Dynamics and Vulnerability of Delta Systems - loicz

Engagement of policy-relevant bodies, such as the Intergovernmental Panel Climate Change
(IPCC), and the Millennium Development Goals and the Millennium Ecosystem Assessment, to
elevate the understanding of this additional element of the global environmental change question
is urgently needed. IPCC so far focused fundamentally on eustatic and steric sea-level rise and a
broader discussion of deltas at risk is just beginning. We envision a policy structure designed to
help establish a legal framework and monitor research, modeling, and management practices. The
structure should be used to strengthen cooperation among jurisdictions and cultures to tackle
problems affecting deltas irrespective of human-imposed borders and boundaries.
4.2 Assessing Natural Delta Dynamics
More and more deltas are moving away from their pre-Anthropocene morphology (Syvitski &
Saito 2007), and few systems can be studied under their natural settings (Ericson et al. 2006).
Arctic delta systems are among the rare examples of systems relatively undisturbed by humans
and they may provide an opportunity to study how rapid changes in climate per se affect the
deltaic system (Overeem & Syvitski 2008, Figure 4.1). Reconstructions of paleo-deltas will help to
recover historical changes so as to understand how deltas function without human interference,
and thus establish the pre-human state of a delta. It remains imperative to understand natural
dynamics of deltas prior to human intervention, just as it was imperative to understand Holocene
climate before the recent Anthropocene.
This fundamental understanding should lead us in the further enhancement of process-based
numerical delta models (Paola 2000, Overeem et al. 2005). We envision that there will be a
merged approach between existing detailed ‘fluid dynamics models’ and more geological
‘stratigraphic’ or ‘morphodynamic’ models.
• How are deltas formed where natural forcing processes are dominant? How are these
processes best modeled? How dynamic are deltas in a natural environment? Does the
dominance of forcing processes change over time?
• What are the basic mass balances of water, nutrients and sediment in specific delta systems?
• Can we resolve sources and pathways of delta food webs at various scales?
• How do upstream processes impact delta form and function? When and where do delta river
channels switch or bifurcate?
• Deltas developed within a relatively stable range of sea level change. What is the dynamic
range of sea-level rates for stability of deltas, based on freshwater and sediment input regimes
and climatic characteristics?
• How are geomorphology and ecology linked? What are ecological consequences of natural
changes in landforms? How do we numerically model this interaction?
• What is the role of delta fringe processes as protective buffers to the inland deltas?
• What is the role of extreme events, e.g. river floods and hurricanes, in creating and shaping
deltas? What is the coherence (or incoherence) between river flood events and ocean storms
and is this systematic and forced by regional climate patterns?
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