River, YB on the Red River (main channel), VQ on the Lo River, and ST, the outlet of the Red River system. The results indicated a sharp reduction in the annual sediment load transported by the Red River system, as observed at the four stations. For example, at the ST station, there was a dramatic decline of 91% in sediment load, dropping from 117.9 × 106 ton/yr in the period 2009–2021 to 10.5 × 106 ton/yr in the period 1958–1987. The Red River system experienced two notable declines in sediment load. The first decline occurred from 1988 to 2008, which can be attributed to the commencement of Hoa Binh dam's operation in 1988. The second decline has taken place since 2009, coinciding with the utilization of new dam-reservoirs. Meanwhile, an abrupt change in water discharge was observed clearly since the end of 2008 at all four stations. However, the reductions in water discharges were found to be less pronounced when compared to the sediment budget. Based on our analysis, we concluded that the impacts of dam-reservoirs have had a more substantial influence on the system compared to variations in climate, such as air temperature and precipitation. [ABSTRACT FROM AUTHOR]

During their flow through an area, the streams are used to erode, transport and re-deposit sediments in the number of cycles following the climatic variation in an area. This cycle in turn affect the chemistry of these sediments and hence the geochemical study of these sediments helps to understand the palaeo-climate, source-area weathering and provenance of the study area. In order to understand the geochemical classification of sediments, palaeo-climate, source-area weathering and provenance for stream sediments of the Eastern Ghats Mobile Belt (EGMB), 364 stream sediment samples were collected from the area around Daringbadi, Kandhamal district, Odisha, India and analyzed for major oxides, trace elements and rare earth elements. These sediments are geochemically classified as shaly and wacke type, moderately mature and derived through the high intensity of weathering of source rock under warm and humid climatic condition. The positive correlation between Al2O3 and Fe2O3, MnO, and MgO, indicates multiple sources for sediment and these oxides are associated with clay minerals. The discrimination function diagram suggests a felsic igneous as well as quartzo-sedimentary provenance for these sediments whereas the ratio of Al2O3/TiO2 and concentration of V-Ni-Th suggest a felsic igneous source rock. The high concentration of LREE, slight enrichment of HREE and negative Eu anomaly indicate terrestrial or continental crust source rock. Hence the source rock for these sediments are granite gneiss, charnokite and khondalite present in and around Daringbadi area. [ABSTRACT FROM AUTHOR]

Scour is a phenomenon that affects structures deployed in rivers or seas, favoring the transport of sediments around their foundations, which can expose their structural stability. This work aimed to develop a physical model of a mobile bottom to determine the scour-hole extensions around a group of four vertical piles of circular sections subjected to irregular waves. For this purpose, a beach profile and a typical slope were constructed and subjected to 24 h of storm waves, divided into 12 h intervals in the prototype. Additionally, three wave periods were studied according to the Mexican Institute of Transportation wave data and three scenarios of a rise in sea level. The data suggest that the length of the scour hole was greater in the piles in the front for all cases, which may be reflected in a reduction in scour protection costs. The results obtained for the extent of the scour hole suggest a setting of less than four times the pile diameter in most cases. Finally, it is inferred that a rise in sea level by itself is not a decisive factor in the increase in the values obtained; therefore, it is necessary to consider the variations in wave heights and wave periods associated with such increases. [ABSTRACT FROM AUTHOR]

The morphology of tide‐dominated systems is progressively influenced by human activities and climate change. Quantitative approaches aiming at understanding or forecasting the effects of interventions and climate change are often aggregated, thereby simplifying or schematizing the investigated area. In this work, we advance on the knowledge of sediment transport processes shaping tidal systems and on methodologies translating schematized model output into physically realistic variables. In terms of improved physics, we systematically evaluate the influence of sand‐mud interaction processes. Most tidal systems are shaped by a mixture of sand and mud. Morphological models typically compute transport of sand and mud independently, despite studies clearly demonstrating that their physical behavior is mutually dependent. We investigate the effects of two interaction mechanisms (erosion interaction and roughness interaction, applied with varying mud erodibility) with a schematized process‐based morphodynamic model. We convert model output into metrics that describe the meso‐scale configuration of the modeled systems, allowing a quantitative comparison of scenarios. Modeled patterns and intertidal flat shape, size and composition widely vary with mud erodibility settings, but equally depend on the evaluated sand‐mud interaction mechanisms (with erosion interaction having a larger effect than roughness interaction). Sand‐mud interaction thus needs to be accounted for from a physical point of view, but also to improve predictions of tidal basin evolution models, particularly the (bimodally distributed) sediment composition of intertidal flats. Plain Language Summary: Human interventions and climate change are progressively influencing the state of coastal systems. Their impact on coastal evolution takes place on decades to centuries and the present‐day modeling tools have limitations to study these impacts. Models with highly schematized configurations have often been used in the past to increase our understanding of coastal evolution. We advance on this, by determining the effect of sand‐mud interaction on the modeled long‐term evolution of tidal basins. The bed of most tidal basins is composed of two sediment types: sand and mud. From previous research, it is known that sand and mud do not behave independently. We investigate the effects of two interaction mechanisms (erosion and roughness interaction) using a model with a schematized configuration in terms of topology and forcing, but including the most relevant physical processes. To quantitatively compare the output of different model scenarios, we translate the results into a number of metrics. Our results reveal that sand‐mud interaction processes (particularly erosion interaction) influence tidal basin evolution. Including sand‐mud interaction can significantly improve modeling results, especially the sediment composition of intertidal flats. We present guidelines that can be followed to improve models depending on the real‐life system they should compare to. Key Points: Sand‐mud interaction largely impacts long‐term morphodynamic evolution of intertidal areas in tidal systemsAccounting for sand‐mud interaction in morphodynamic models is crucial to reproduce the observed bimodal distribution of the mud contentSchematized model results should be parameterized for validation and comparison with real systems [ABSTRACT FROM AUTHOR]

Human activities and climate are two key factors affecting hydrological and soil erosion processes. Understanding their impacts on water discharge and sediment transport is very important for sustainable development of watersheds, particularly in subtropical regions with high precipitation and high sediment loads. We here compared the long-term dynamics of water discharge and sediment transport in four large contiguous watersheds in subtropical China and explored the importance of the main influencing factors including climate, nature endowment such as geology, and human activities. Significant differences have been observed between watersheds in terms of sediment and water discharge (p

A prevalent engineering task in practice is calculating the annual balance of sediments on some watercourses. This is particularly challenging when assessing the backfilling of river reservoirs that have a multifunctional purpose. Trakošćan Lake was built in the period from 1850 to 1862 as a pond and landscape addition to the park and Trakošćan castle. After 60 years, the lake was drained in 2022, and the work began on sediment excavation to improve the lake's ecological condition due to about 200,000 cubic meters of deposited silt in the lake. In this research, the annual sediment production is calculated for the long-term period 1961–2020, based on empirical parametric methods (Fleming, Brunne). The results are compared with results from previous projects and recent sediment deposit investigations. Since there are no changes in LC/LU on this natural catchment, the decreasing trends in long-term sediment transport were compared with meteorological values, daily rainfall, and snow days. It is concluded that the intensity characteristics of the rainfall should be investigated more in detail and could provide much more tangible information regarding climate change impacts. Some targets for future monitoring design and research techniques are set. [ABSTRACT FROM AUTHOR]

Hydrological connectivity plays a major role in solving water resource and eco-environmental problems. However, this phenomenon has not been afforded the attention it deserves. The detailed analysis of connectivity in river systems could provide considerable insight into the structural and functional attributes of riverine landscapes. The current study used a graph theory approach and associated connectivity indicators to explore the characteristics and evolution of river systems and hydrological connectivity in a large catchment (Poyang Lake, China). The results revealed that the structure of the river system tended to be complex during 1990–2020, characterized by a dynamic evolution of tributaries in certain northern areas. Both river density and complexity exhibited an increasing trend by up to 15%, with the change rate after 2000 approximately twice as high as that of the preceding period. Overall, human activities across the catchment were more likely to play a key role in leading to significant changes in the quantity, morphometric, and structural characteristics of the river system. Additionally, the functional connectivity analysis indicated that the index of connectivity (IC) in the downstream catchment was stronger than that of the upstream vegetation areas, suggesting a strong contribution to the runoff sediment transport (r = 0.6–0.7). This study highlights the spatial and temporal evolution of both structural and functional connectivity in the large Poyang Lake catchment. The findings of this work will benefit future water resource management and applications by providing a strategy for protecting the surface hydrology and mass transport of large river basins under climate and land use changes. [ABSTRACT FROM AUTHOR]

River profiles are shaped by climatic and tectonic history, lithology, and internal feedbacks between flow hydraulics, sediment transport and erosion. In steep channels, waterfalls may self‐form without changes in external forcing (i.e., autogenic formation) and erode at rates faster or slower than an equivalent channel without waterfalls. We use a 1‐D numerical model to investigate how self‐formed waterfalls alter the morphology of bedrock river longitudinal profiles. We modify the standard stream power model to include a slope threshold above which waterfalls spontaneously form and a rate constant allowing waterfalls to erode faster or slower than other fluvial processes. Using this model, we explore how waterfall formation alters both steady state and transient longitudinal profile forms. Our model predicts that fast waterfalls create km‐scale reaches in a dynamic equilibrium with channel slope held approximately constant at the threshold slope for waterfall formation, while slow waterfalls can create local channel slope maxima at the location of slow waterfall development. Furthermore, slow waterfall profiles integrate past base level histories, leading to multiple possible profile forms, even at steady‐state. Consistency between our model predictions and field observations of waterfall‐rich rivers in the Kings and Kaweah drainages in the southern Sierra Nevada, California, supports the hypothesis that waterfall formation can modulate river profiles in nature. Our findings may help identify how bedrock channels are influenced by waterfall erosion and aid in distinguishing between signatures of external and internal perturbations, thereby strengthening our ability to interpret past climate and tectonic changes from river longitudinal profiles. Plain Language Summary: Mountain rivers are shaped by tectonic and climatic forces; thus, the longitudinal profile of a river (a plot of river elevation vs. distance along the stream) can be used to investigate geologic history. Abrupt changes in river slope are often interpreted as signals of an external tectonic or climatic disruption. However, other factors may disrupt longitudinal profiles, including changes in rock type and differences in river erosion processes. Here, we investigate one such process: waterfalls formed by feedbacks between water flow, sediment transport and river‐bed erosion, and whether these waterfalls can alter longitudinal profiles without climatic or tectonic changes. We make a model to investigate what river profiles might look like if waterfalls naturally develop and alter erosion rates in all channels exceeding a specific slope threshold. Our model predicts that waterfalls generate distinct river profile features including a constant channel slope maintained over several kilometers where waterfalls occur and sharp increases in slope due to waterfall occurrence, both of which we have found in waterfall‐rich rivers in the southern Sierra Nevada, California. This research identifies similarities and differences between the impact of changes in tectonics and climate versus internal feedbacks such as self‐formed waterfalls on river profiles. Key Points: We investigate how erosion via self‐formed waterfalls alters river long profile form using a stream power model with a slope thresholdSelf‐formed waterfalls alter fluvial relief and concavity, create dynamic equilibriums, and, in cases, path‐dependent profile formsProfiles of rivers in the Sierra Nevada, California, with abundant waterfalls have similar features to our model [ABSTRACT FROM AUTHOR]

Alluvial rivers aggrade, incise, and adjust their sediment‐transport rates in response to changing sediment and water supply. Fluvial landforms, such as river terraces, and downstream stratigraphic archives may therefore record information about past environmental change. Using a physically based model describing sediment transport and long‐profile evolution of alluvial rivers, we explore how their responses to environmental change depend on distance downstream, forcing timescales, and whether sediment or water supply is varied. We show that amplitudes of aggradation and incision, and therefore the likelihood of terrace formation, are greater upstream and in shorter and/or wetter catchments. Aggradation and incision, and therefore terrace ages, may also lag behind environmental change. How sediment‐transport rates evolve depends strongly on whether water or sediment supply is varied. Diverse responses to environmental change could arise in natural alluvial valleys, controlled by their geometry and hydrology, with important implications for paleo‐environmental interpretations of fluvial archives. Plain Language Summary: Rivers carry sediment from upland regions, where it is produced by weathering and erosion, to low‐lying areas where it is deposited and stored. This process is sensitive to climate: for example, wetter conditions enhance rivers' capacity to transport sediment, causing rivers to cut into their beds, which in turn remobilizes sediment that is transported downstream. Changing climate may also lead to enhanced sediment production and supply to rivers, causing them to accumulate sediment in their beds. Climate cycles can therefore produce alternating periods of sediment accumulation and removal, resulting in ancient floodplains being abandoned and preserved alongside modern rivers ("terraces"), and in variations in the amounts of sediment delivered downstream. Terraces and patterns of sediment accumulation downstream could therefore provide valuable records of past climatic change. We develop a mathematical model that describes the effects of climatic change on river‐bed height and sediment‐transport rates. We show how the amount and timing of river in‐filling and down‐cutting, and the timescales over which they occur, depend on the rate of climatic change, on river length and associated drainage‐basin area, and on the amount of water it carries. These predictions will facilitate more detailed interpretations of terrace records along rivers and of the sedimentary deposits that they leave behind. Key Points: Alluvial rivers respond in diverse ways to cyclical climatic change depending on their geometry and hydrology and on the forcing frequencyTerrace formation is favored upstream and in shorter and wetter catchments and may lag appreciably behind environmental changeVariation in sediment output lags variation in sediment supply but can lead and be amplified with respect to variation in water supply [ABSTRACT FROM AUTHOR]

Human intervention makes river channels adjust their slope and bed surface grain size as they transition to a new equilibrium state in response to engineering measures. Climate change alters the river controls through hydrograph changes and sea level rise. We assess how channel response to climate change compares to channel response to human intervention over this century (2000–2100), focusing on a 300‐km reach of the Rhine River. We set up a schematized numerical model representative of the current (1990–2020), non‐graded state of the river, and subject it to scenarios for the hydrograph, sediment flux, and sea level rise. We conclude that the lower Rhine River will continue to adjust to past channelization measures in 2100 through channel bed incision. This response slows down as the river approaches its new equilibrium state. Channel response to climate change is dominated by hydrograph changes, which increasingly enhance incision, rather than sea level rise. Plain Language Summary: Humans have modified rivers to enable boat traffic, to protect people against flooding, and to provide them with freshwater and energy. When the shape of a river changes, the amount of sand and gravel (sediment) that can move along its bed also changes. In response, rivers change their slope and bed characteristics, so that they can transport as much sediment as they receive from higher up in the basin. This results in changes in bed level, which becomes higher or lower, causing problems for navigation and flood protection. Climate change makes this worse, because it changes the amount of water flowing down the river, and sea level. This further affects the amount of sediment that can move down the river, therefore causing additional bed level change. Here we study how climate change affects the lower Rhine River (Germany‐Netherlands), over the 21st century. This river has been heavily modified by humans, and its bed has been lowering over hundreds of kilometers. With a computer model, we simulate how different scenarios of climate change affect this behavior. We foresee that the ongoing bed level lowering will continue in the upcoming decades, and that it will be enhanced by climate change. Key Points: Human intervention will continue to govern channel response in the lower Rhine River by 2100, mainly through channel bed incisionClimate change leads to sea level rise and hydrograph adjustment, the latter being dominant and causing enhanced incisionChannel response to human intervention slows down as the river approaches its equilibrium state, but response to climate change accelerates [ABSTRACT FROM AUTHOR]

The evolution of the East Asian winter monsoon (EAWM) during the Holocene remains controversial because of the lack of reliable proxies. In this study, a link between cross‐front transport and the EAWM was found in the North Yellow Sea, and the EAWM intensity could be imprinted in the leaked sediment, which permits reliable reconstruction of the EAWM on well‐preserved offshore deposition. By comparison with instrumental data, the wind speed of the EAWM since 4.4 ka was quantitatively reconstructed for the first time at high resolution (∼5 yr). The results show that the EAWM gradually weakened in the mid‐to‐late Holocene, which was likely controlled by solar insolation, and that there has been a negative relationship between the EAWM and temperature on the centennial scale since ∼2.0 ka; this relationship was reversed by increasing CO2 emissions during the Current Warm Period. Plain Language Summary: The East Asian monsoon is characterized by a distinct seasonal reversal of monsoon flow driven by temperature differences between the Pacific Ocean and the East Asian continent. It influences more than 2 billion people around East Asia by regulating the risk of drought or flooding. However, the evolution of the East Asian winter monsoon (EAWM) in the mid‐to‐late Holocene remains elusive, limiting our understanding of its driving force and projections under climate change. This study analyzed sediment transport dynamics under varying winter monsoons in the North Yellow Sea. It was found that coastal sediments could be transported offshore, and their pathways differed under different strengths of the winter monsoon. Based on the sedimentary records of offshore muddy deposition, the EAWM proxy was extracted, and the wind speed of the EAWM from 4.4 ka was quantitatively reconstructed. A gradual weakening trend during 4.4–0.7 ka and a dramatic strengthening after 0.2 ka were found in the EAWM; the EAWM was negatively related to the temperature on the centennial scale since ∼2.0 ka, but this relationship was reversed by an increase in CO2 emissions since ∼1800 CE, indicating a shift in the controlling mechanism. Key Points: A link between cross‐front transport and the East Asian winter monsoon (EAWM) was found in the shelf sea, and the leaked sediment was used to reconstruct the EAWMThe wind speed of the EAWM since 4.4 ka was quantitatively reconstructed at high resolution (∼5 yr) for the first timeCorrelation between the EAWM and the temperature on the centennial scale since ∼2.0 ka was reversed by the increasing CO2 at the Current Warm Period [ABSTRACT FROM AUTHOR]

Changes in river channel morphological parameters are influenced by anthropogenic factors, such as climatic changes, river catchment management changes, and hydrotechnical development of rivers. To assess the intensity of individual pressures and the resulting changes in abiotic and biotic factors in the riverbed, water quality monitoring is conducted, including the assessment of the hydromorphological status. The assessment can be based on the River Habitat Survey (RHS) which is a synthetic method that includes the evaluation of habitat character and river quality based on their morphological structure. The input data, which characterise any river include physical features of hydrotechnical structures, bed granulation, occurrence of bedforms, visible morphodynamic phenomena, and a sediment transport pattern. The RHS method allows to determine two quantitative indices used to evaluate the hydromorphological status: Habitat Modification Score (HMS), which determines the extent of transformation in the morphology of a watercourse, and Habitat Quality Assessment (HQA), which is based on the presence and diversity of natural elements in a watercourse and river valley. The proposed method can be divided into three stages. The first assesses the river section hydromorphological indices, describing the degree of technical modification (HMS) and the ecological quality of the reach (HQA), using the RHS method. The second stage describes morphological changes resulting from the technical regulation and estimates indices for the regulated reach. Finally, we compare HQA and HMS indices before and after the regulation. This comparison is described by numerical indicators and related to reference values. [ABSTRACT FROM AUTHOR]

Purpose: Soil erosion and sediment transport are often induced by a few extreme precipitation events. Currently, there is limited information on the effects of changes in precipitation extremes on river sediment load over a long time period at the basin scale. The objectives of this study were to quantify the effects of variations in precipitation extremes on sediment load in the Second Songhua River Basin (SSRB), northeast China. Materials and methods: Daily precipitation data from 10 meteorological stations within the SSRB and sediment load data during 1960–2014 from the basin outlet hydrological station were collected. Six extreme precipitation indices, such as erosive precipitation (ERPTOT), wet-day precipitation (PRCPTOT), very wet day precipitation (R95pTOT), flood season precipitation (FSPTOT), maximum 1-day precipitation (RX1day) and heavy precipitation (HP), were used to detect the precipitation extremes. The Mann–Kendall non-parametric trend analysis was used to analyze the dynamic changes in precipitation extremes and sediment load. The double cumulative curve method was used to assess the effects of changes in precipitation extremes on sediment load. Results and discussion: The results indicated that six extreme precipitation indices showed periodic variations from 1960 to 2014, while they did not show any significant change trend in the SSRB (p > 0.05); however, the sediment load showed an extremely significant decreasing trend (p < 0.01) over the past 55 years. Sediment load significantly correlated with six precipitation extremes indices (p < 0.05). Compared with the baseline period (1960–1977), the sediment load was reduced by 1.12 × 106 ton per year (1977–2014). The contribution of precipitation extremes to the sediment load ranged from -22.83% to 6.97%. The corresponding contribution of the non-precipitation factor to sediment load was from 93.03% to 122.83%. Conclusions: The change in precipitation extremes was not the main reason for the sediment load reduction. Sediment load reduction in the SSRB was due to the interactions between multiple factors. Non-precipitation factors, such as reservoir construction, were the main reasons for the sediment load reduction. These findings are useful to understand the variation of river sediment load and to adopt countermeasures to relieve potential risk of precipitation extremes. [ABSTRACT FROM AUTHOR]

Human activities and climate change are recognized as two of the most important drivers of hydrologic variability and have attracted the interest of researchers over the past decade. Changes in land use, dam construction, agricultural development, and global warming are forces that directly or indirectly impact the global and local hydrologic regime. This study examines the effects of these drivers on streamflow and sediment transport in the Gorganroud watershed, located in the north of Iran. In addition, the most sensitive land use patterns are detected using statistical approaches and a hydrologic model. The current study's principal argument is based on the variability of land use patterns during the modeling procedure (2007–2019). The Soil and Water Assessment Tool (SWAT) model is used to consider the land use dynamics during the simulation period based on the hydrological regime of the reference period. The Simple Differential Method (SDM) and Climate Elasticity Method (CEM) are utilized to estimate the contribution rates of land use and climate change in streamflow and sediment transport changes. The results indicate that changes in land use have contributed more than 60% to streamflow and sediment regime changes in all subbasins. A sensitivity analysis of land uses and the spatial distribution of the Human Contribution Rate (HCR) over the study area reveal that an increase in orchard land use (8.7% during the computational period) is primarily responsible for these significant changes. [ABSTRACT FROM AUTHOR]

Bed stress patterns control erosion and deposition in tidal rivers and thereby govern changes in geomorphology. Management of river discharge and shipping channel geometry perturbs rivers from their natural state, leading to hotspots of sand deposition and erosion. Here, we investigate the along-channel variability in bed stress for a tidal river of constant depth with semidiurnal tides and convergent geometry using a Fourier decomposition of the quadratic bed stress and analytical approximations of tidal and river velocity. Under some river discharge and tidal conditions, bed stress profiles exhibit a local bed stress minimum, xmin, within a region marked by strong gradients in cross-sectionally averaged velocity. These gradients can lead to convergent sediment fluxes and shoaling near xmin. Factors decreasing river velocity (flow management, channel deepening, and weak channel convergence) move xmin and depositional areas upstream. Analytical estimates of xmin were validated using fifty-two two-dimensional Adaptive Hydraulics (AdH) numerical model simulations and agree well with the sediment transport behavior of three prototype systems (Columbia River, Hudson River, and Delaware Estuary). Climate changes in seasonal flow cycles and mean river discharge, and the reservoir management response to these changes, may significantly alter the dynamics of xmin, affecting ecosystem dynamics and the stability of wetlands and coastal beaches as sea level rises. The analytical formulation of xmin developed herein will make it easier to understand how climate and human-induced changes to a river can impact long-term erosion/accretion patterns and can help guide future investments for managing sediment. [ABSTRACT FROM AUTHOR]

Riverbank migration has historically been seen as a risk to infrastructure that can be combated through channelization, bank stabilization, and sediment trapping. The physical processes involved with riverbank erosion and deposition are well defined, yet the solutions to equations that describe these processes are computationally and data intensive over large domains. While current understanding of large‐scale river channel mobility largely comes from reach‐ and watershed‐scale observations, we need global observations of riverbank erosion and accretion to broaden our understanding of sediment processes within and across river basins. In this work, we create the first global data set of riverbank erosion for >370,000 km of large rivers using up to 20 years of water classifications from Landsat imagery. We estimate uncertainty by propagating water classification errors through our methods. Globally, we find riverbank erosion for rivers wider than 150 m to have an approximately log‐normal distribution with a median value of 1.52 m/yr. Comparing our data set to 25 similar estimates of riverbank migration, we found a normalized mean absolute error of 42% and a bias of 5.8%. We show that river width is the best first‐order predictor of riverbank erosion, in agreement with existing literature. We also show that the relationship between width and bank erosion is substantially different among a sample of global river basins and suggest that this is due to second‐order influences of geology, hydrology, and human influence. These data will help improve models of sediment transport, support models of bank erosion, and improve our understanding of human modification of rivers. Plain Language Summary: Riverbank erosion presents a serious risk to people and infrastructure. These risks are becoming increasingly difficult to predict because of direct modification of the rivers by damming and bank stabilization, as well as indirect modification by climate change and land use change. Geomorphologists have developed scaling relationships based on watershed characteristics; however, these relationships are very coarse and limited by the available data. This research uses 20 years of satellite imagery to develop the first global data set of riverbank erosion, which both confirm existing knowledge and opens new avenues of research. Key Points: We developed the first global data set of riverbank erosion and accretion for rivers wider than 150 mWe confirm that regional first‐order relationships between river width and riverbank erosion apply globallyWe show large interbasin differences in riverbank erosion that arise from the unique geography of each river basin [ABSTRACT FROM AUTHOR]

Artificial reservoirs are crucial infrastructures, since they allow for the management of the water resource they store and for their role in the hydroelectric production. Water is modulated and stored inside artificial basins built upstream of the dams for hydroelectric, industrial, drinking, irrigation, and flood mitigation purposes. However, as time passes, the deposition of solid material, transported by rivers flowing into the reservoir, reduces its storage capacity. In this work, a novel physicallybased erosion and sediment transport model developed by Politecnico di Milano (SMART-SED) is used to estimate dam filling in different Italian geological contexts. The present model differs from others in the literature since it can automatically detect drainage zones and it works at a basin scale, requiring few input parameters that can be easily downloaded from global or government databases. Moreover, it is based on robust and unconditionally stable numerical techniques, and it guarantees the mass conservation. The proposed model was applied to four watersheds, two in the Southern Alps and two in the Southern Apennines, with catchment areas ranging from 5 to 48 km². After the model calibration on the local geological context, a validation of the obtained results was accomplished considering different time intervals and the available sediment filling data. It was observed that the SMART-SED model, initially developed for the evaluation of fluvial hazard and of sediment transport in mountainous areas, was also suitable for the estimation of dam filling. Results indeed show a precise approximation of the order of magnitude of the cumulative sediment volume produced inside the catchments and transported to the water basins. In the framework of a complex problem affecting the production of "clean" energy in a changing world, SMART-SED could become a useful tool also for dam management. [ABSTRACT FROM AUTHOR]

Wave-dominated sandy beaches are highly valued by societies and are amongst the world's most energetic and dynamic environments. On wave-dominated beaches with unlimited sand supply and limited influence of tide and geology, beach change has long been conceptualised in the morphodynamic framework of Wright and Short (1984). Such framework describes the occurrence of beach types based on wave conditions and sediment characteristics across the complete reflective-dissipative spectrum. Building on theoretical work, field/laboratory measurements and monitoring programmes, the physical mechanisms underpinning this morphodynamic framework have been progressively unravelled. Cross-shore morphological changes are primarily controlled by equilibrium and beach memory principles with below (above) average wave conditions driving down-state (up-state) transitions associated with onshore (offshore) sediment transport. Such cross-shore behaviour mostly reflects the imbalance between the onshoredirected sediment transport driven by wave nonlinearities and the offshore-directed sediment transport driven by the undertow. Self-organised morphological instabilities resulting from different positive feedback mechanisms are primarily responsible for alongshore morphological variability and the generation of rhythmic morphological features, such as crescentic bars, rip channels and beach cusps. Critically, wave climate and changes in wave regimes are key in driving the coupled cross-shore and longshore behaviour that ultimately explains modal beach state and frequency-response characteristics of beach morphological time series. [ABSTRACT FROM AUTHOR]

Natural and anthropogenic activities have accelerated the coastal erosion in Sri Lanka by threatening the economic developments and livelihoods in coastal zones. However, there is a limited number of studies on coastal erosion in Sri Lanka due to the lack of observed wave climate data around the island. This study identified the impact of wave climate changes on the littoral drift of seven selected locations in Sri Lanka. The reanalyzed wave climate data were used to estimate sediment transport rate in seven locations using empirical methods. The chronological volumetric changes of Kalutara and Kalpitiya beach volume were estimated, as those beaches experienced severe morphological changes during the above period. The relationship among the capacity of coastal sediment transportation of littoral drift, actual sediment accretion (and erosion), and shoreline management activities was critically discussed by collecting data from diverse sources to its fullest extent. The wave climate becomes rough on the western and southern coasts during the southwest monsoon and the eastern coast during the northeast monsoon. The average wave direction periodically changes on the southwest coast, and thus, the littoral drift occurs southwards at the Kalutara coast. The Kalpitiya areas were the main sediment accretion areas, but the Kalplitiya peninsula is slowly eroding with the recently intensified wave climate. Coastal erosion is an integrated effect of shoreline management, wave climate change, and reduction of river sediment supply. Therefore, coastal erosion should be studied with accurate numerical and physical model studies for the betterment of erosion management. [ABSTRACT FROM AUTHOR]

Purpose: The study tracks spatial and temporal distribution of sediment particles from their source to the deposition area in a dammed reservoir. This is particularly important due to the predicted future climate changes, which will increase the severity of problems with sediment transport, especially in catchments prone to erosion. Methods: Analyses were performed with a monthly step for two mineral and one mineral/organic sediment fractions delivered from the Carpathian Mts. catchment (Raba River) to the drinking water reservoir (Dobczyce) by combining SWAT (Soil and Water Assessment Tool), and AdH/PTM (Adaptive Hydraulics Model/Particle Tracking Model) modules on the digital platform—Macromodel DNS (Discharge Nutrient Sea). To take into account future changes in this catchment, a variant scenario analysis including RCP (representative concentration pathways) 4.5 and 8.5, and land use change forecasts, was performed. Results: The differences between the two analyzed hydrological units (catchment and reservoir) have been highlighted and showed a large variability of the sediment load between months. The predicted climate changes will cause a significant increase of mineral fraction loads (silt and clay) during months with high flows. Due to the location and natural arrangement of the reservoir, silt particles will mainly affect faster loss of the first two reservoir zones capacities. Conclusions: The increased mobility of finer particles (clay) in the reservoir may be more problematic in the future, mainly due to their binding pollutant properties, and the possible negative impact on drinking water abstraction from the last reservoir zone. Moreover, the study shows that the monthly approach to forecasting the impact of climate change on sediment loads in the reservoir is recommended, instead of a seasonal one. [ABSTRACT FROM AUTHOR]

Soil erosion rates are high in many parts of Southern Africa, and are likely to rise because of climate change. Suspended sediment loads (SSL) and yields (SSY) are used to measure and benchmark soil erosion and/or sediment transport rates and determine trajectories of change. Some modelled SSY are available for Southern African catchments, but there is a dearth of contemporary observed data. Northern hemisphere approaches to suspended sediment measurement and the calculation of loads and yields are often unsuited to Southern Africa: locally appropriate methods are required. The manual, flood‐focused suspended sediment sampling programme that we implemented in the eroded and data‐scarce Tsitsa River catchment (Eastern Cape, South Africa) monitored four sub‐catchments from December 2015 to June 2019 at a sub‐daily timestep. We used a discharge‐weighted interpolation SSL estimator, investigating the effects of catchment area, hydrological regime, and sampling strategy on SSL, SSY, and variability, comparing our estimates with modelled results. Discharge increased with catchment area whilst flashiness (expressed by the Richards‐Baker Flashiness Index) mainly decreased, and was similar to that of North American catchments. The sampling frequency required to maintain precision was inversely related to catchment area. Mean annual SSL ranged from 18 121 t year−1 in the 204 km2 Gqukunqa River catchment to 984 267 t year−1 in the 1452 km2 Inxu River catchment. Mean annual SSY ranged from 61 t km2 year−1 in the 432 km2 Pot River catchment to 678 t km2 year−1 in the Inxu River catchment. Data stratification to limit sampling to wet‐season flows did not significantly impact SSL estimates, but year‐round sampling is required to maintain the citizen‐technician sampling network through regular income. Modelled SSY estimates were higher than our measured estimates. Our approach to suspended sediment sampling, load and yield estimation is robust, sustainable, precise, and can be adapted for similar, remote catchments. [ABSTRACT FROM AUTHOR]