Delta Alliance News

JCP Bangladesh-The Netherlands, newsletter April 2020 This newsletter of the Joint Cooperation Programme Bangladesh–The Netherlands is about the Corona virus, the annual meeting & field visit, the Plenary session in ICSD4, progress in 2019, the Bangladesh Meta Model, DWKD2019, the successful H@CKATHON and makes a closure with relevant upcoming events.
Joint Cooperation Programme Bangladesh–The Netherlands, Thursday 9 April 2020
Collective learning by Delta Alliance Wings The Delta Alliance advocates peer learning, referred to as Delta2Delta learning. In the period 18-20 November 2019, a Delta2Delta learning process has been organized between Bangladesh and Egypt. What are the lessons learned? What are conditions for effective Delta2Delta learning?
Delta Alliance Secretary, Monday 30 March 2020
Geophysical Research Letters publication: 'Scale‐Dependent Evanescence of River Dunes During Discharge Extremes' Abstract: During high river discharge extremes, the growth of dunes can reach a maximum beyond which a transition to upper stage plane bed may occur, enhancing the river's conveyance capacity and reducing flood risk. Our predictive ability of this bedform regime shift in rivers is exclusively built upon high Froude number flows dominated by asymmetric dunes with steep downstream‐facing slipfaces that are rare in natural rivers. By using light‐weight polystyrene particles as a substrate in an experimental flume setting, we present striking dune morphodynamic similarity between shallow laboratory flow conditions and deep rivers, preconditioned that both flow and sediment transport parameters are accurately scaled. Our experimental results reveal the first observation of upper stage plane bed in a shallow laboratory flume that is reached for a Froude number well below unity. This work highlights the need to rethink widely used dune scaling relationships, bedform stability diagrams, predictions of flow resistance, and flood risk.
S. Naqshband & A.J.F. Hoitink, in Geophysical Research Letters, Friday 6 March 2020
Journal of Geophysical Research: Earth Surface article: 'Resilience of River Deltas in the Anthropocene' Abstract (partly): At a global scale, delta morphologies are subject to rapid change as a result of direct and indirect effects of human activity. This jeopardizes the ecosystem services of deltas, including protection against flood hazards, facilitation of navigation, and biodiversity. Direct manifestations of delta morphological instability include river bank failure, which may lead to avulsion, persistent channel incision or aggregation, and a change of the sedimentary regime to hyperturbid conditions. Notwithstanding the in-depth knowledge developed over the past decades about those topics, existing understanding is fragmented, and the predictive capacity of morphodynamic models is limited.
Hoitink, A.J.F., Nittrouer, J.A., Passalacqua, P., Shaw, J.B., Langendoen, E.J., Huismans, Y., & van Maren, D.S., in JGR: Earth Surface, Tuesday 3 March 2020
Nature publication: 'Global-scale human impact on delta morphology has led to net land area gain' Abstract (partly): River deltas rank among the most economically and ecologically valuable environments on Earth. Even in the absence of sea-level rise, deltas are increasingly vulnerable to coastal hazards as declining sediment supply and climate change alter their sediment budget, affecting delta morphology and possibly leading to erosion. However, the relationship between deltaic sediment budgets, oceanographic forces of waves and tides, and delta morphology has remained poorly quantified. Here we show how the morphology of about 11,000 coastal deltas worldwide, ranging from small bayhead deltas to mega-deltas, has been affected by river damming and deforestation.
J.H. Nienhuis, A.D. Ashton, D.A. Edmonds, A.J.F. Hoitink, A.J. Kettner, J.C. Rowland & T.E. Törnqvist, in Nature, Wednesday 22 January 2020
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