Spatiotemporal pattern of successive hydro-hazards and the influence of low-frequency variability modes over Canada

Abstract

Successive hydro-hazards, particularly dry and wet weather whiplash, can severely impact societies and infrastructure undermining the resilience measures developed based on the traditional univariate approaches. Understanding the spatial and temporal characteristics of such lagged compound events is important to improve the efficacy of disaster risk measures (DRMs). This study analyzes the successive dry-wet and wet-dry (SDW/SWD) spells based on the run theory across Canada and proposes a compound magnitude index to identify the corresponding hotspots across 268 watersheds for the historical period of 1963–2012. The frequency, transition time, and magnitude of SDW/SWD events are assessed considering the variable monthly 20th percentile (dry spell) and a fixed 90th percentile (wet spell) of natural streamflow values as thresholds. The potential influence of low-frequency variability modes such as Multivariate El Niño–Southern Oscillation (ENSO) index (MEI) and the North Atlantic Oscillation (NAO) index on the regional hydro-hazards, with a transition time of less than a month, is assessed based on the Bayesian quantile regression approach. Results indicate that the coastal areas, including the west and east coast and the Great Lakes region, are the hotspots for such abrupt transitions. Furthermore, the spatial and temporal characteristics of SDW/SWD events are largely variable and different from those of individual events. The magnitude of these events is influenced by low frequency variability modes particularly at higher quantiles, suggesting that strong phases of MEI and NAO can potentially lead to SDW and SWD events. The findings of this study support the future development of robust DRMs and effective water resource management strategies.