Deltas undEr gLobal impacT of chAnge – DELTA

DELTA Project Description

Project Background
Deltas are dynamic systems driven by constantly changing interactions between land-based fluvial and ocean processes. These flat agricultural lands, accounting for less than 1% of Earth’s land, are vital for the food security of more than half a billion of people. The relative sea level rise (RSLR) and extreme sea levels (ESL) combined with a rapidly growing population and an increasing impact of human activities, threaten the delta communities. In this context and despite the importance of the RSLR-ESL interactions in the delta regions, and particularly in the tropical regions, only a handful of studies has been conducted on this subject. The threat of increasing coastal flood risk emerges as a probable consequence of climate change. Yet, to date comprehensive projections of RSLR-ESL, that include mean sea level, vertical land motions, tides, waves, and storm surges do not exist.

Problem Statement
The classical probabilistic methods, applied, for example, for designing coastal defenses (concepts of return level and return period), assume the stationarity of historic storm statistics, in the sense that their statistical properties do not change with time. However, many studies have shown that the effect of low-frequency climatic variability, climate change and human interventions, cause non-stationarity. If the data have non-stationary variance, there can be more extreme events than predicted by theory based on the stationary assumption.
Moreover, coastal inundation results not only from nonlinear interactions of oceanographic processes, but also from hydrological, and meteorological events, and land vertical motions. This “compound” depends upon the nature and number of physical processes, the range of spatial and temporal scales and the strength of dependence between these processes. We must investigate how to represent and model these compound events.
To address a complex real-world problems associated with the RSLR-ESL coastal inundations, we need to employ together data and techniques issued from both physical and social sciences, in order to propose an integrative applied research focusing on the social vulnerability induced by the RSLR-ESL events in delta regions.

Scientific objectives
1.Adapting the statistical framework of ESL events as a time-varying analysis to the specific case of coastal deltaic inundation.
2.Adapting the innovative statistical framework for predictions of RSLR-ESL events through time-varying and multi-dimensional analysis of coastal deltaic inundation as a compound event.
3.Advancing practical applications of the RSLS-ESL analysis to improve estimates of social vulnerability in deltaic regions.

Strategy & Approach
•Interdisciplinary team: social and physical sciences.
•Training area: Mississippi Delta (US)
•Application: Ganges-Brahmaputra (Bangladesh) and Irrawaddy (Myanmar) deltas.
•Implementing and comparing statistical (Bayesian Networks) and physics-based models (SCHISM) to determine relationships between driving forces, geological constraints, and coastal responses to make probabilistic predictions of deltaic coastal inundations under the future sea level rise scenarios.
•Employing together data and techniques issued from both physical and social sciences, in order to propose an integrative applied research focusing on different aspects of social vulnerability induced by the RSLR-ESL events in delta regions.
•Exploiting fully the potential of the Earth Observing data.

Expected Project Benefits
•Inundation hazard maps will be designed to indicate the probability and uncertainties of flooding over delta space.
•Specifying the sites where and how many people are living at risk of the RSLR-ESL inundations along the coast of the Ganges-Brahmaputra and the Irrawaddy deltas.
•These flooding scenarios, plausible and scientifically credible under future conditions, would serve as a critical decision-making tool for policy makers.