Natural Flood Research Articles

Can we adapt fairly? Systematic review of health equity implications of climate change in coastal communities in the UK

Abstract As climate change becomes more apparent, it is important to evaluate the equity implications of adaptation interventions and policy measures. Many coastal populations experience high levels of social deprivation, which can be compounded by environmental factors. Coastal hazards, such as erosion and flooding can cause short and long term impacts on physical and mental health. To systematically review the published evidence on the differential impacts of coastal change on health inequalities and review the implications of adaptation responses for health inequality. We systemically reviewed the evidence for the UK only on a) inequalities in coastal flood impact or risk, and b) effectiveness and equity implications of current measures to manage the climate risks to an acceptable level of impact. Interventions included: plans and guidance, insurance, and infrastructure, including natural flood management. We found 8 papers quantifying differentials in current and future impacts of coastal flood risk and 6 papers assessing equity implications of adaptation measures. Coastal flood risk is unevenly distributed. Those owning their own home were more likely to experience flood impacts including increased stress and displacement. There is good evidence that policies for household insurance and property level protection measures have the potential to increase inequalities; other measures (community engagement; planning; defences) may reduce health inequalities, depending on implementation and local context. Adaptation to coastal change requires a range of approaches in the short and longer term, which potentially exacerbate current inequalities. Adaptation responses that rely on individual behaviour change, such as relocation, purchasing insurance, or retrofitting dwellings, may exacerbate inequalities within coastal communities. Climate change challenges organisations to deliver national and local policy responses ensuring that adaptation is effective and equitable.

Understanding bi-modal seas, shingle beach response and flood risk at Hayling island, UK

Beach management through nourishment and annual recycling has been applied for over 37 years to manage flood and coastal erosion risk to 1700 properties at Eastoke, Hayling Island, UK. This form of natural flood risk management has proved successful in avoiding the annual flooding that blighted this area previously. However there have been unexpected storm events which have caused beach erosion and localised flooding. Using long-term nearshore wave datasets and state-of-the-art statistical methods, new multivariate extreme wave conditions were derived. The conditions were applied to simulate beach profile response, estimated bimodal overtopping rates and resulting flood inundation, then validated against recent storm events. The Eastoke beach was found to meet its original design criteria of a 0.5% AEP standard of protection for unimodal wave conditions. However, it experiences greater roll back erosion, wave overwash and therefore flood inundation under certain bimodal wave conditions, causing uncertainty around the future standard of protection.It remains unclear if the unexpected beach response at Eastoke resulted from increased storminess due to climate change, additional loading by mixed sea/swell events, increasing bimodal events, or the assumptions within the original bivariate analysis, leading to incorrect AEP attribution.Communicating these issues to practitioners and a non-specialist audience is challenging as we tend to oversimplify, despite every beach and storm being unique. Better understanding of mixed beaches both in situ and through parametric and numerical models would reduce uncertainty, to ensure communities are resilient to climate change.

Physically-based modelling of UK river flows under climate change

This study presents the model setup and results from the first calibrated, physically-based, spatially-distributed hydrological modelling of combined land cover and climate change impacts on a large sample of UK river catchments. The SHETRAN hydrological model was automatically calibrated for 698 UK catchments then driven by the 12 regional climate model projections from UKCP18, combined with urban development and natural flood management scenarios. The automatic calibration of SHETRAN produces a median Nash-Sutcliffe efficiency value of 0.82 with 581 catchments having a value greater than 0.7. 24 summary metrics were calculated to capture changes to important aspects of the flow regime. The UKCP18 realisations in SHETRAN indicate that a warming climate will cause river flows, on average, to decrease. These decreases are simulated to be greatest in the south and east of the UK, with droughts becoming longer and more severe. While high flows also decrease on average, an increased number of extremes are exhibited, implying a greater number of extreme flood events in the future, particularly in the north and west of the UK. In the urban development scenarios, for flood events there is an increase in flow with the increased urbanization, with the 1 in 3-year peak flow event showing the greatest increase. The natural flood management scenarios consider the effect of increasing woodland and adding surface water storage ponds. The inclusion of these features produces a complex response but overall, the modelling shows a reduction in low, median, and high flows, although the more extreme the flow event the smaller the percentage change in flow. Simulated timeseries and summary metric datasets are freely available on the CEDA archive.

Disentangling the Effects of Multiple Impacts of Natural Flooding on a Riverine Floodplain Lake by Applying the Phytoplankton Functional Approach

Riverine floodplains are ecologically remarkable systems that have historically faced strong anthropogenic pressures. The aim of this study was to examine whether the phytoplankton functional approach by Reynolds is a useful tool for disentangling anthropogenic pressure from the impact of natural flooding on a riverine floodplain lake. Lake Sakadaš, part of the large conserved river–floodplain system along the Danube River (Kopački Rit, Croatia), was used as a case study. Historical data on phytoplankton dynamics from the 1970s, when the lake was exposed to direct inflows of agricultural wastewater, were compared with current data from a time when the lake was a strongly protected area. Analysis of the phytoplankton community, based on functional groups and their beta diversities, revealed clear variation between the observed periods. The heavy bloom of species from only one functional group with extremely high biomass indicated a highly impacted environment in the past. Recent data suggest that, with the cessation of direct pollution, near-natural hydrological conditions with flooding as a fundamental environmental driving factor, support algal assemblages characteristic of a naturally eutrophic lake. Assessing multiple pressures on floodplain lakes and disentangling their specific impacts on ecological statuses are crucial for defining the protection and sustainable management of these particularly sensitive and endangered freshwater systems.

Evaluating Flood Damage to Paddy Rice Fields Using PlanetScope and Sentinel-1 Data in North-Western Nigeria: Towards Potential Climate Adaptation Strategies

Floods are significant global disasters, but their impact in developing countries is greater due to the lower shock tolerance, many subsistence farmers, land fragmentation, poor adaptation strategies, and low technical capacity, which worsen food security and livelihoods. Therefore, accurate and timely monitoring of flooded crop areas is crucial for both disaster impact assessments and adaptation strategies. However, most existing methods for monitoring flooded crops using remote sensing focus solely on estimating the flood damage, neglecting the need for adaptation decisions. To address these issues, we have developed an approach to mapping flooded rice fields using Earth observation and machine learning. This approach integrates high-resolution multispectral satellite images with Sentinel-1 data. We have demonstrated the reliability and applicability of this approach by using a manually labelled dataset related to a devastating flood event in north-western Nigeria. Additionally, we have developed a land suitability model to evaluate potential areas for paddy rice cultivation. Our crop extent and land use/land cover classifications achieved an overall accuracy of between 93% and 95%, while our flood mapping achieved an overall accuracy of 99%. Our findings indicate that the flood event caused damage to almost 60% of the paddy rice fields. Based on the land suitability assessment, our results indicate that more land is suitable for cultivation during natural floods than is currently being used. We propose several recommendations as adaptation measures for stakeholders to improve livelihoods and mitigate flood disasters. This study highlights the importance of integrating multispectral and synthetic aperture radar (SAR) data for flood crop mapping using machine learning. Decision-makers will benefit from the flood crop mapping framework developed in this study in a number of spatial planning applications.

Maintenance of High Phytoplankton Diversity in the Danubian Floodplain Lake over the Past Half-Century.

Riverine floodplains are recognized as centers of biodiversity, but due to intense anthropogenic pressures, many active floodplains have disappeared during the last century. This research focuses on the long-term changes in phytoplankton diversity in the floodplain lake situated in the Kopački Rit (Croatia), one of the largest conserved floodplains in the Middle Danube. The recent dataset from 2003 to 2016 and historical data from the 1970s and 1980s indicate high phytoplankton diversity, summarising 680 taxa for nearly half a century. The variability of species richness is driven by specific in-lake variables, particularly water temperature, water depth, total nitrogen, pH, and transparency, determined by a redundancy analysis of the current data. The high phytoplankton diversity levels are sustained regardless of intense pressures on the lake environment, including exposure to strong anthropogenic pollution in the past and extreme hydrological events, both droughts and floods, which have increasingly affected this part of the Danube in the last decades. The conserved hydrological connection between various biotopes along the river-floodplain gradient seems crucial in maintaining high phytoplankton diversity. Accordingly, conserving natural flooding is mandatory to maintain high biodiversity in complex and dynamic river-floodplain systems.

Spatiotemporal Variations in Urban Wetlands in Kazakhstan: A Case of the Taldykol Lake System in Astana City

Acquiring a comprehensive understanding of the spatiotemporal dynamics of urban wetlands in Kazakhstan is crucial for their effective preservation and sustainable urban development. Our findings identify past and present Land Use Land Cover (LULC) in the capital city, providing policymakers with scientific evidence for improved management. Using remote sensing and Geographic Information System (GIS) techniques, this study examines the spatiotemporal changes in the Taldykol catchment area during the rapid development of Astana. In 1992, over 90% of the catchment area was grassland and vegetation. By 2022, 30% of the area became barren land. Urban areas increased by 127%, and water areas decreased by 24%. The most significant changes occurred in lakes Taldykol and Kishi Taldykol, whose areas shrank by 91% and 54%, respectively. The near-disappearance of the Taldykol wetlands is likely to contribute to rising land surface temperatures (LST), decreased natural flood control capacity, reduced biodiversity, and diminished recreational opportunities. The fate of Taldykol lakes underscores the urgent need to raise public awareness about the role of wetlands in Kazakhstan’s ecosystems and take action to preserve urban wetlands.

Dam regulation alters the spatio-temporal delivery of organic carbon along the Yellow River

Global river damming has significantly altered the riverine hydrodynamics and organic carbon (OC) delivery along the Land-to-Ocean Aquatic Continuum (LOAC). The Yellow River, one of the largest rivers in the world, has been under perturbation and fragmentation by dam construction. In this study, we quantified particulate OC (POC) and dissolved OC (DOC) fluxes, on daily-monthly-annual timescales, to explore the effects of dam-triggered perturbations on OC delivery in the Yellow River. We found that the “natural” seasonal delivery of OC upstream of the Xiaolangdi (XLD) reservoir had shifted to a heavily dam-regulated pattern downstream of the XLD reservoir. The dam-oriented Water-Sediment Regulation increased the periodic export of OC to the sea in June and July, as opposed to the natural flood season upstream of the XLD reservoir. The dam-modulated annual and inter-annual export of OC, from the Yellow River to the sea, is also teleconnected by El Niño/Southern Oscillation (ENSO) events. Historically known for its high POC flux, the Yellow River has seen a decline in POC/DOC ratios over the recent decades due to dam regulation. The dam-driven changes in organic carbon delivery along the Yellow River will continue to affect carbon cycling in its estuary and marginal seas.

A MAP-based approach to identify the social vulnerability to flood hazard in states adjacent to Mexican Gulf

The impact of floods can significantly differ based on the local circumstances. The severity of the impact caused by a natural flood in one area compared to another depends on the distinct vulnerability factors present within the affected community, encompassing cultural, social, and economic aspects. Understanding a society's capacity to anticipate, adapt to, endure, and recover from the effects of natural floods relies on evaluating its social vulnerability, which is closely connected with potential risks and community resilience. This study adopts a framework that can analyze the interaction between natural hazards and social factors and is flexible to be applied to different geographic locations. This framework encompasses flood hazards and social vulnerability within the scope of flood risk reduction. This paper explores how social vulnerability can be integrated into the analysis of flood risks within the states adjacent to the Mexican Gulf. Initially, social components are selected and applied to measure and map the Social Vulnerability Index (SVI). Next, a MAP-based methodology is adopted to identify the spatial variability of social vulnerability concerning flood hazards. Then, a risk matrix is developed and the classifications on SVI map are aligned with those on a flood hazard map; provided by the Federal Emergency Management Agency (FEMA). This led to the development of a qualitative social vulnerability exposure map to flood hazards, emphasizing regions marked by high levels of both flood risk and social vulnerability. The findings of this study highlight the importance of integrating social vulnerability into flood risk mitigation policies and emergency management, and planning.

Natural Flood Management Through Peatland Restoration: Catchment‐Scale Modeling of Past and Future Scenarios in Glossop, UK

AbstractField‐scale experiments have shown the Natural Flood Management (NFM) potential of peatland restoration. The likelihoods of effectiveness are yet unknown at scales and storms large enough to impact human lives. Using GMD‐TOPMODEL, we upscale a rare Before‐After‐Control‐Intervention empirical data set to a 25 km2 catchment with >600 properties at flood‐risk, and test storms of up to a 1,000‐year return period (RP). Under these scales/storms, we find that it is not necessary (nor feasible) to delay the outlet flow‐peak to meaningfully attenuate it. Enhancing catchment “kinematic” storage, for example, through restoration, can be sufficient to reduce flow magnitudes without detectable changes to peak‐flow timing. NFM benefit increases exponentially with restoration area size under smaller storms, but linearly under larger storms. At RP ≤ 100 years, longer‐lasting frontal‐type storms are more challenging to defend against via NFM, but at RP > 100 years shorter‐duration convectional‐type events become more challenging. In the order of 1,000–10 years storms: (a) revegetating the bare‐peat areas in 15% of the catchment is 31%–61% likely to reduce peak‐flows by >5%; (b) revegetating & damming the erosion gullies in ∼20% of the catchment is 42%–71% likely to reduce peak‐flows by >5%; (c) Growth of Sphagnum in the dammed gullies of ∼20% and ∼40% of the catchment increase the likelihoods of >5% peak reductions to 65%–86% and 90%–98%, respectively. The numerical evidence of significant NFM benefit due to Sphagnum re‐establishment is an important finding, because it shows that meaningful flood‐risk mitigation in headwater catchments under scales/storms relevant to communities at risk can be delivered alongside other ecosystem benefits of Sphagnum re‐establishment.

Contaminant mobilization from the vadose zone to groundwater during experimental river flooding events

Natural river flooding events can mobilize contaminants from the vadose zone and lead to increased concentrations in groundwater. Characterizing the mass and transport mechanisms of contaminants released from the vadose zone to groundwater during these recharge events is particularly challenging. Therefore, conducting highly-controlled in-situ experiments that simulate natural flooding events can help increase the knowledge of where contaminants can be stored and how they can move between hydrological compartments. This study specifically targets uranium pollution, which is accompanied by high sulfate levels in the vadose zone and groundwater. Two novel experimental river flooding events were conducted that utilized added non-reactive halides (bromide and iodide) and 2,6-difluorobenzoate tracers. In both experiments, about 8 m3 of traced water from a nearby contaminant-poor river was flooded in a 3-m diameter basin and infiltrated through the vadose zone and into a contaminant-rich unconfined aquifer for an average of 10 days. The aquifer contained 13 temporary wells that were monitored for solute concentration for up to 40 days. The groundwater analysis was conducted for changes in contaminant mass using the Theissen polygon method and for transport mechanisms using temporal moments. The results indicated an increase in uranium (21 and 24%), and sulfate (24 and 25%) contaminant mass transport to groundwater from the vadose zone during both experiments. These findings confirmed that the vadose zone can store and release substantial amounts of contaminants to groundwater during flooding events. Additionally, contaminants were detected earlier than the added tracers, along with higher concentrations. These results suggested that contaminant-rich pore water in the vadose zone was transported ahead of the traced flood waters and into groundwater. During the first flooding event, elevated concentrations of contaminants were sustained, and that chloride behaved similarly. The findings implied that contaminant- and chloride-rich evaporites in the vadose zone were dissolved during the first flooding event. For the second flooding event, the data suggested that the contaminant-rich evaporites continued to dissolve whereas chloride-rich evaporites were previously flushed. Overall, these findings indicated that contaminant-rich pore water and evaporites in the vadose zone can play a significant role in contaminant transport during flooding events.

Walking With/In Place: The Walking Turn In Socially Engaged Public Art From Aotearoa New Zealand

This article first suggests that there has been a “Walking Turn” in contemporary socially engaged public art and then considers critically how these practices might be best framed and understood in the context of Aotearoa. There has been a multitude of walking-based artworks in Aotearoa since the second half of the 2010s to the present. In the wake of the global pandemic and natural flooding and cyclone disasters in Aotearoa that soon followed, “going out for a walk” has been repeatedly problematized and reframed for most citizens. This article seeks to establish a theoretical framework that is responsive to Indigenous as well as posthumanist discourse, through which we might best consider walking art practices in Aotearoa. To do this, the concept of walking “with/in” place is employed as an entry point. Drawing on research interviews, a number of culturally informed concepts related to walking are examined alongside notions of countermapping and countermonument. The artwork analysis considers the decolonial, counterneoliberal, and regenerative principles underlining these practices. The artworks discussed engage in histories and contemporary politics of place and can be characterized by quietude, humility, and hyperlocality.

Urban development and the loss of natural streams leads to increased flooding

Developing countries with hard pressed economies and a rapidly growing population have a myriad of issues to face. Karachi is one of the largest cities of Pakistan and is rapidly growing. The city has been hit by floods in the year 2016, 2018, 2019 and 2020, recently. Since the early 1990s Karachi has seen a rapid spike in development and in the process many natural streams have been built over. This has led reduced space for rainwater runoff and has created problems for urban flood managers. To ascertain this, topographic records of 1940s and 1980s and Landsat imagery of 2000, 2008, 2015 and 2020 were used to map historical urban extent. Sentinel—1, Synthetic Aperture Radar (SAR) imagery was used to extract flooded areas during 2015, 2017, 2019 and 2020 floods. In the year 2020, 64.3 km2 of area was flooded which was the highest. There has been a growth of 286% in urban area observed between 1980 and 2000. The city was built with several natural flood water carrying streams, north and west of it. It was found that that out of 3600 km of these streams, 870 km of streams have either been blocked or removed and a 100% in core urban area. DEM of difference (DOD) prepared by subtracting 1945 DEM from SRTM DEM indicated that most of embankments along these streams were in the areas that show erosion in DOD surface, thus explaining the expansion of built areas along historical stream channels. Forcing floods to enter these built areas.

Global, regional and national trends and impacts of natural floods, 1990-2022.

To assess global, regional and national trends in the impact of floods from 1990 to 2022 and determine factors influencing flood-related deaths. We used data on flood disasters from the International Disaster Database for 1990-2022 from 168 countries. We calculated the annual percentage change to estimate trends in the rates of people affected and killed by floods by study period, World Health Organization (WHO) region, country income level and flood type. We used multivariable logistic regression analysis to assess the factors associated with death from floods. From 1990 to 2022, 4713 floods were recorded in 168 countries, which affected > 3.2 billion people, caused 218 353 deaths and were responsible for more than 1.3 trillion United States dollars of economic losses. The WHO Western Pacific Region had the most people affected by floods (> 2.0 billion), accounting for 63.19% (2 024 599 380/3 203 944 965) of all affected populations. The South-East Asia Region had the most deaths (71 713, 32.84%). The African and Eastern Mediterranean Regions had the highest number of people affected and killed by floods per 100 000 population in 2022. The odds of floods causing more than 50 deaths were significantly higher in low-income countries (adjusted odds ratio: 14.34; 95% confidence interval: 7.46 to 30.04) compared with high-income countries. Numbers of people affected and mortality due to floods declined over time. Despite the decreases in populations affected and deaths, floods still have a serious impact on people and economies globally, particularly in lower-income countries. Action is needed to improve disaster risk management and flood mitigation.

Real-time biological early-warning system based on freshwater mussels’ valvometry data

Abstract. Quantifying the effects of external climatic and anthropogenic stressors on aquatic ecosystems is an important task for scientific purposes and management progress in the field of water resources. In this study, we propose an innovative use of biotic communities as real-time indicators, which offers a promising solution to directly quantify the impact of these external stressors on the aquatic ecosystem health. Specifically, we investigated the influence of natural river floods on riverine biotic communities using freshwater mussels (FMs) as reliable biosensors. Using the valvometry technique, we monitored the valve gaping of FMs and analysed both the amplitude and frequency. The valve movement of the FMs was tracked by installing a magnet on one valve and a Hall effect sensor on the other valve. The magnetic field between the magnet and the sensor was recorded using an Arduino board, and its changes over time were normalised to give the opening percentage of the FMs (how open the mussels were). The recorded data were then analysed using continuous wavelet transform (CWT) analysis to study the time-dependent frequency of the signals. The experiments were carried out both in a laboratory flume and in the Paglia River (Italy). The laboratory experiments were conducted with FMs in two configurations: freely moving on the bed and immobilised on vertical rods. Testing of the immobilised configuration was necessary because the same configuration was used in the field in order to prevent FMs from packing against the downstream wall of the protection cage during floods or from breaking their connection wires. These experiments allowed us to verify that immobilised mussels show similar responses to abrupt changes in flow conditions as free mussels. Moreover, immobilised mussels produced more neat and interpretable signals than free-moving mussels due to the reduced number of features resulting from movement constraints. We then analysed the response of 13 immobilised mussels under real river conditions during a flood on 31 March 2022. The FMs in the field showed a rapid and significant change in valve gap frequency as the flood escalated, confirming the general behaviour observed in the laboratory in the presence of an abrupt increase in the flow. These results highlight the effectiveness of using FMs as biosensors for the timely detection of environmental stressors related to natural floods and emphasise the utility of CWT as a powerful signal-processing tool for the analysis of valvometry data. The study proposes the integration of FM valvometry and CWT for the development of operational real-time biological early-warning systems (BEWSs) with the aim of monitoring and protecting aquatic ecosystems. Future research should focus on extending the investigation of the responsiveness of FMs to specific stressors (e.g. turbidity, temperature, and chemicals) and on testing the applications of the proposed BEWSs to quantify the impact of both natural stressors (e.g. heat waves and droughts) and anthropogenic stressors (e.g. hydropeaking, reservoir flushing, and chemical contamination).

Strategic Integration of Catchment Level Natural and Structural Methods of Sustainable Flood Management: A Case Study of River Wharfe Catchment Area

Water has a crucial place in the advent of humankind the flourishing of mega population centres, and is an essential source of food, water transportation, and irrigation. The anthropogenic activities in taming the natural water streams to the optimum benefit of human beings disturb natural flood plains, ecology and habitat. The channelisation of streams and hydromodifications in dams, barrages or reservoirs result in climatic variations locally/ regionally and impact transborder stream flow. Researchers have been endeavouring to restore the flood plains to their natural conditions. Still, huge hydromodifications and the development of megacities right in the flood plains or adjacent to the streams have resulted in irreversible disturbances to the natural lay of ground/ landscape. Therefore, to avoid flooding disasters, further structural interventions are undertaken to augment the natural flood prevention methods using advanced materials like cement concrete, steel, and polymers rather than increasing the emissions of greenhouse gases. Considering the strategic necessity of engineering structures as an integrated catchment level solution to augment the natural methods, the researchers/ engineers are now focussing on the use of sustainable, eco-friendly materials and demountable/ hydraulic structures to minimise the carbon footprints of hydromodifications and to decrease the obstruction to the natural flow of streams by using the flood prevention structures/ gates/ walls/ reservoirs only in case of disastrous flooding and otherwise keeping them unemployed during normal stream discharges. This study has been used to review sustainable flood management using natural and structural techniques in the Wharf River catchment in the UK, reviewing the existing research/ flood management schemes giving the pictorial coverage. The study suggests that natural flood management techniques have restricted application parameters and must be augmented by engineering structures to achieve effective flood management against heavy flooding. Low CO2 embodied greener infrastructure structural materials containing supplementary cementitious materials (SCMs) can be a beneficial option for an environmentally friendly flood management strategy.

Broadleaf afforestation impacts on terrestrial hydrology insignificant compared to climate change in Great Britain

Abstract. Widespread afforestation has been proposed internationally to reduce atmospheric carbon dioxide; however, the specific hydrological consequences and benefits of such large-scale afforestation (e.g. natural flood management) are poorly understood. We use a high-resolution land surface model, the Joint UK Land Environment Simulator (JULES), with realistic potential afforestation scenarios to quantify possible hydrological change across Great Britain in both present and projected climate. We assess whether proposed afforestation produces significantly different regional responses across regions; whether hydrological fluxes, stores and events are significantly altered by afforestation relative to climate; and how future hydrological processes may be altered up to 2050. Additionally, this enables determination of the relative sensitivity of land surface process representation in JULES compared to climate changes. For these three aims we run simulations using (i) past climate with proposed land cover changes and known floods and drought events; (ii) past climate with independent changes in precipitation, temperature, and CO2; and (iii) a potential future climate (2020–2050). We find the proposed scale of afforestation is unlikely to significantly alter regional hydrology; however, it can noticeably decrease low flows whilst not reducing high flows. The afforestation levels minimally impact hydrological processes compared to changes in precipitation, temperature, and CO2. Warming average temperatures (+3 °C) decreases streamflow, while rising precipitation (130 %) and CO2 (600 ppm) increase streamflow. Changes in high flow are generated because of evaporative parameterizations, whereas low flows are controlled by runoff model parameterizations. In this study, land surface parameters within a land surface model do not substantially alter hydrological processes when compared to climate.

Optimizing Infragravity Wave Attenuation to Improve Coral Reef Restoration Design for Coastal Defense

Coral reefs are effective natural flood barriers that protect adjacent coastal communities. As the need to adapt to rising sea levels, storms, and environmental changes increases, reef restoration may be one of the best tools available to mitigate coastal flooding along tropical coastlines, now and in the future. Reefs act as a barrier to incoming short-wave energy but can amplify low-frequency infragravity waves that, in turn, drive coastal flooding along low-lying tropical coastlines. Here, we investigate whether the spacing of reef restoration elements can be optimized to maximize infragravity wave energy dissipation while minimizing the number of elements—a key factor in the cost of a restoration project. With this goal, we model the hydrodynamics of infragravity wave dissipation over a coral restoration or artificial reef, represented by a canopy of idealized hemispherical roughness elements, using a three-dimensional Navier–Stokes equations solver (OpenFOAM). The results demonstrate that denser canopies of restoration elements produce greater wave dissipation under larger waves with longer periods. Wave dissipation is also frequency-dependent: dense canopies remove wave energy at the predominant wave frequency, whereas sparse canopies remove energy at higher frequencies, and hence are less efficient. We also identify an inflection point in the canopy density–energy dissipation curve that balances optimal energy losses with a minimum number of canopy elements. Through this work, we show that there are an ideal number of restoration elements per across-shore meter of coral reef flat that can be installed to dissipate infragravity wave energy for given incident heights and periods. These results have implications for designing coral reef restoration projects on reef flats that are effective both from a coastal defense and costing standpoint.

Review of the Quantification of Aeolian Sediment Transport in Coastal Areas

Coastal dunes, formed and shaped by aeolian sediment transport, play a crucial role in ecosystem services and act as natural flood and coastal erosion defenses. This paper delves into theoretical equations and numerical models predicting sediment transport. Numerical models like cellular automata, XBeach-DUNA, the coastal dune model, and others are analyzed for their ability to simulate dune morphology, erosion processes, and vegetation impacts accurately. Evaluated are field observation and measurement techniques, such as sand traps, impact sensors, and optical sensors, for their precision in quantifying aeolian dynamics. Further examined is the effectiveness of vegetation and fencing in dune stabilization, noting species-specific responses and the influence of fence design on sediment accumulation. These tools offer insights into optimizing aeolian sediment management for coastal protection. By conducting a systematic review and connecting theoretical, empirical, and modeling findings, this study highlights the complex challenge of measuring and managing aeolian sediment transport and proposes integrated strategies for enhancing coastal dune resilience against the backdrop of climate change and erosion. This study’s objectives to bridge gaps in current understanding are met, highlighting the need for a multidisciplinary approach to coastal dune management and conservation, especially combining wind- and wave-driven processes.

Effects of natural flood management woody dams on benthic macroinvertebrates and benthic metabolism in upland streams: Importance of wood‐induced geomorphic changes

AbstractNatural Flood Management (NFM) aims to reduce flood hazard by working with nature and is gaining prominence worldwide. One particular NFM technique involves the use of channel‐spanning woody dams that maintain a clearance height above baseflow. These dams function by increasing channel roughness during high flows and by forcing excessive water onto the floodplain. Whether these dams provide additional benefits to nature remains unclear. While there are many existing studies on natural in‐stream wood structures, very few have documented the impact of NFM woody dams in particular. This study adopted a multidisciplinary approach and a Before–After Control–Impact (BACI) research design to assess whether NFM woody dams installed in a small upland catchment had driven changes in benthic macroinvertebrate assemblages and benthic metabolic activities through the geomorphic changes that they had created. Statistical results indicate that macroinvertebrate density, richness, and diversity did not show any difference between stream reaches with and without NFM woody dams. The metrics were generally not related to grain‐size parameters and volumes of sediments eroded or deposited. However, individual genera such as Baetis and Rhithrogena became more dominant in the control reach towards the end of the study period, likely due to the higher flow velocities and coarser sediments there resulting from the lack of flow resistance in the absence of NFM woody dams. Rates of benthic respiration (but not rates of photosynthesis) were consistently significantly higher in woody dam reaches than in control reaches, likely due to the presence of patches of finer sediments in the former.