Dionysius C.M. Augustijn

Analytical solution of the depth-averaged flow velocity in case of submerged rigid cylindrical vegetation

A new model for the depth-averaged velocity for flow in presence of submerged vegetation is developed. The model is based on a two-layer approach, where flow above and through the vegetation layer is described separately. Vegetation is treated as a homogeneous field of identical cylindrical stems, and the flow field is considered stationary and uniform. It is demonstrated that scaling considerations of the bulk flow field can be used to avoid complications associated with smaller scale flow processes and that still the behavior of depth-averaged flow over vegetation is described accurately. The derived scaling expression of the average flow field is simple in form, it follows fundamental laws of fluid flow, and it shows very good agreement with laboratory flume experiments. The new model can be used for quick evaluation of a river’s hydraulic response in cases where vegetated floodplains are inundated.

Simulating solute transport in an aggregated soil with the dual-porosity model: measured and optimized parameter values

The capability of the first-order, dual-porosity model, which explicitly accounts for non-ideal transport caused by the presence of ‘immobile’ water, to predict the non-ideal transport of non-sorbing solute in a constructed aggregated soil has been investigated. Miscible-displacement experiments performed with a well-characterized aggregated soil and a non-reactive tracer (pentafluorobenzoate) served as the source of the data. Values for the input parameters associated with physical non-equilibrium were determined independently and compared with values obtained by curve fitting of the experimental measurements. The calculated and optimized values compared well, suggesting that the non-equilibrium parameters represent actual physical phenomena

Nonaqueous Phase Liquid Dissolution and Soil Organic Matter Sorption in Porous Media: Review of System Similarities

We examine similarities in constraints to mass transfer of hydrophobic organic compounds (HOCs) between the aqueous and various organic phases in porous media at the grain scale. Published research and data are reviewed regarding equilibrium coefficients and first-order rate constants for mass transfer of HOCs between water and natural organic matter present in various geosorbents (e.g., soils, sediments, and aquifer solids), and several oils (petroleum products, decane, and coal tar). We propose how these equilibrium and mass-transfer coefficients can be estimated by methods common to all organic phases. Equilibrium coefficients can be reliably estimated using Raoults law. First-order rate constants obtained from extensive literature data appear to be dependent on aqueous-phase diffusion and duration of exposure (or contact). The aqueous diffusion domain may be either an interfacial film (for low viscosity oil ganglia) or a retarded immobile water zone (for geosorbents).

Adapting multireservoir operation to shifting patterns of water supply and demand

The aim of this study is to determine whether dam reoperation (the adjustment of reservoir operating rules) is an effective adaptation strategy to reduce the potential impacts of climate change and regional socio-economic developments. The Xinanjiang-Fuchunjiang reservoir cascade, located in Hangzhou Region (China), is selected as case study. We use a scenario-based approach to explore the effects of various likely degrees of water stress for the future period between 2011 and 2040, which are compared to the control period from 1971 to 2000. The scenario impacts are simulated with the WEAP water allocation model, which is interlinked with the NSGA-II metaheuristic algorithm in order to derive optimal operating rules adapted to each scenario. Reservoir performance is measured with the Shortage Index (SI) and Mean Annual Energy Production (MAEP). For the investigated scenarios, adapted operating rules on average reduce the SI with 84 % and increase the MAEP with 6.4 % (compared to the projected future performance of conventional operation). Based on the optimization results, we conclude that for the studied case dam reoperation is an effective adaptation strategy to reduce the impact of changing patterns of water supply and demand, even though it is insufficient to completely restore system performance to that of the control period.

Evaluation of Policy Transfer Interventions: Lessons from a Dutch-Romanian Planning Project

The transfer of environmental knowledge from one country to another is a widespread practice. This paper presents an evaluation framework to assess the effectiveness of projects that involve such a transfer. It focuses on project-based interventions that are supported by actors of the transferring country. The developed framework is based on the recognition that policy transfer interventions are multi-actor processes and are, therefore, best understood as processes of social interaction. Whether such processes contribute to goal achievement depends on the engagement of users in the process. We further argue that the realization of ultimate outcomes can be estimated or explained on the basis of changes in the characteristics of actors involved. The framework is applied to a Dutch-funded project on flood risk planning in Romania. The ultimate goal of this intervention was to contribute to the solving of water-related problems in Romania and to generate follow-up projects for the Dutch water sector. Central to the project was the active involvement of regional stakeholders in the development of regional spatial plans. Application of the framework shows that the case study is unlikely to contribute to the realization of the desired ultimate outcomes. Process explanations include poor institutional embedding, limited diffusion of project results and a lack of adaptive management. The active involvement of local and regional stakeholders created a shared motivation and knowledge base. However, the project got stuck due to a lack of resources as actors with decision-making power were not involved and ignored the project results.

Estimating mass transfer of polyaromatic hydrocarbons from coal tar-contaminated soil

Many industrial waste disposal/spill sites are characterized by the presence of multicomponent nonaqueous phase liquids (NAPLs) such as gasoline, diesel fuel, oils, and coal tar. The manufacture of gas from coal and oil from the late 1800s to the early 1950s left several manufactured-gas plant (MGP) sites contaminated with coal-tar wastes. These wastes were commonly left on-site in pits and containers, placed in nearby ponds or lagoons, or taken to off-site areas for land disposal (EPRI 1992; Lee et al. 1992b; Luthy et al. 1994). Constituents of particular interest in coal tar include several polyaromatic hydrocarbons (PAHs) currently on the EPA’s priority pollutants list. The threat of the continued release of these organic chemicals to groundwater is resulting in the removal of pure coal tar sources. Given source removal, focus turns to the large amounts of soil that have been contaminated by direct contact with a NAPL or through years of contact with a contaminated aqueous phase.

Quantifying biomass production for assessing ecosystem services of riverine landscapes

Society is increasingly in need of renewable resources to replace fossil fuels and to prevent resource depletion. River-floodplain systems are known to provide important societal functions and ecosystem services to mankind, such as production of vegetative biomass. In order to determine the potential of harvesting vegetative riparian biomass, the capacity of river systems to produce such biomass needs to be determined. We developed a method for quantifying the spatiotemporal development of annual biomass production in river floodplains. Vegetation specific growth rates were linked to a landscape classification system (i.e., the Ecotope System for National Waterways). Biomass production was calculated for floodplains along the three Rhine River distributaries (i.e., the rivers Waal, Nederrijn-Lek and IJssel) over a 15year period (1997-2012). During this period several large scale river management measures were undertaken to reduce flood risks and improve the spatial quality of the Rhine River as part of the Room for the River program. Biomass production decreased by 12%-16% from 1997 to 2012 along the three distributaries, which may be a side effect of flood mitigation. Almost 90% of the biomass produced was non-woody (e.g., grass/hay, reed, crops), which decreased along all three river distributaries due to the abandonment of production grasslands and the physical reconstruction of floodplains (e.g., creation of side channels). Woody vegetation, however, showed a slight increase during the 15year period likely owing to vegetation succession from shrubs to softwood forest.

Coping with Uncertainty in River Management: Challenges and Ways Forward

Coping with uncertainties is inherent to river management planning and policymaking. Yet, policymakers often perceive uncertainty as a complicating factor. We examine the challenges faced by policymakers when coping with uncertainties and provide an action perspective on how to best cope with these challenges to inform the policy debate. Integrating social and natural scientist’s perspectives on uncertainties and learning theories, we present a holistic, management perspective for coping with uncertainty. Based on a literature review about uncertainty concepts, strategies and learning, we identify three challenges in current river management: balancing social and technical uncertainties, being conservative and avoiding to end up a lock-in situation. We then provide a step-wise strategy and concrete actions for policymakers, which are illustrated with several examples. We conclude that coping with uncertainty may require paradigm shifts that can only be achieved through organisational learning. This, we claim, requires reflection, learning and flexibility of policymakers and their organisation.

Suitable landscape classification systems for quantifying spatiotemporal development of riverine ecosystem services

River systems provide numerous ecosystem services that contribute to human well-being. Biophysical quantification of spatiotemporal development of ecosystem services is useful for environmental impact assessments or scenario analyses of river management and could be done by linking biophysical indicators of relevant ecosystem services to landscape classifications that allow analyses of natural and management-induced changes in riverscape characteristics. We analyzed 126 case studies in which landscape classification systems (LCSs) were applied over the period 1989–2014. LCSs were mostly applied at regional (subnational) scales and linked to ecosystem services in 46 case studies. Ecosystem services were linked to landscape patches based on quantitative (monetary or biophysical) or semiquantitative approaches. Only 6 case studies linked ecosystem services to river systems. The number of ecosystem services quantified by biophysical indicators and linked to landscape classes also was limited. Moreover, the spatiotemporal development of these indicators in relation to landscape changes is poorly elaborated. Six selected LCSs were considered suitable for application to river systems and biophysical quantification of spatiotemporal development of ecosystem services (e.g., Coordination of Information on the Environment [CORINE] Land Cover, River Ecotope Classification). Future research should be directed to developing sound indicators for quantification of river ecosystem services and analyzing how these services develop spatiotemporally in relation to natural and anthropogenic changes of the riverscape.

Modelling the LA River: threats and opportunities for the Los Angeles River, USA

i ABSTRACT In the early 1900’s the Los Angeles River in the Los Angeles County, California, USA was an uncontrolled, meandering river, which provided valuable resources (fresh water, irrigation) for the inhabitants. After some devastating floods in the period 1914 – 1938 the Congress and the U.S. Army Corps of Engineers (USACE) decided to change the river into a concrete channel. This channel, which was completed by 1960, has increased the safety of the city by prevented for big floods, but nowadays it causes other problems. Due to the huge urbanization of the city the river became literally and figuratively isolated from people and communities and this is increasingly considered as unwanted and a missed opportunity to make the inhabitants of Los Angeles familiar with its river. Another problem is that due to the high flow velocities as a result of the low friction of the concrete and the steep character of the river (an average slope of 0.29 percent), the concrete washes away at some places, which decreases the safety of the city. Finally, due to the unsystematic channelization of the river (because it happened over a period of many decades), the flood protection levels along its reaches vary considerably. At some places along the river the flood probability seems to be approximately once in 10 years, which is a very low protection level. In 1991 the first plans to revitalize the LA River arose, which finally resulted in a Master Plan published in 2007 by the City of Los Angeles. An Integrated Feasibility Study was published by the USACE in 2013, in which different alternatives (sets of measures) were reviewed, using 1Dmodel HEC-RAS, in which setting up a 2D-model was recommended. In this study a 2D-model of the LA River is set up which is used to investigate flood probabilities in the current situation. After investigating the flood probabilities in the current or reference situation some scenarios with different measures to reduce flood risks along the river are implemented in the model and their consequences are assessed. Using the model and the measures an analysis of changes in flood safety is carried out. The data series of the precipitation in the catchment area of the LA River and of the discharge in the river are analyzed as input for the model and as a check for the model results. Also the relation between the precipitation and the discharge is investigated to be used in the calculations of the scenario with the climate change. The precipitation series and the discharge series are related to each other according to the cross-correlation analysis. However, it is hard to determine a quantitative and accurate relation between the precipitation and the discharge. With the data series of the discharge three extreme value distributions are determined, namely the Gumbel distribution, the Generalized Extreme Value distribution and the Log-Pearson Type III distribution, to estimate the return times at the different stream gauging stations along the river in the current situation and in the different scenarios. It turned out that the extreme value distributions have a high level of uncertainty, due to the limited availability of data, which is reflected in large differences between the distribution. The Generalized Extreme Value distribution is chosen to determine the return times for the current situation and the scenarios based on the R2 and RMSE values of the distributions. To set up the 2D-model the module Delft3D-FLOW of the suite Delft3D, developed by Deltares, is used. This module is a hydrodynamic simulation program which is used to calculate non-steady flow phenomena on a curvilinear, boundary fitted grid. The grid includes the river itself from the Sepulveda Dam to the ocean, as well as the floodplains and some areas in which measures are planned. The bathymetry is obtained from a Digital Elevation Map, obtained by use of LIDAR, and is corrected at some locations with the cross sections used in the 1D-model HEC-RAS of the USACE. The friction coefficients (roughness) are estimated with help of personal experience, Google Earth and information of the USACE. The boundary conditions are the downstream boundary, set by harmonic constituents, the upper boundary condition at the Sepulveda Dam, set