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A framework for assessing information quality in asset management of flood defences
For asset management of flood defences a pivotal aspect is the quality and accessibility of available data and information. In the management of flood defences in The Netherlands, safety assessments are conducted every twelve years. To assure the quality and consistency of these safety assessments, flood defence engineers have to make use of a comprehensive toolbox and a set of guidelines (WBI 2017). The safety assessment is one of the main starting points for the different asset management processes such as day-to-day maintenance and reinforcement/reconstruction. However, there is no clear method available to assess whether the underlying information is sufficient as a basis for decision making. In this study a framework has been developed that consists of methods for an assessment of the quality of information, an assessment of the use and accessibility of information, and a rational framework for assessing the costs and benefits of obtaining additional information. Whereas many frameworks for information management start from the information itself, here the starting point is the extent to which the behavior of a flood defence is understood, in relation to the decision or management process considered. The applicability of the framework is illustrated using various cases and has been tested in multiple workshops with experts in the field.
Sediment budget analysis of the Guayas River using a process-based model
The Equatorial Daule and Babahoyo rivers meet and combine into the tidal Guayas River, which flows into the largest estuary on the Pacific coast of South America. The city of Guayaquil, located along the Guayas, is the main port of Ecuador but, at the same time, the planet's fourth most vulnerable city to future flooding due to climate change. Fluvial sedimentation, which has increased in the recent years, is seen as one of the factors contributing to the risk of flooding. The planning and design of effective mitigation measures requires a good understanding of the causes which have led to the current hazards. In this study, the process-based Delft3D FM model was used in order to explain the dominant processes in the river and the effects that past interventions along the river and its estuary have had in the overall sediment budget. Additionally, a simulation including sea level rise was used in order to understand the possible future impact of climate change on the sediment budget. Results indicate that the increased import of marine sediment is the result of the recent increase in tidal asymmetry due to land reclamation and a decrease of episodic flushing by river floods due to upstream dam construction. This is in contrast with the local perception of the problem, which ascribes sedimentation to deforestation in the upper catchment. Only the deposition of silt and clay in connected stagnant water bodies could perhaps be ascribed to upstream deforestation.
Risk based inspection of flood defence dams : an application to grass revetments
In The Netherlands, inspection and maintenance are essential for maintaining stringent flood protection standards. Flood defences are assessed every 12 years to ensure they meet their risk-based safety standards, which are given as legally-binding maximum failure probabilities. Between assessments, flood defence managers are subject to risk-maintenance requirements: they must ensure that the failure probability of the defence does not increase in excess of its safety standard. However, there is no prescribed methodology to meet this requirement. In the study presented here, we developed a method which enables flood defence managers to derive inspection strategies using visual inspection data that will allow them to meet their risk-maintenance requirements. We applied the method to the assessment of grass revetments on the outer slope of the Oesterdam, one of the dams of the Dutch Delta Works. The application illustrates how – using visual inspection data,degradation information, and a failure mechanism model – inspection intervals can be derived that will ensure the risk-maintenance requirements are met.
Real time dam stability forecasting
The goal of DAMSAFE is to contribute to enhancing dam safety and water management in India. Innovative tools help in forecasting reservoir inflow and outflow, thus increasing reservoir performance and more controlled release of water in the environment. They allow assessment of the dam condition resulting in optimization of Operation and Maintenance (O&M), while rapid and risk based assessment of dam safety provides information for emergency response. Different technologies, that have been developed and proven elsewhere, provide high quality and reliable information to the end-user. They are implemented in an integrated manner in DAMSAFE.
Life cycle analysis and assessment in civil engineering : towards an integrated vision : proceedings of the Sixth International Symposium on Life-Cycle Civil Engineering - IALCCE 2018 (28-31 October 2018, Ghent, Belgium)
River-regulating at Bajibo (Nigeria) by means of small-scale model-investigation including remote-controlled craft
Validation of flood risk models : current practice and possible improvements
Although often neglected, model validation is a key topic in flood risk analysis, as flood risk estimates are used to underpin large investments and important decisions. In this paper, we discuss the state of the art of flood risk model validation, using as input the discussion among more than 50 experts at two scientific workshop events. The events aimed at identifying policy and research recommendations towards promoting more common practice of validation, and an improvement of flood risk model reliability. We pay specific attention to different components of the risk modelling chain (i.e. flood hazard, defence failure, and flood damage analysis) as well as to their role in risk estimates, to highlight specificities and commonalities with respect to implemented techniques and research needs. The main conclusions from this analysis can be summarised as the need of higher quality data to perform validation and of benchmark solutions to be followed in different contexts, along with a greater involvement of end-users in the application on flood risk model validation.
Morphodynamic feedback loops control stable fringing flats
We apply a 2‐D horizontal process based model (Delft3D) to study the feedback mechanisms that control the long‐term evolution of a fringing intertidal flat in the Western Scheldt Estuary. The hydrodynamic model is validated using a comparison with measurements on the intertidal flat and the sediment transport module is calibrated against long‐term morphology data. First, the processes that lead to net sediment exchange between channel and flat are studied. Then, long‐term simulations are performed and the dependency of sediment fluxes on the tidal flat bathymetry, and the corresponding morphodynamic feedback mechanisms are explained. In the long run, relatively stable states can be approached, which are shown to be typical for wave‐dominated fringing mudflats. The system behavior can be explained by the typical feedback mechanisms between the intertidal bathymetry and the hydrodynamic forces on the flat. In the subtidal domain, the impact of small (5‐10cm) wind waves increases with a rising elevation due to decreasing water depths. In the intertidal domain, the wave impact increases with increasing cross‐sectional slope due to wave shoaling. These relationships result in negative (stabilizing) morphodynamic feedback loops. The tidal current velocities and tide‐induced bed shear stresses, on the other hand, are largely determined by the typical horizontal geometry. A stabilizing feedback loop fails, so that there is no trend towards an equilibrium state in the absence of wind waves.
Notitie watervraag sectoren drinkwater, industrie en energie
In deze notitie worden mogelijke toekomstige wateronttrekkingen in beeld gebracht voor de sectoren drinkwater (en proceswater), industrie en energieopwekking vanuit de ontwikkelingen welke geschetst worden binnen de vier deltascenario’s, teneinde te komen tot consistente en onderscheidende ontwikkelingsscenario’s voor de sectoren. Er wordt per sector een kwantitatieve, verhoudingsgewijze inschatting gemaakt van de wateronttrekking in de jaren 2050 en 2100, ten opzichte van de huidige situatie. Voor de vier deltascenario’s STOOM, WARM, DRUK en RUST.
Effects of different precipitation inputs on streamflow simulation in the Irrawaddy River Basin, Myanmar
Precipitation is the most important input variable to numerically simulate the hydrological responses of a river basin. Nowadays, a number of precipitation data products with different spatial and temporal resolutions are available. However, the accuracy of these products may vary greatly and the variations may themselves differ in different river basins. Such differences have direct implications on the use of these datasets in hydrological modelling. Here, using a hydrological model, we investigated the effects of four precipitation datasets (in-situ gauge precipitation with and without interpolation, PERSIANN-CDR, and CHIRPS) on streamflow simulations in the Irrawaddy Basin in Myanmar. We identified considerable differences in streamflow simulation with the use of different precipitation inputs. The four datasets showed varied annual and seasonal precipitation values over the basin. Although the gauge density within the study area is very low, streamflow simulations forced with interpolated gauge data outperformed the models forced with other datasets. However, simulations forced with CHIRPS and PERSIANN-CDR also showed good results in most cases in terms of Nash Efficiency and R2, but mostly with high biases. In calibration, the four precipitation inputs resulted in varied best-fitted parameter values and ranges. All the above observations indicate that the selection of suitable precipitation input(s) is necessary for an accurate investigation of the hydrological responses of any given basin.