Explore the vast range of titles available.

Fluvial cross strata are fundamental sedimentary structures that record past flow and sediment transport conditions. Bedform preservation can be significantly influenced by the presence of larger‐scale topographic features that cause spatial gradients in flow. However, our understanding of the controls on cross strata preservation in the presence of a morphodynamic hierarchy is limited. Here, using high‐resolution bathymetry from a physical experiment, we quantify bedform evolution and cross strata preservation in a zone of flow expansion and deceleration. Results show that the size and celerity of superimposed bedforms decreases along the host‐bedform lee slope, leading to a systematic downstream increase in the sediment accumulation rate relative to bedform celerity. This increase in local bedform climb angle results in the preservation of a larger fraction of formative bedforms. Our results highlight the need to revise current paleohydraulic reconstruction models, and demonstrates that fluvial morphodynamic hierarchy is a fundamental determinant of sedimentary strata. Plain Language Summary Dune evolution in rivers creates inclined layers of sediment, called cross strata, that are an integral part of the rock record on Earth and Mars. The thickness distribution of cross strata is the primary means of estimating ancient flow and sediment transport conditions. Dunes exist with larger‐scale features, such as bars and larger dunes, in rivers, where a train of dunes responds to flow steering by larger‐scale features through changes in dune size and speed. However, we currently lack data to assess the influence of larger‐scale features on dune evolution and cross strata. Here, we studied dune evolution on the lee side (downstream facing slope) of a larger bedform in an experimental channel, where flow expands and slows down. Using high‐resolution data, we show that the dune size and speed decrease with downstream distance along the host‐bedform lee side. The rate of sediment build‐up relative to dune speed increases downstream, which leads to the preservation of a larger fraction of dunes in cross strata. Results suggest that cross strata preserved in the presence of larger‐scale features are common in the rock record, and we need to revise our current models for estimating past flow conditions from cross strata. Key Points We characterize bedform evolution and cross strata preservation in a zone of flow expansion and deceleration in a physical experiment Bedform size and celerity decrease along the host‐bedform lee slope, causing an increase in aggradation rate relative to bedform celerity A larger fraction of the formative bedforms is preserved as cross strata than typically assumed by paleohydraulic reconstruction models

Awareness of coastal landscapes vulnerability to both natural and man-made hazards induce to monitor their evolution, adaptation, resilience and to develop appropriate defence strategies. The necessity to transform the monitoring results into useful information is the motivation of the present paper. Usually, to this scope, a coastal vulnerability index is deduced, by assigning ranking values to the different parameters governing the coastal processes. The principal limitation of this procedure is the individual discretion used in ranking. Moreover, physical parameters are generally considered, omitting socio-economic factors. The aim of the present study is to complement a geographical information system (GIS) with an analytical hierarchical process (AHP), thus allowing an objective prioritization of the key parameters. Furthermore, in the present case, socio-economic parameters have been added to physical ones. Employing them jointly, an integrated coastal vulnerability index (ICVI) has been estimated and its effectiveness has been investigated. To show how it works, the proposed method has been applied to a portion of the Adriatic coastline, along the Apulian region in southern Italy. It has permitted to identify and prioritize the most vulnerable areas, revealing its efficacy as a potential tool to support coastal planning and management.

This contribution presents a new approach for assessing/ranking the vulnerability of beaches to mean and extreme sea level rise at regional (island) scales. It combines socio-economic information with beach erosion projections from morphodynamic models to rank beach vulnerability in a structured, ‘holistic’ manner. It involves the collation of various beach geo-spatial environmental and socio-economic data, which are then combined with erosion projections under different climatic scenarios. A Strengths–Weaknesses–Opportunities–Threats (SWOT) framework is employed for the indicator selection, and multi-criteria methods (Analytical Hierarchy Process—AHP, Technique for Order of Preference by Similarity to Ideal Solution—TOPSIS, Preference Ranking Organization Method for Enrichment Evaluations—PROMETHEE II) are then used to optimize indicator weights and rank beach vulnerability. Framework implementation in Lesvos and Kos has shown that there will be significant effects of the mean and (particularly) of the extreme sea levels on the carrying capacity and the capability of the beaches to buffer backshore assets, in the absence of appropriate adaptation measures. As the proposed approach relies on widely available information on many of the socio-economic indicators required to assess the beach’s significance/criticality, it can provide a reproducible and transferable methodology that can be applied at different locations and spatial scales.

Cartographic techniques are frequently applied for coastal mapping, but their application for the study of coastal morphodynamics is unpopular, as they only give limited parameters like plan-view, geometry, area–length measurement and lithology. On the other hand, detailed study of morphodynamics requires extra information like depthwise variation in lithology and absolute dating. Since both these techniques are expensive, cartographic techniques can be cost-effective supplementary. In the present study, morphodynamic history of Subarnarekha estuary from 7000 years BP has been interpreted applying data from cartographic techniques along with shallow wells, 14C-dating and literature survey. Geomorphologic features of the coastal plain were identified in the order of hierarchy, viz. chenier plain (first order); beach ridge complex, spit complex, chenier complexes (second order); cheniers (third order); and simplest ridge, spit, washover beach (fourth order). Following this field-investigated geological history of river dynamics (both Ganges and Subarnarekha) and sea-level changes identified by earlier researchers were merged with cartographically observed features. The studied ridge chronology provides six sequences of chenier complex development agewise, whereas geometry of spit complexes suggests chronological conversion of Subarnarekha estuary from initial wave-dominated to tide-dominated flow.