Explore the vast range of titles available.

By 2009, the Kien Giang coast, Vietnam, had experienced significant coastal erosion and mangrove degradation. Recent mitigation strategies, developed through policies, plans and mangrove planting programs have not been successful, in part because the causes of coastal erosion were not adequately identified. This paper investigates the relationship between human activities and coastal erosion in Kien Giang province. This study used mixed methods to understand the causes of coastal erosion with an emphasis on human activities. In this investigation, local communities were involved as co-investigators to explore the causes of coastal erosion in Kien Giang province. While natural factors (adverse effects of climate change and sea level rise) have been widely reported as main causes of coastal erosion, human activities initially were not recognised by local communities as significant contributors to coastal erosion and mangrove degradation. Human activities such as poor aquaculture pond construction, poor construction of new and upgraded sections of the sea dyke system, mangrove afforestation using only a single species, mangrove cutting for commercial and domestic uses, and construction of local boating channels, and the interaction of anthropogenic activities and physical processes are significant contributors to erosion. The study resulted in the awareness of the impact of community activities on the coast being improved. Knowledge gaps and necessary policy changes are identified.

We analyze the spatio-temporal dynamics of sand relocation for beach nourishment in the low-energy coastal segment north of the Port of Klaipėda, eastern Baltic Sea, under mild wave conditions, with significant wave heights below 0.9 m and water level variations from –30 to 44 cm with respect to the long-term average. In summer 2022, about 180 000 m3 of sand was added approximately 120 m from the shore at water depths of 2–3.5 m to form a 750 m long underwater bar. Sand relocation is evaluated based on repeated water depth measure ments along 114 cross-shore coastal profiles. Some sand was rapidly transported to greater depths, down to about 6 m, even though wave conditions were particularly mild. The pre dominant sand motion was directed offshore, and characteristically for the area, wave-driven sediment transport was directed to the north. The analysis confirms that even very mild wave conditions can substantially relocate large volumes of deposited sand in shallow water, both offshore and onshore, from its original location during the initial adjustment phase following nourishment.

Loads exerted to the seabed by short-crested wind-seas with a wide directional spread have extensive spatio-temporal variability. We quantify this variability in terms of near-bed water speed using an array of nine high-resolution hydromast devices for recording pressure and water velocity in the range of 0.12–1 m/s mounted at a distance of 10 m from each other on a rigid rectangular frame of 20 × 20 m in approximately 4 m deep water and 700 m from the eastern shore of the Gulf of Riga near Skulte (Latvia) in August–September 2022. This array is complemented by an acoustic Doppler velocimeter (ADV). The average background current is very weak, approximately 0.003 m/s in the measurement location. The empirical distributions of velocity components are symmetric but greatly deviate from the expected Gaussian distribution. The empirical distributions of water speeds follow an exponential distribution rather than a Rayleigh or Forristall distribution. This shape of the distributions appears in the range of 0.2–0.7 m/s while the maximum speed reaches 1.22 m/s. The rate parameter (inverse scale parameter) varies almost by a factor of two in recordings by different devices. The recordings make it possible to identify wakes of vessels entering to or departing from the Port of Skulte.

Optimizing the location of wind and photovoltaic solar power plants is a significant environmental management problem. The effectiveness of the site selection process for renewable energy systems (RES) could be strengthened by flexible spatial and environmental planning strategies using decision support systems (DSS) to critically identify the most productive, environmentally friendly and acceptable sites for the production of sustainable and reliable wind and solar energy. This study discusses hybrid DSS, using multi-criteria evaluation based on the analytical hierarchy process (AHP), a geographical information system (GIS), fuzzy logic, and a weighted linear combination (WLC) approach to determine optimal locations for renewable energy generation infrastructure. In the first stage, the most decisive factors for evaluating the site suitability were identified, based on experts’ opinions. Next, raster layers of ecological and socioeconomic sub-criteria were prepared GIS software. After incorporating the raster maps of each parameter, fuzzy membership functions were applied to normalize each raster layer between 0 and 1. The relative weights of different indicators were calculated using super decision software. Prioritizing vital elements were performed using AHP. In the final stage, the WLC approach was utilized to amalgamate layers in the GIS environment, which afforded the final site suitability maps. In Isfahan Province, Iran, 26% of the land area was found to be highly suitable for solar farms with 18% being highly suitable for wind farms. The results illustrate that using and comparing the results from combinations of computer-based DSS are more likely to result in better decisions than using individual DSS tools for the determination of the most suitable sites for RES location.Graphic abstract

Soomere, T.; Bagdanavičiūtė, I.; Barzehkar, M., and Parnell, K.E., 2024. Towards implementing water level variations into coastal vulnerability indexes in microtidal seas. 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. 48-52. Charlotte (North Carolina), ISSN 0749-0208. We explore the potential of several quantities that reflect the magnitude of local water level variations to characterize the contribution of water level into estimates of the Coastal Vulnerability Index (CVI) in microtidal seas hosting substantial water level variations. The analysis is based on sea level time series reconstructed with the Rossby Centre Ocean model for 1961–2005 and an early version of the RCA4-NEMO model for 1961–2009. The projections of extremely high and low sea levels for return periods of 10 and 50 yrs are constructed using sea level extremes in 12 month long time intervals, block maximum method and several extreme value distributions. The focus is on the relatively straight Baltic proper shore of Lithuania. We show that projected extremely high and low sea levels once in 10 and 50 yrs provide certain independent information about vulnerability along this coastal segment. The use of a larger number of parameters shrinks the range of the output values of the CVI. The outcome provides important input for coastal management but also suggests that more elaborated quantities might better characterize the impact of varying water levels on coastal vulnerability.

Rätsep, M.; Parnell, K.E., and Soomere, T., 2020. Detecting ship wakes for the study of coastal processes. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1258–1262. Coconut Creek (Florida), ISSN 0749-0208. Wakes from contemporary vessels may affect, and in some places dominate, coastal processes in the vicinity of major shipping lanes. The analysis of the properties and impact of wakes has generally been restricted to wakes that can be visually observed in raw data. In this work, spectral analysis of the time series of single-point measurements of water surface elevation from Tallinn Bay is used to highlight the structure of ship wakes using a Short Time Fourier Transform. This method makes it possible to determine the speed and distance of a vessel from the measurement site. Wakes are detected using an algorithm based on Gabor multipliers. The results are compared with vessel passages retrieved from the Automatic Identification System (AIS) data. The algorithm detects the majority of ship wakes that can be visually recognized in spectrograms and misses only those with low signal to noise ratio or those in close proximity to another vessel wake. The calculated speed and distance are consistent with the AIS data except for high-speed vessels sailing at ≥30 knots. The results indicate that by using these techniques the detection of vessel wakes from a single-point wave record is achievable under favorable weather conditions. The methods provide an option for mitigation of the impact of ship wakes in semi-enclosed water bodies.

Large in situ measured ship-induced depression waves (Bernoulli wakes) in the Malamocco-Marghera industrial channel of the Venice Lagoon are interpreted as long-living strongly nonlinear Riemann (simple) waves of depression. The properties of these depressions are numerically replicated using nonlinear shallow water theory and the CLAWPACK software. The further behaviour of measured depressions is analysed by means of replicating the vessel-induced disturbances with the propagation of initially smooth free waves. It is demonstrated that vessel-driven depressions of substantial height (> 0.3 m) often propagate for more than 1 km from the navigation channel into areas of the lagoon of approximately 2 m water depth. As a depression wave propagates into the lagoon, its front slope becomes gradually less steep, but the rear slope preserves an extremely steep bore-like appearance and the amplitude becomes almost independent of the initial properties of the disturbance. Analysis suggests that even modest ships in terms of their size, sailing speed, and blocking coefficient may generate deep depressions that travel as compact and steep entities resembling asymmetric solitary waves over substantial distances into shallow water adjacent to navigation channels. Their impact may substantially increase the environmental impact of ship wakes in this and similar water bodies.

Parnell, K.E. and Smithers, S.G., 2020. Regional and local variability in coastal processes in Torres Strait, Australia, and its importance for climate change planning. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 616–620. Coconut Creek (Florida), ISSN 0749-0208. In small island states or regions, climate change planning is frequently undertaken at a country or regional level, and it is assumed that problems are common and that remedial actions can be widely applied. Community members observe treatments such as seawalls elsewhere and demand similar interventions even though they may be inappropriate. Torres Strait lies between mainland Australia and Papua New Guinea and has communities on a diverse range of islands including low muddy, coral cay, volcanic and continental island types. Approaches to solving problems caused by changing coastal processes on these varied shorelines are discussed at scales from regional to specific sites. Torres Strait has two distinct wind seasons which influence wave-driven processes and lead to seasonally reversing alongshore sediment transport, with shoreline dynamics also controlled by coastal orientation and the beach / reef flat interactions. The low muddy islands have limited management options, requiring shore protection and elevation. Shorelines on coral cay islands and the volcanic and continental islands change shape seasonally. In these settings, planning must allow for the seasonal shoreline adjustments, with structural treatments to manage longer-term shoreline trends used only to protect high-value assets and important cultural sites where alternative management responses are not possible.

Monitoring vessel traffic in coastal regions is a key element of maritime security. For this reason, additional ways of detecting moving vessels are explored by using the unique structure of their wake waves based on pressure measurements at the seabed. The experiments are performed at a distance of about 2 km from the sailing line using novel multisensor devices called “hydromasts” that track both pressure and near-bed water flow current velocities. The main tool for the analysis is a windowed Fourier transform that produces a spectrogram of the wake structure. It is shown that time series from the pressure sensors, measured at a frequency of 100 Hz, 0.2 m above the seabed are a valid source of input data for the spectrogram technique. This technique portrays the properties of both divergent and transverse waves with an accuracy and resolution that is sufficient for the evaluation of the speed and distance of the detected vessels from the measurement device. All the detected passings are matched with vessels using automatic identification system (AIS) data. The use of several time series from synchronized multisensor systems substantially suppresses noise and improves the quality of the outcome compared to one-point measurements. Additional information about variations in the water flow in wakes provides a simple and reasonably accurate tool for rapid detection of ship passages.