Global-Scale Assessment of Threatened River Delta Systems: Evaluation of Connections Between the Continental Land Mass and Ocean Through Integrated Remote Sensing and Process Modeling

River systems are today experiencing a transformation that is rapid and pandemic in extent, affected by climate trends and variability plus widespread land cover change, wetland destruction, pollution, and waterworks like dams, irrigation, and interbasin transfers that distort, and often break, the basic character of land-to-ocean linkages. Impacts reverberate strongly into the coastal zone, on which a substantial fraction of the human population lives and depends for critical environmental services. A particularly sensitive part of this zone is the coastal river delta, on which >0.5B people live and which owes its existence to the interplay between water and sediment fluxes defined by upland watershed dynamics, local conditions, and ocean forcings. While problems are well-documented for single river deltas, they collectively point to a worldwide syndrome, an assertion to be formally tested here using remote sensing, modeling, and GIS.

With population growth, development, and the specter of sea level rise and changes in storm and flood surge exposure, river deltas increasingly are a focal point for concerns regarding human vulnerability and sustainable development. The need to understand and forecast the rapidly changing state of these linked geophysical-social systems is the impetus for our proposed study. This proposal aims at the Vulnerability, Impacts, and Adaptation (VIA) element of the LCLUC program ROSES solicitation, with its emphasis on wetlands. Our Science Goal is to analyze how the strength and variability of land-to-ocean links, as defined by reverine sediment fluxes, local anthropogenic activities and ocean processes, produce impacts on coastal delta systems today and into the future.

The supporting Objectives are to: 1) refine and apply a "fingerprinting" system to identify hot spots/cold spots of risk, 2) improve understanding of key delta system response mechanisms to environmental stressors, 3) assess contemporary societal vulnerabilities and 4) forecast future threat.

The proposal extends ongoing work to develop river basin and coastal models and linked Earth system modeling frameworks. Our recent work has yielded several breakthroughs in the science of land-to-ocean coupling, including global dynamic, geospatial flux models and demonstrations of the value of NASA remote sensing assets. Our analysis framework integrates unique global-scale remote sensing data sets of wetland vegetation and dynamics and land surface freeze-thaw state developed under the NASA MEaSUREs program. The proposal takes data sets now under development and extends their domain to address issues of regional and global significance. Principal, value-added outputs from this proposal over our current research are: a synthesis of landmass, coastal wetland, and coastal ocean remote sensing observations, models, and statistical inference techniques a global catalogue of delta systems-at-risk and scenarios of future conditions which can be used in the policy arena.

The proposal articulates upland as well as local coastal impacts of LCLUC on a sensitive coastal wetland system, which serves as home to rapidly growing megacities and rural populations. The work places these impacts into a broader perspective of sea level rise and ocean storm-derived vulnerabilities. The aims of this proposal thus contribute to the overall mission of NASA's Science Mission Directorate and US Climate Change Science Program by improving knowledge on a central global change issue and distinguishing the impact of climate from other drivers. The work supports the Directorate's aim of assessing the capacity of multiple satellite sensors and data sets to monitor change in biogeophysical cycles over both landmass and oceans. The subject of this proposal has important societal implications, and PI/co-PI participation in international science consortia and policy-relevant activities are forwarded as part of this work.