# First-order assessment of flood vulnerability in the Chignecto Isthmus, Atlantic Canada

## TL;DR

This study assesses flood vulnerability in the Chignecto Isthmus, showing how rising water levels could impact agriculture, infrastructure, and trade.

## Contribution

The paper introduces a first-order flood vulnerability assessment using static modeling and GIS for the Chignecto Isthmus.

## Key findings

- Water levels near the isthmus can reach within 1 meter of dike crests during spring tides.
- Modest water level increases could inundate thousands of hectares of cropland and critical infrastructure.
- Existing dikes provide a diminishing safety margin, requiring proactive adaptation planning.

## Abstract

The Chignecto Isthmus is the sole land connection between Nova Scotia and mainland Canada, supporting national trade, agriculture and transportation. Much of this low-lying corridor is protected by aging dikes that are increasingly vulnerable to compound flooding from tides, storm surges and sea-level rise. This study combines static flood modeling and GIS-based land use classification to evaluate the elevation-based flood exposure of infrastructure and agricultural land. A planar water surface modeling approach validated with differential GPS measurements was applied to a 1-m-resolution digital elevation model. Results indicate that water levels in the adjacent basin can reach within 1 m of the mean dike crest elevation during spring tides. Planar surface modeling scenarios demonstrate that relatively modest increases in water level beyond this threshold could result in inundation, affecting thousands of hectares of cropland and hundreds of hectares of developed land, along with critical transportation infrastructure. This exposure has the potential to disrupt agricultural productivity, rural livelihoods, groundwater quality and interprovincial supply chains across the isthmus. While simplified, this analysis highlights the diminishing safety margin afforded by existing dikes, underscores the need for more detailed scenario-based modeling and reinforces the importance of proactive adaptation planning to safeguard this nationally significant corridor.