Modelling damage due to low flows in the Meuse. Poster.

In this research the damage due to low discharges on the Meuse has been analysed to get a better view on the scope of the low flow problem. The research area consists of the Dutch and the Flemish part of the Meuse upstream of Roermond and the canals fed by it. A model has been developed to assess the total damage and the distribution over different regions and economic sectors in a number of situations. Total damage varies from a few million Euros in a medium dry year to ten times that much in an extreme dry year. Most of the damage occurs in the navigation sector and the power generation sector. Climatological and economical development will increase future damage substantially. On the other hand, much can be gained by applying appropriate management strategies

Improving mesh set-up to increase cross-sectional-area accuracy for water-level prediction

An accurate prediction of river water levels using hydraulic modelling is essential for adequate rivermanagement. 2D models are one of the best choices for simulating river hydraulics as they enable moredetailed and accurate simulations of water levels and flood patterns. The bathymetry in 2D models generallyis described with a continuous mesh covering the main channel and floodplain. The mesh set-upcan affect the simulation results significantly, and selecting a suitable mesh is as crucial as applying anappropriate calibration method. The mesh resolution affects bathymetry discretization, discharge capacity,and, consequently, simulated water levels. A higher resolution leads to more precise results, but onthe other hand high resolution models are time consuming. This study aims to develop a modified meshset-up with the same cross-sectional flow area as the measured cross-section at the highest resolution.The modified mesh is developed using an algorithm which changes the nodes of the mesh vertically fora limited range to determine the mesh with the same flow area as observed, but at a lower resolution.Then, D-Flow-FM software is used to model a hypothetical river for 100 kilometers with one uniformcross-section to exclude the effect of longitudinal variability in cross sections on the results. A constantroughness is considered to exclude the effect of roughness on the results and evaluate the effectof mesh set-up on the discharge capacity and predicted water levels. Moreover, a steady inflow of low,intermediate and high flows is used as upstream boundary condition. For comparison, simulated waterlevels for the high-resolution mesh, the current mesh in the D-Flow-FM model and the modified meshare compared. Differences between water levels simulated with the current mesh and the modified meshare around 3 to 10 centimeters, but the modified mesh and the high-resolution mesh simulate the samewater levels for different types of cross sections and discharge levels

Quantification of uncertainties in a 2D hydraulic model for the Dutch river Rhine using expert opinions

Hydraulic–morphological river models are applied to design and evaluate measures for purposes such as safety against flooding. These numerical models are all based on a deterministic approach. However, the modeling of river processes involves numerous uncertainties. The aim of this study is to identify the sources of uncertainty that induce the largest uncertainties in the model outcomes and quantify this uncertainty using expert opinions. Experts have been selected based on a Pedigree matrix. The selected experts are asked to list and quantify the most important uncertainty sources for two situations: (1) the computation of design water levels (DWL) and (2) the computation of the hydraulic effect of a change in the river bed. The experts stated that the sources of uncertainty are different for the computation of the DWL and effect studies. The experts agreed that for DWL, the upstream discharge and the roughness predictor for the main channel have the largest uncertainty. For effect studies, no clear dominant source could be identified. The quantification of the uncertainty sources showed a significant effect on the predicted water levels under design discharge conditions

Long-term consequences of juvenile vulvar lichen sclerosus:A cohort study of adults with a histologically confirmed diagnosis in childhood or adolescence

INTRODUCTION: Vulvar lichen sclerosus (VLS) occurs in at least one in 900 girls. There is limited knowledge as to what extent the disease persists in adulthood and what the repercussions in adulthood may be. The aim of this study is to evaluate the long-term consequences of VLS diagnosed in childhood or adolescence. MATERIAL AND METHODS: The population of females histologically diagnosed with VLS in childhood or adolescence in the Netherlands between 1991 and 2015 was identified through the national pathology database. Histological specimens were retrieved and re-evaluated. Potential participants for whom the diagnosis was reconfirmed and who are now adults, were then traced and surveyed. Descriptive statistics were calculated and compared with the literature. Main outcome measures are the demographics of the cohort, their scores on standardized quality of life (QoL) and sexuality questionnaires and answers to additional questions regarding patients' experience with the disease. The questionnaires used were the Dermatology Life Quality Index (DLQI), the Skindex-29, the Female Sexual Function Index (FSFI) and the Female Sexual Distress Scale-Revised (FSDS-R). Secondary outcome measures include obstetric history and histological features found in the original tissue specimens. RESULTS: A total of 81 women participated, median age 29.0 years, median follow-up from childhood diagnosis 19.5 years. Both QoL and sexuality were somewhat affected in 51.9% of cases. Less than half (45%) reported having regular check-ups. Forty-five (56%) reported symptoms within the past year; of those with symptoms, 14 (31%) were not under surveillance. Cesarean section rate (14.5%) was comparable to the general population, and there were more high-grade obstetric anal sphincter injuries with vaginal deliveries than expected. Sixteen respondents (20%) were not aware of the childhood diagnosis prior to this study. CONCLUSIONS: Symptoms due to VLS are reported by most adults diagnosed as juveniles. QoL and sexuality are affected and correlate to recent symptoms. VLS as a juvenile does not preclude a vaginal delivery. Women diagnosed with VLS in childhood or adolescence are often lost to follow-up.</p

Apixaban versus no anticoagulation after anticoagulation-associated intracerebral haemorrhage in patients with atrial fibrillation in the Netherlands (APACHE-AF):a randomised, open-label, phase 2 trial

Background In patients with atrial fibrillation who survive an anticoagulation-associated intracerebral haemorrhage, a decision must be made as to whether restarting or permanently avoiding anticoagulation is the best long-term strategy to prevent recurrent stroke and other vascular events. In APACHE-AF, we aimed to estimate the rates of non-fatal stroke or vascular death in such patients when treated with apixaban compared with when anticoagulation was avoided, to inform the design of a larger trial. Methods APACHE-AF was a prospective, randomised, open-label, phase 2 trial with masked endpoint assessment, done at 16 hospitals in the Netherlands. Patients who survived intracerebral haemorrhage while treated with anticoagulation for atrial fibrillation were eligible for inclusion 7-90 days after the haemorrhage. Participants also had a CHA2DS2-VASc score of at least 2 and a score on the modified Rankin scale (mRS) of 4 or less. Participants were randomly assigned (1:1) to receive oral apixaban (5 mg twice daily or a reduced dose of 2.5 mg twice daily) or to avoid anticoagulation (oral antiplatelet agents could be prescribed at the discretion of the treating physician) by a central computerised randomisation system, stratified by the intention to start or withhold antiplatelet therapy in participants randomised to avoiding anticoagulation, and minimised for age and intracerebral haemorrhage location. The primary outcome was a composite of non-fatal stroke or vascular death, whichever came first, during a minimum follow-up of 6 months, analysed using Cox proportional hazards modelling in the intention-to-treat population. APACHE-AF is registered with ClinicalTrials.gov (NCT02565693) and the Netherlands Trial Register (NL4395), and the trial is closed to enrolment at all participating sites. Findings Between Jan 15, 2015, and July 6, 2020, we recruited 101 patients (median age 78 years [IQR 73-83]; 55 [54%] were men and 46 [46%] were women; 100 [99%] were White and one [1%] was Black) a median of 46 days (IQR 21-74) after intracerebral haemorrhage. 50 were assigned to apixaban and 51 to avoid anticoagulation (of whom 26 [51%] started antiplatelet therapy). None were lost to follow-up. Over a median follow-up of 1.9 years (IQR 1.0-3.1; 222 person-years), non-fatal stroke or vascular death occurred in 13 (26%) participants allocated to apixaban (annual event rate 12.6% [95% CI 6.7-21.5]) and in 12 (24%) allocated to avoid anticoagulation (11.9% [95% CI 6.2-20.8]; adjusted hazard ratio 1.05 [95% CI 0.48-2.31]; p=0.90). Serious adverse events that were not outcome events occurred in 29 (58%) of 50 participants assigned to apixaban and 29 (57%) of 51 assigned to avoid anticoagulation. Interpretation Patients with atrial fibrillation who had an intracerebral haemorrhage while taking anticoagulants have a high subsequent annual risk of non-fatal stroke or vascular death, whether allocated to apixaban or to avoid anticoagulation. Our data underline the need for randomised controlled trials large enough to allow identification of subgroups in whom restarting anticoagulation might be either beneficial or hazardous. Copyright (C) 2021 Elsevier Ltd. All rights reserved

Quantification of uncertainty in design water levels due to uncertain bed form roughness in the Dutch river Waal

Hydrodynamic river models are applied to design and evaluate measures for purposes such as safety against flooding. The modelling of river processes involves numerous uncertainties, resulting in uncertain model results. Knowledge of the type and magnitude of these uncertainties is crucial for a meaningful interpretation of the model results. Uncertainty in the hydraulic roughness due to bed forms is one of the main contributors to the uncertainty in the modelled water levels. The aim of this study was to quantify the uncertainty in the bed form roughness under design conditions and quantify the effect on the design water levels in the Dutch river Waal. Five roughness models that predict bed form roughness based on measured bed form and flow characteristics were extrapolated to design conditions. The results show that the 95% confidence interval of the predicted Nikuradse roughness values under design conditions ranges from 0.32 to 1.03 m. This uncertainty was propagated through the two-dimensional hydrodynamic model, WAQUA, by means of a Monte Carlo simulation for an idealized schematization of the Dutch river Waal. The uncertain bed form roughness results in an uncertainty in the design water levels, with a 95% confidence interval of 0.53 m, which is significant for Dutch river management practice. The uncertainty in the bed form roughness was mainly caused by a lack of knowledge about the physical process of bed form evolution that causes roughness. An improved estimation of bed form roughness can significantly reduce the uncertainty in the design water levels

Uncertainty of design water levels due to combined bed form and vegetation roughness in the Dutch river Waal, doi: 10.1111/jfr3.12014

Two-dimensional hydrodynamic models are frequently used for flood protection studies to compute inundation patterns and to estimate potential economic damage. However, the modelling of river processes involves numerous uncertainties. Knowledge of the type and magnitude of uncertainties is crucial for a meaningful interpretation of the model outcomes and its usefulness in decision making. The objective of this study was to quantify the uncertainty in the design water levels due to uncertain bed form and vegetation roughness for the Dutch River Waal. We quantified and combined these sources of uncertainty by means of a Monte Carlo simulation. The results showed that the 95% confidence interval of the design water levels is 0.49m, 0.34m and 0.12m for bed form, vegetation classification and vegetation roughness parameterisation, respectively, and approximately 0.68m for the combined roughness. These uncertainties are significant in view of Dutch river management practic