Building on piles in floodplains

Last year in the Netherlands 15 locations were allocated along the Rhine branches where – under strong restrictions - it was allowed to build in floodplains. Building in floodplains may lead to a water level rise during floods and moreover, the river bed morphology may be disturbed (erosion/sedimentation). A potential building location on a floodplain of the river IJssel near Deventer (Wilpsche Klei) is used as a fictitious case to investigate these processes

Long term claims on the Dutch river area: handling climate change, safety, navigation and nature

River engineeringFlow management and contro

A gravel-sand bifurcation:a simple model and the stability of the equilibrium states

A river bifurcation, can be found in, for instance, a river delta, in braided or anabranching reaches, and in manmade side channels in restored river reaches. Depending on the partitioning of water and sediment over the bifurcating branches, the bifurcation develops toward (a) a stable state with two downstream branches or (b) a state in which the water discharge in one of the branches continues to increase at the expense of the other branch (Wang et al., 1995). This may lead to excessive deposition in the latter branch that eventually silts up. For navigation, flood safety, and river restoration purposes, it is important to assess and develop tools to predict such long-term behavior of the bifurcation. A first and highly schematized one-dimensional model describing (the development towards) the equilibrium states of two bifurcating branches was developed by Wang et al (1995). The use of a one-dimensional model implies the need for a nodal point relation that describes the partitioning of sediment over the bifurcating branches. Wang et al (1995) introduce a nodal point relation as a function of the partitioning of the water discharge. They simplify their nodal point relation to the following form: s*=q*k , where s* denotes the ratio of the sediment discharges per unit width in the bifurcating branches, q* denotes the ratio of the water discharges per unit width in the bifurcating branches, and k is a constant. The Wang et al. (1995) model is limited to conditions with unisize sediment and application of the Engelund & Hansen (1967) sediment transport relation. They assume the same constant base level for the two bifurcating branches, and constant water and sediment discharges in the upstream channel. A mathematical stability analysis is conducted to predict the stability of the equilibrium states. Depending on the exponent k they find a stable equilibrium state with two downstream branches or a stable state with one branch only (i.e. the other branch has silted up). Here we extend the Wang et al. (1995) model to conditions with gravel and sand and study the stability of the equilibrium states

Evolution of bed form height and length during a discharge wave

This research focusses on modeling the evolution of bed form during a discharge wave for application in operational flood forecasting. The objective of this research was to analyze and predict the bed form evolution during a discharge wave in a flume experiment. We analyzed the data of a flume experiment and show that dune length is determined by development of secondary bed forms during the receding limb of the discharge wave. Secondly, three models were compared to predict the bed form evolution: an equilibrium model, a time-lag model and the physically-based, numerical model of Paarlberg et al. (2010). We show some preliminary results and show that the numerical model seems promising for modeling bed form evolution for operational flood forecasting

Data-Driven Surrogate Models For Flood Defence Failure Estimation : “Jarillon” Of Cali, Colombia Case Study

The city of Cali is the main urban center of the south-western part of Colombia. It is located along the Cauca river, the second largest in the country. At the moment, the embankment located along the left margin that protects the city is designed for a return period of 100 years. In this study is intended to make a probabilistic analysis for dike failure for the present state of this flood defence. The water levels inside the main stream are highly sensitive to the peak discharge of upstream near tributaries which must be included in the analysis. An existent hydrodynamic model can be used for the estimation of the possible water levels but it requires large amounts of input data and is highly time consuming. Simulation of hydrodynamics and geotechnical stability models are quite advanced right now but for reliability studies might not be the most efficient solution. Therefore meta-modeling procedures could be implemented if accurate and sufficient data is available. For this study, different data-driven surrogate models where coupled as a solution for flood defense failure calculation tools. These models where used to estimate the loads and resistance combined effects of the actual flood defense for several different failure mechanisms. Algorithms like ANN and M5P where applied for building the data-driven surrogate models for each levee failure mechanism. Calculation time was reduced sufficiently to make it a feasible solution for this kind of studies. The final models can also be used as design tools if their application ranges is sufficiently understood

Mechanisms for sediment fining in a side channel system

Side channels have been constructed in the Dutch river system to reduce flood risk and to increase the ecological value of the river. Some of these side channels show large aggradation and therefore require regular maintenance. Grain size measurements of the deposited sediment show that the bed of the side channel contains much finer sediment (0.2-0.3 mm) than the bed of the main channel (1-2 mm). This suggest that sorting occurs at the bifurcation of the side channel which likely affects the equilibrium state and the time scale of the side channel development. The objective is to reproduce the morphodynamic development with a 2D numerical model that allows for sorting processes. The dimensions of the system are based on the Waal River in the Netherlands