Storm events

This paper presents the benefits of multiplying environmental indicators to better understand the impacts of past storm events on the environment. It aims to describe the methodological approaches used to reconstruct past extreme events from washover deposits, at the three main temporal scales used in scientific bibliography: i) the long timescale (Holocene, since 12 000 years BP), ii) the meso timescale (for the last millenary) and iii) the short timescale (Anthropocene, for the last centuries). This methodology is based on a “multiproxy” analysis using sedimentology, geochemistry and various methods of isotope dating. Linking these methods with other disciplines such as history, archaeology and meteorology leads us to confirm with great certainty the existence of these extreme events, and to expose their impacts on the environment and on past coastal societies. These different approaches enable us to enhance and refine our knowledge of coastal hazards, but also to apprehend possible storm influences in the context of climate change.

Flevoland (central Netherlands) is an area of long-term discontinuous deposition that has been reclaimed from the Zuiderzee in the 20th century. Before the reclamation, the Zuiderzee had been in a phase of enlargement, threatening inhabitants on the islands and the shores, since the Medieval Period. During this phase, a surficial clay cover was deposited on the island of Schokland (World Heritage Site: Noordoostpolder, northern Flevoland). We have studied the clay sequence in order to reconstruct the island’s flooding history during the last 1200 years. The depositional history of the youngest clay deposit on Schokland is inferred from a literature study, analyses of a digital elevation model, six coring transects, three new14C accelerator mass spectrometry (AMS) dates and laboratory analyses. The laboratory analyses include thermogravimetric analysis, grain-size end-member modelling (unmixing grain-size distributions), foraminifera, bivalves and ostracods. The geological data were ...

This paper reviews the reconstruction of European Atlantic storm events with the contribution of a new stormy reconstruction in its central part. Three marsh environments on the island of Yeu were chosen to identify disturbing storm events from the Mid- to Late Holocene with vibracore sampling, radiocarbon dating and sedimentary analysis. Nine probable intervals of high energy deposition in these low-transport-activity environments are estimated: 600–500, near 1590, 2100–1950, 2850–2350, 3500–3270, 5400–5370, 6650–6510, near 7000 and between 7670 and 7470 calibrated years before present (cal y BP). By comparison with sedimentological paleostorm studies, we confirm six European Atlantic storm events estimated at near 600–300, 1700–1100, 2900–2500, 3500–3300, 5500–5100 and 7700–7100 cal y BP, corresponding to worldwide Holocene cooling climatic periods. A comparison with other storminess reviews of worldwide main stormy coasts shows that Holocene storms can increase during global cooling periods in the northern hemisphere.

Flevoland (central Netherlands) is an area of long-term discontinuous deposition that has been reclaimed from the Zuiderzee in the 20th century. Before the reclamation, the Zuiderzee had been in a phase of enlargement, threatening inhabitants on the islands and the shores, since the Medieval Period. During this phase, a surficial clay cover was deposited on the island of Schokland (World Heritage Site: Noordoostpolder, northern Flevoland). We have studied the clay sequence in order to reconstruct the island’s flooding history during the last 1200 years. The depositional history of the youngest clay deposit on Schokland is inferred from a literature study, analyses of a digital elevation model, six coring transects, three new14C accelerator mass spectrometry (AMS) dates and laboratory analyses. The laboratory analyses include thermogravimetric analysis, grain-size end-member modelling (unmixing grain-size distributions), foraminifera, bivalves and ostracods. The geological data were ...

High-frequency (30 min) data was used to investigate storm responses in two subtropical
catchments in the Brazilian Atlantic Forest. We measured discharge, turbidity and conductivity in a 30 km2 subsurface-dominated catchment (2012-2013) and in a 48 km2 groundwater-dominated catchment (2014-2016). Conductivity was dominated by elements associated with geochemical weathering or atmospheric deposition, but also nutrients such as nitrate. Turbidity was a proxy for suspended sediment. Results showed similar dominant storm event patterns in both catchments. The dominant pattern for turbidity was a positive C-Q relationship with clockwise hysteresis, suggesting a nearby source, while the dominant pattern for conductivity was a negative C-Q relationships with clockwise hysteresis, suggesting storage of solutes in deep groundwater and distant sources (hillside). The negative C-Q pattern for conductivity was stronger and the hysteresis wider in the groundwater-dominated catchment. Hydroclimatic controls were also similar between both catchments, but storm event patterns in the subsurface-dominated catchment were more strongly influenced by antecedent conditions (conditions before the event) that in the groundwater dominated catchment.