Concerning Swash On Steep Beaches

This investigation focuses on the prediction of sediment transport and beach evolution in coarse-grained beaches. This includes observed morphological changes on both gravel and mixed beaches from experimental investigations at the Large Wave Flume (GWK) in Hanover. Germany. The recorded measurements show that the majority of morphology change took place adjacent to the zone of wave-breaking, close to the shoreline in both cases. Based on these observations, the discussions are carried out with psirticular regard to the observed tendency for onshore transport axid profile steepening in the swash zone. The aim is to identify the cross-shore hydrodynamics and sediment transport mechanisms involved, to advance understanding of this type of beach and to improve our qucintitative capabilities for predicting shoreline and morphological changes in this zone. With this in mind, this thesis includes a discussion of the physical processes related to swash hydrodynamics and sediment transport. It also introduces the description of the mathematical framework used to study wave hydrodynamics in the swash zone. Emphasis is given to the Boussinesq equations which have been found to be a suitable approach. For these equations an evaluation of the two available shoreline boundary conditions is carried out and it is shown that the moving shoreline accurately reproduces the velocity field in the swash zone. The profile evolution investigation is carried out evaluating the transport rates from a bed-load sediment transport formulation coupled with velocities calculated from a set of Boussinesq equations [Lynett et al 2002). Then the equation for conservation of sediment is solved to estimate the morphological changes as proposed by (Rakha et al 1997). It is shown that such an approach is useful to investigate the processes that control this evolution. A discussion on the influence of bottom friction on the predicted profiles is presented. Numerical results in both beaches show that the use of a higher friction factor f during uprush improves the simulations of morphological changes. However, the variation of friction by itself was not able to reproduce the measured profiles. A plausible reason to explain this is that further mechanisms other than friction play an important role in the overall response of coarsegrained beaches. For both beaches it is established that, if the efficiency factor (C) in the sediment transport equation and bottom friction are kept the same in the uprush and backwash, accurate representation of profile evolution is not possible. Indeed, the features of the predicted profiles are reversed. When the C parsimeter is set larger during the uprush than during the backwash, the predicted profiles are closer to the observations. Differences between the predicted profiles from setting non-identical C-values and friction factors for the swash phase, are believed to be linked to both the infiltration effects on the flow above the beachface, the bore collapse picking up sediment from the bed, and the accelerated flow in the uprush. The discussion is made with reference to main physical processes acting over the beachface for both the mixed and gravel beach

Binational reflections on pathways to groundwater security in the Mexico-United States borderlands

Shared groundwater resources between Mexico and the United States are facing unprecedented stressors. We reflect on how to improve water security for groundwater systems in the border region. Our reflection begins with the state of groundwater knowledge, and the challenges groundwater resources face from a physical, societal and institutional perspective. We conclude that the extent of ongoing cooperation frameworks, joint and remaining research efforts, from which alternative strategies can emerge, still need to be developed. The way forward offers a variety of cooperation models as the future offers rather complex, shared and multidisciplinary water challenges to the Mexico–US borderlands

Runup uncertainty on planar beaches

Parameterization of wave runup is of paramount importance for an assessment of coastal hazards. Parametric models employ wave (e.g., H-s and L-p) and beach (i.e., beta) parameters to estimate extreme runup (e.g., R-2%). Thus, recent studies have been devoted to improving such parameterizations by including additional information regarding wave forcing or beach morphology features. However, the effects of intra-wave dynamics, related to the random nature of the wave transformation process, on runup statistics have not been incorporated. This work employs a phase- and depth- resolving model, based on the Reynolds-averaged Navier-Stokes equations, to investigate different sources of variability associated with runup on planar beaches. The numerical model is validated with laboratory runup data. Subsequently, the role of both aleatory uncertainty and other known sources of runup variability (i.e., frequency spreading and bed roughness) is investigated. Model results show that aleatory uncertainty can be more important than the contributions from other sources of variability such as the bed roughness and frequency spreading. Ensemble results are employed to develop a new parametric model which uses the Hunt (J Waterw Port Coastal Ocean Eng 85:123-152, 1959) scaling parameter beta (HsLp)(1/2)

Large scale experiments on gravel and mixed beaches: Experimental procedure, data documentation and initial results

This paper provides information on the experimental set-up, data collection methods and results to date for the project Large scale modelling of coarse grained beaches, undertaken at the Large Wave Channel (GWK) of FZK in Hannover by an international group of researchers in Spring 2002. The main objective of the experiments was to provide full scale measurements of cross-shore processes on gravel and mixed beaches for the verification and further development of cross-shore numerical models of gravel and mixed sediment beaches. Identical random and regular wave tests were undertaken for a gravel beach and a mixed sand/gravel beach set up in the flume. Measurements included profile development, water surface elevation along the flume, internal pressures in the swash zone, piezometric head levels within the beach, run-up, flow velocities in the surf-zone and sediment size distributions. The purpose of the paper is to present to the scientific community the experimental procedure, a summary of the data collected, some initial results, as well as a brief outline of the on-going research being carried out with the data by different research groups. The experimental data is available to all the scientific community following submission of a statement of objectives, specification of data requirements and an agreement to abide with the GWK and EU protocols. (C) 2005 Elsevier B.V. All rights reserved

Binational reflections on pathways to groundwater security in the Mexico-United States borderlands

Shared groundwater resources between Mexico and the United States are facing unprecedented stressors. We reflect on how to improve water security for groundwater systems in the border region. Our reflection begins with the state of groundwater knowledge, and the challenges groundwater resources face from a physical, societal and institutional perspective. We conclude that the extent of ongoing cooperation frameworks, joint and remaining research efforts, from which alternative strategies can emerge, still need to be developed. The way forward offers a variety of cooperation models as the future offers rather complex, shared and multidisciplinary water challenges to the Mexico–US borderlands

Panta Rhei 2013–2015:global perspectives on hydrology, society and change

In 2013, the International Association of Hydrological Sciences (IAHS) launched the hydrological decade 2013–2022 with the theme “Panta Rhei: Change in Hydrology and Society”. The decade recognizes the urgency of hydrological research to understand and predict the interactions of society and water, to support sustainable water resource use under changing climatic and environmental conditions. This paper reports on the first Panta Rhei biennium 2013–2015, providing a comprehensive resource that describes the scope and direction of Panta Rhei. We bring together the knowledge of all the Panta Rhei working groups, to summarize the most pressing research questions and how the hydrological community is progressing towards those goals. We draw out interconnections between different strands of research, and reflect on the need to take a global view on hydrology in the current era of human impacts and environmental change. Finally, we look back to the six driving science questions identified at the outset of Panta Rhei, to quantify progress towards those aims