Assessing Multi-Hazard Vulnerability and Dynamic Coastal Flood Risk in the Mississippi Delta: The Global Delta Risk Index as a Social-Ecological Systems Approach

Carl Anderson,Michael Hagenlocher,Fabrice Renaud,John Day

doi:10.3390/w13040577

Abstract

The tight coupling of the social-ecological system (SES) of the Mississippi Delta calls for balanced natural hazard vulnerability and risk assessments. Most existing assessments have approached these components in isolation. To address this, we apply the Global Delta Risk Index (GDRI) in the Mississippi Delta at high-resolution census tract level. We assess SES spatial patterns of drought, hurricane-force wind, and coastal flood vulnerability and integrate hazard and exposure data for the assessment of coastal flood risk. Moreover, we compare current coastal flood risk to future risk in 2025 based on the modelled effects of flood depth, exposure, and changes in ecosystem area in the context of ongoing efforts under the 2017 Louisiana Coastal Master Plan. Results show that the Master Plan will lead to decreases in risk scores by 2025, but the tracts that are currently the most vulnerable benefit less from risk reduction efforts. Along with our index output, we discuss the need for further advancements in SES methodology and the potential for catastrophic hazard events beyond the model parameters, such as extreme rainfall events and very strong hurricanes. Assessing SES risk components can lead to more targeted policy recommendations, demonstrated by the need for Master Plan projects to consider their unequal spatial effects on vulnerability and risk reduction.

Highlights

Understanding the risk profiles of river deltas is important given their unique challenges, resulting from a high coupling of social-ecological systems (SES) with diverse populations and environmental characteristics [1,2,3,4]
Only the spatial distribution of low to high vulnerability classes can be compared across hazards or vulnerability types, but the actual numeric scores cannot
For social vulnerability the indicators Percent of population living in poorly-constructed houses (7; Table 1) and Access to shelter places (10, Table 1) are not relevant to drought, while a number of ecosystem vulnerability indicators are not relevant to hurricane force winds (Table 1)

Summary

Introduction

Understanding the risk profiles of river deltas is important given their unique challenges, resulting from a high coupling of social-ecological systems (SES) with diverse populations and environmental characteristics [1,2,3,4]. Wetlands and intact coastal ecosystems support livelihoods but can reduce the impacts of flooding and storm surge by acting as buffers [5,6,7,8,9]. Ecosystem services are themselves threatened by socionatural hazards, those that are climate-sensitive [10]. A reinforcing feedback loop emerges of environmental degradation leading to diminished services and subsequently increased exposure [11]. The variety of hazards relevant to deltas can have cascading impacts [12]. Drought may reduce the health of protective coastal vegetation, increasing coastal flood risk

Methods

Results

Discussion

Conclusion