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This study discusses the coastal sediment budget for the Ishikawa coast using 12 years of observational datasets; it involves an understanding the local and regional sediment dynamics, the intensity of the transport processes in the region, and sediment supply from a local river. Although alongshore sediment transport and sediment budgets have been analyzed in previous studies, only a few conducted cross-shore sediment transport evaluations. The concentration of suspended sediments will be determined in this study, taking into account the influence of waves that are associated with the coastal current. The cross-shore sediment transport using sediment budget analysis indicated that the net alongshore sediment transport directions in the surf and offshore zones are opposite on the Ishikawa coast. The increase in the sediment budget of the surf zone can be attributed to the river sediment supply and longshore sediment transport inflow. Because of the significant outflow components of longshore and cross-shore sediment transports, the offshore zone budget showed a decreasing trend. A detailed sensitivity study was performed by varying the input parameters, in order to determine the possible ranges of net transport rates and sediment transport to the adjacent coasts. The results demonstrated the possibility of a clockwise residual sediment circulation. Our method can be used to analyze the alongshore sediment transport for other coasts and supplement future studies on coastal sedimentology and sediment budgets.

Parnell, K.E. and Soomere, T., 2024. Geomorphic metrics for implementing a ‘rights of nature’ approach in coastal management. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 38-42. Charlotte (North Carolina), ISSN 0749-0208. Although the approach is decades old, Integrated Coastal Zone Management (ICZM) set within a sustainability framework, has been largely unsuccessful beyond small-scale ‘feel-good’ projects. A Rights of Nature / earth jurisprudence approach to environmental management is being tested, with some jurisdictions embracing it in legislation and policy, and others (such as the European Union) taking a few tentative steps, despite the approach frequently being regarded as extreme. While the concept is broadly understood, the actual rights that must be protected specifically for the coastal environment need to be defined, and they need to be at least partially quantifiable. Eleven rights are proposed. These are a right to a) natural hydrodynamic drivers (waves, tides etc.); b) transport sediment and maintain a balanced sediment budget; c) morphological integrity and natural geodiversity; d) morphologically adjust irrespective of property rights; e) evolve; f) operate at a natural (sediment compartment) scale, spanning human borders; g) be healthy, maximizing resilience; h) be recognized as having inherent worth, regardless of perceived aesthetic, economic or strategic value; i) the integrity of supporting systems and processes; j) be free of structures that impede normal functioning; and k) be restored morphologically and functionally from the impacts of human actions. Many of these rights can be conceptualized and tested in the context of an appropriately scaled coastal sediment budget, and an example is given from the Baltic Sea.

Damming of wild rivers has trapped vast quantities of sediment that would otherwise nourish deltas, causing severe sediment deficits and accelerating delta erosion worldwide. The Yellow River Delta (YRD), once prograding seaward at ∼10 km2/yr, began retreating at −5.6 km2/yr following completion of the Xiaolangdi Reservoir. Implementation of the Water and Sediment Regulation Scheme (WSRS)—a reservoir flushing program—fundamentally reversed this trend. By mobilizing trapped sediment and enhancing downstream channel scouring, the WSRS increased sediment delivery to the sea from 17.6 Mt/yr before its initiation to 178.5 Mt/yr during operation years. This renewed sediment flux restored delta growth, producing subaerial expansion of 6–7 km2/yr and significant subaqueous deposition near the estuary. These results demonstrate that the YRD has entered a new phase of evolution under active human management and highlight that sediment trapped behind dams can become a potentially important source for restoring sediment‐starved deltas worldwide.

Regular release of sediment from reservoir has been increasingly adopted as a strategy for sustainable management. Here, we use a process‐based morphodynamic model to simulate the estuarine sediment dynamics impacted by turbidity current venting implemented by the Shihmen Reservoir during three typhoon events in 2008. Upon validation with the post‐event bathymetries, the model hindcasts reveal that mud releasing can be effective in mitigating reservoir siltation, yet may be a suboptimal strategy for alleviating coastal sediment deficit. A vast majority of the released muds were delivered through the estuary and exported to offshore by flood advection, wave dispersion, and tidal flushing. The flood‐driven sands, sourced mainly from downstream tributaries, were instead the major contributor to coastal sediment budget. However, mud mantling (covering and immobilizing sand deposits by the reservoir‐released muds) reduced sand availability and thus sand delivery to the coast. For the present case, 25% of the released muds were deposited along the way, presence of these mud covers reduced sand delivery by 15%, compared to a hypothetical scenario of clear‐water flood releases. The relative sand transport deficit is found to increase linearly with the degree of bed mud saturation, 1–D/R, with D/R the ratio of single‐event mud deposit to release. Given broad relevance to global reservoirs encountering the problems of siltation and coastal sediment deficit, our findings highlight that sustainable management needs to look beyond just a bulk amount of sediment, but it is critical to consider how different sediment fractions are interacting and impacted by human activities. Key Points Increasingly adopted mud release strategy is effective to mitigate reservoir siltation yet suboptimal to alleviate coastal sediment deficit Flood‐driven tributary‐sourced sands dominate supply to coastal sediment budget yet sand delivery is reduced by mantling of released muds Sand delivery deficit (relative to sand delivery of clear‐water flood release scenario) increases linearly with degree of bed mud saturation

PurposeThe sediment dynamics of (peri-)glacial catchments can be highly variable and complex. Understanding these dynamics and their underlying causes is not only of interest from a scientific perspective but also required to address the practical problems with which they are often associated. In order to better understand the sediment dynamics of glaciated mountainous catchments, suspended sediment fluxes in the 9.1 km2 Djankuat catchment (North Caucasus, Russia) were monitored intensively during the 2017 ablation season.Materials and methodsThe intra-event suspended sediment dynamics were studied using a newly proposed simple hysteresis index (SHI), quantifying to what extent evolutions in sediment concentration are characterized by a clockwise or anticlockwise hysteresis loop.Results and discussionThe resulting catchment suspended sediment yield was 1033 t km−2 year−1, with the glacier itself contributing 72% of the suspended sediment load. However, during rainfall events, also hillslope erosion in the proglacial area became a very significant sediment source. Clockwise hysteresis loops occurred in 61.8% of the events, while anticlockwise in 11.8%. On the other hand, only 47.8% of the total suspended sediment flux was transported during clockwise events. Our observations clearly indicate that events showing a stronger clockwise pattern (i.e., a higher SHI) are associated with a larger sediment input from the proglacial area.ConclusionsOverall, our results provide data and insights on sediment dynamics in an understudied environment. They illustrate that the type and characteristics of sediment concentration hysteresis loops are to some extent linked to the dominant sediment sources during the event. As such, the proposed methodology and SHI may also help with a better understanding of sediment dynamics in other environments.

The degradation of soil through erosion poses a major environmental concern on a global scale, adversely affecting the chemical, biological, and physical properties of both soil and water. Precisely identifying the main sediment sources within a watershed is vital for developing targeted management strategies aimed at reducing erosion and improving water quality. Sediment sourcing is a commonly employed approach to achieve this goal. Some sediment sourcing methods not only determine the contributions of different sources but also provide estimates of average erosion/sedimentation intensity and sediment budget components. Therefore, the present study was conducted with the aim to compare the average soil erosion intensity and sediment yield in the past 100–120, 60–70, and 15 years within the control sub-watershed of the Khamsan representative-paired watershed. Furthermore, the contribution of various land uses to sediment yield, such as orchards, irrigated agriculture, rangeland, and rainfed agriculture were compared using geochemical fingerprinting characteristics obtained in 2021 with the corresponding results derived from the 137 Cs method for the last 60–70-year period. In order to achieve the research objectives, a total of 106 soil samples were systematically collected with appropriate distribution in different land uses for sediment source fingerprinting using radionuclides and other indicators. The findings indicated that during the two recent periods, spanning 100–120 years and 60–70 years, the average gross erosion was estimated at 2.92 and 5.25 t ha −1 y −1 , respectively, and the average net erosion was estimated at 2.85 and 5.05 t ha −1 y −1 , respectively. Furthermore, the contributions of rainfed agriculture and rangeland to sediment yield in 2021 were 72.26% and 7.96%, respectively, and using the 137 Cs method for the 60–70-year period, they were 85.49% and 8.93%, respectively. The study’s findings revealed also a decline in sediment yield over the past 60–70 years, compared to the measurements obtained during the last 15 years. This decrease can be primarily attributed to factors that include the abandonment of rainfed agricultural lands, a decrease in rainfall, and a reduction in sediment transport caused by tillage in waterways draining to the sub-watershed outlet.

Coral reef islands are amongst the most vulnerable environments to sea‐level rise (SLR). Recent physical and numerical modeling studies have demonstrated that overwash processes may enable reef islands to keep up with SLR through island accretion. Sediment supply to these islands from the surrounding reef system is critical in understanding their morphodynamic adjustments, but is poorly constrained due to insufficient knowledge about sediment delivery rates. This paper provides the first estimation of sediment delivery rates to coral reef islands. Analysis of topographic and geochronological data from 28 coral reef islands indicates an average rate of sediment delivery of c. 0.1 m3 m−1 yr−1, but with substantial inter‐island variability. Comparison with carbonate sediment production rates from census‐based studies suggests that this represents one quarter of the amount of sediment produced on the reef platform. Results of this study are useful in future modeling studies for predicting morphodynamic adjustments of coral reef islands to SLR. Plain Language Summary Low‐lying coral reef islands are under threat of sea‐level rise (SLR). However, when these islands are flooded, ocean waves can bring in sediment that can increase the island elevation. This would enable coral reef islands to better withstand flooding in the future. Knowing how much sediment is brought in will help in our understanding of future changes to these islands due to SLR. In this paper, we use data from 28 Indo‐Pacific coral reef islands to compute sediment supply to the islands. We find that on average 0.1 m3 of sediment (roughly 100 kg) is delivered each year for every meter of island shoreline. We further suggest that this implies that only one quarter of the sediments produced by the coral reef system is delivered to the island shoreline. Most of the sediment produced remains on the reef flat or is exported to the ocean or the lagoon. Our results will help future studies to predict more accurately how coral reef islands will adjust to SLR. Key Points We provide the first estimates of carbonate sediment delivery rates to 28 coral reef islands using all data available from the literature Sediment delivery to the reef islands occurs at a rate of c. 0.1 m3 m−1 yr−1, but with substantial inter‐island variability Where island building has been continuous through island history, long‐term delivery rates provide valuable estimates for contemporary rates

Information on sediment concentration in rivers is important for the design and management of reservoirs. In this paper, river sediment flux and siltation rate of a rift valley lake basin (Lake Ziway, Ethiopia) was modeled using suspended sediment concentration (SSC) samples from four rivers and lake outlet stations. Both linear and non-linear least squares log–log regression methods were used to develop the model. The best-fit model was tested and evaluated qualitatively by time-series plots, quantitatively by using watershed model evaluation statistics, and validated by calculating the prediction error. Sediment yield (SY) of ungauged rivers were assessed by developing and using a model that includes catchment area, slope, and rainfall, whereas bedload was estimated. As a result, the gross annual SY transported into the lake was 2.081 Mton/year. Annually, 0.178 Mton/year of sediment is deposited in floodplains with a sediment trapping rate of 20.6%, and 41,340 ton/year of sediment leaves the lake through the Bulbula River. The annual sediment deposition in the lake is 2.039 Mton/year with a mean sediment trapping efficiency of 98%. Based on the established sediment budget with average rainfall, the lake will lose its volume by 0.106% annually and the lifetime of Lake Ziway will be 947 years. The results show that the approach used can be replicated at other similar ungauged watersheds. As one of the most important sources of water for irrigation in the country, the results can be used for planning and implementing a lake basin management program targeting upstream soil erosion control.

Reduced riverine sediment supply and sea-level rise (SLR) threaten land building and ecosystem in deltas. However, the sediment-morphodynamic processes in a channel-shoal complex are not well understood. Here, based on bathymetry and the Delft3D model, geomorphic changes and suspended sediment budgets in the South Passage, Nanhui and Jiuduansha Shoal in the mega-Changjiang Delta were examined. Results reveal that with riverine suspended sediment concentration (SSC) decreased by 75%, the net sediment deposition rate was reduced from 4.20 cm/yr in 1979-1990 to 3.21 cm/yr in 1990-2003, and further declined to 2.21 cm/yr in 2003-2013 and 0.40 cm/yr in 2013-2020. Severe erosion occurred along the upper South Passage and extended toward the mouth bar. Strong accretions accumulated in the Nanhui and Jiuduansha Shoal. After river SSC declined from 0.53 kg/m 3 to 0.35 kg/m 3 , 0.16 kg/m 3 , and 0.12 kg/m 3 , net suspended sediment deposition was lowered by 3.13%, 7.35% and 8.67%, respectively. Moreover, SLR of 5 cm, 15 cm, 25 cm, and 50 cm resulted in a further 1.11%, 4.18%, 4.16%, and 14.79% reduction in sediment trapping efficiency. Our findings highlight the strong likelihood that reduced river sediment input, SLRs and intensified anthropogenic effects will exacerbate sediment deficit and erosion in mega fluvial-tidal deltas.

The potential response of shoreface depositional environments to sea level rise over the present century and beyond remains poorly understood. The shoreface is shaped by wave action across a sedimentary seabed and may aggrade or deflate depending on the balance between time-averaged wave energy and the availability and character of sediment, within the context of the inherited geological control. For embayed and accommodation-dominated coastal settings, where shoreline change is particularly sensitive to cross-shore sediment transport, whether the shoreface is a source or sink for coastal sediment during rising sea level may be a crucial determinant of future shoreline change. While simple equilibrium-based models (e.g. the Bruun Rule) are widely used in coastal risk planning practice to predict shoreline change due to sea level rise, the relevance of fundamental model assumptions to the shoreface depositional setting is often overlooked due to limited knowledge about the geomorphology of the nearshore seabed. We present high-resolution mapping of the shoreface-inner shelf in southeastern Australia from airborne lidar and vessel-based multibeam echosounder surveys, which reveals a more complex seabed than was previously known. The mapping data are used to interpret the extent, depositional character and morphodynamic state of the shoreface, by comparing the observed geomorphology to theoretical predictions from wave-driven sediment transport theory. The benefits of high-resolution seabed mapping for improving shoreline change predictions in practice are explored by comparing idealised shoreline change modelling based on our understanding of shoreface geomorphology and morphodynamics before and after the mapping exercise.