Zoek binnen publicaties
Global modeling of tropical cyclone storm surges using high-resolution forecasts
We assess the suitability of ECMWF Integrated Forecasting System (IFS) data for the global modeling of tropical cyclone (TC) storm surges. We extract meteorological forcing from the IFS at a 0.225° horizontal resolution for eight historical TCs and simulate the corresponding surges using the global tide and surge model. Maximum surge heights for Hurricanes Irma and Sandy are compared with tide gauge observations, with R2-values of 0.86 and 0.74 respectively. Maximum surge heights for the other TCs are in line with literature. Our case studies demonstrate that a horizontal resolution of 0.225° is sufficient for the large-scale modeling of TC surges. By upscaling the meteorological forcing to coarser resolutions as low as 1.0°, we assess the effects of horizontal resolution on the performance of surge modeling. We demonstrate that coarser resolutions result in lower-modeled surges for all case studies, with modeled surges up to 1 m lower for Irma and Nargis. The largest differences in surges between the different resolutions are found for the TCs with the highest surges. We discuss possible drivers of maximum surge heights (TC size, intensity, and coastal slope and complexity), and find that coastal complexity and slope play a more profound role than TC size and intensity alone. The highest surges are found in areas with complex coastlines (fractal dimension > 1.10) and, in general, shallow coastlines. Our findings show that using high-resolution meteorological forcing is particularly beneficial for areas prone to high TC surges, since these surges are reduced the most in coarse-resolution datasets.
Validatie van Steentoets 2010 : stabiliteit van steenzettingen
In het kader van de toetsing van de waterkeringen zoals voorgeschreven in de Waterwet dienen ook steenzettingen elke zes jaar getoetst te worden. Volgens de VTV2006 moet dit uitgevoerd worden met het Excel-programma Steentoets (Klein Breteler, 2011). Daarnaast kan Steentoets gebruikt worden als hulpmiddel voor het ontwerpen van steenzettingen. Het programma is ten behoeve van de toepassing in de derde toetsronde uitgebreid gevalideerd aan de hand van Deltagootproeven en er is een analyse uitgevoerd van de trends in de resultaten als parameters worden gewijzigd (Klein Breteler, 2009). De toenmalige versie van Steentoets betrof Steentoets2008, versie 0.80. Sindsdien is de kennisontwikkeling op het gebied van de stabiliteit van steenzettingen verdergegaan. Deze nieuwe ontwikkelingen hebben geleid tot verbeteringen in het rekenmodel. Om te kunnen beoordelen of deze ontwikkelingen nog steeds in lijn zijn met de beschikbare resultaten van grootschalig modelonderzoek is in deze rapportage opnieuw een vergelijking gemaakt tussen de resultaten van Steentoets en de beschikbare grootschalige modelproeven. Daar is nu Steentoets2010, versie 1.09, voor gebruikt. Tevens zijn de trends weer geanalyseerd en is beoordeeld of deze realistisch zijn.
Rapportage geologisch onderzoek zoekgebieden Noordzee zandwinning
In 2016, is in opdracht van RWS Kustlijnzorg en Stichting LaMER, een grootschalige geologisch onderzoek uitgevoerd voor het vaststellen van de geologische opbouw van 105 potentiële zoekgebieden voor de winning van suppletie- en ophoogzand. Het doel van het geologisch onderzoek was om inzicht te krijgen 1) in het voorkomen van stoorlagen die de effectieve winbaarheid van het zand in de weg staan en 2) in de kwaliteit van het beschikbare zand. Daarnaast is gekeken naar de aanwezige slibconcentraties in de ondergrond, ten behoeve van het modellenonderzoek naar de ecologische effecten van een toename van de slibconcentraties in de Noordzee als gevolg van zandwinning. Het voorliggende onderzoek is onderdeel van het MEP 2014-2017 en vormt daarmee input voor het MER 2018-2027. De zoekgebieden worden definitief vastgesteld in het MER en vormen de basis voor de ontgrondingsvergunningen voor de komende 10 jaar.
R&D highlights Deltares edition 2018
Deltares aims to make the research and development results (R&D) more accessible to the public and the private sector. The chapters in this 2018 report follow the structure of the six issues that are central to the Deltares mission: Enabling technologies; Delta infrastructure; Water and subsoil resources; Adaptive delta planning; Ecosystems and environmental quality; Flood risk.
The relationship between inundation duration and Spartina alterniflora growth along the Jiangsu coast, China
The above-ground biomass of Spartina alterniflora salt marsh meadows is influenced by numerous interacting factors, among them elevation, tidal range and inundation duration. Bio-geomorphological models make use of either linear or quadratic equations, but it is important to be aware that the variables are area specific and hence not generic. In order to explore the vegetation growth pattern and its influencing factors along the Jiangsu coast, China, field surveys were conducted in two typical S. alterniflora marshes along the coast of Dafeng and Rudong. To combine the influence of elevation and the effect of tidal range, the inundation ratio (IR) is introduced as a novel parameter, which is the ratio between inundation duration and the duration of the whole tidal period concerned. The relationship between above-ground biomass and IR can be expressed by a quadratic equation. The optimal inundation ratio for S. alterniflora along the Jiangsu coast ranges from 0.21 to 0.26, which is much lower than, for example, that for the marsh of North Inlet (0.35), South Carolina, and the Virginia Coast Reserve (0.41), USA. Tidal range plays a significant role in that a larger tidal range leads to a smaller optimal IR, and that the landward and seaward limits are displaced toward higher ground elevations. In macrotidal regions the submergence depth is larger, which results in enhanced submergence and salinity stress for the entire marsh, causing it to shift toward higher elevations. Tidal range is an important factor influencing the growth pattern of S. alterniflora, but geomorphological factors such as topographic profiles, and the presence of cliffs and tidal creeks must also be taken into account.
Morphodynamics of the Qiantang Estuary, China : controls of river flood events and tidal bores
The importance of seasonal variations in river discharge on the morphological development of estuaries has been recognized in recent years, yet in situ observations about such variations are rare. Here we report a long-term dataset of bathymetry in the middle reach of the Qiantang Estuary, China, characterized by the presence of a large inner bar. Moreover, a hydrographic survey was carried out in the Yanguan reach where one of the largest tidal bores in the world occurs, covering a spring-neap tidal cycle in 2015. Meanwhile, detailed seasonal bathymetric data together with daily river discharges of 2015 were collected. The bed morphology shows strong seasonal and inter-annual variations. During the high flow season, the river flow erodes the bed and transports a large amount of sediments seaward. A good power-law relationship exists between the high river discharge and the channel volume at the upper estuary. Flood tides dominate under usual river flow condition. In particular, the tidal bore during spring and intermediate tides is characterized by large current velocity and high suspended sediment concentration, and transports a large amount of sediment landward. Over a year, a dynamic morphological equilibrium can be maintained. Moreover, the estuary has also been significantly influenced by the large-scale embankment in recent decades, constraining the lateral thalweg migration, bank erosion and point bar deposition, which usually occur in natural sinuous estuaries.
Designing a monitoring system to detect signals to adapt to uncertain climate change
Adaptive plans aim to anticipate uncertain future changes by combining low-regret short-term actions with longterm options to adapt, if necessary. Monitoring and timely detection of relevant changes, and critical transitions or tipping points is crucial to ensure successful and timely implementation and reassessment of the plan. Although efforts have been made to identify signposts to monitor, the question remains how to design a signal monitoring system that detects and anticipates (future) change to support adaptive planning. For example, to support water related infrastructure investments under uncertain climate change. What are good signposts to monitor and how to wisely analyse them to get timely and reliable signals for adaptation? In this paper, we present a framework for designing and using a monitoring plan as part of the Dynamic Adaptive Policy Pathways (DAPP) approach for decision making under uncertainty. We use the following criteria to evaluate signposts and their critical signal values: measurability, timeliness, reliability, convincibility and institutional connectivity. We illustrate the approach based on the signal monitoring system for the adaptive plan developed by the Delta Programme in the Netherlands.
Are water and conflict linked and what actually links them?
The Water, Peace and Security partnership studies the pathways between water and conflict and the intervening factors. Based on this, it also advices relevant stakeholders to take appropriate action to prevent the deterioration of such situations. It does so by providing a comprehensive package of tools and knowledge that allow for global level analyses of potential water-related conflict hotspots and in-depth local analyses of those, for raising awareness among policy makers on required actions and for advice on which options are available to come to agreed action that can address both the natural and the socio-political aspects of the threat and thus ensure security, peace and sustainable development.
A multi-scale conceptual model of flood-tide delta morphodynamics in micro-tidal estuaries
Wave and tide induced sediment transport pathways and rates govern the morphological evolution of estuarine systems. An understanding of the morphodynamics of these systems is required to maintain their commercial, biological and recreational value. The morphodynamics of Port Stephens estuary, a micro-tidal estuary located on a wave dominated southeast coast of Australia were investigated using bathymetric surveys and current velocity data from several locations over the estuary. This provided detailed insight into the rates and direction of movement for the main sedimentary features of the system, and how these features interact with the processes that drive their evolution. We used these findings to develop a conceptual model for estuarine morphodynamics that accounts for fair weather and storm conditions. Our model explains how sediment eroded from the estuarine beaches is trapped by the adjacent flood-tide delta. The model is applicable to fetch-limited estuaries that do not have offshore sources of sediment, where the tidal currents are weak in relation to the incident ocean waves, and that have a wide, stable entrance through which ocean waves can propagate into the estuary. The model is multi-scale in that it encapsulates both short-term and local process, and large scale evolution of an estuary; therefore, it represents a tool that may be used in developing sustainable estuary management strategies.
Joint assimilation of soil moisture retrieved from multiple passive microwave frequencies increases robustness of soil moisture state estimation