Possible Weakening Processes Imposed on California’s Earthen Levees under Protracted Drought

Abstract:

California is currently suffering from a multiyear extreme drought and the impacts of the drought are anticipated to worsen in a warming climate. The resilience of critical infrastructure under extreme drought conditions is a major concern which has not been well understood. Thus, there is a crucial need to improve our understanding about the potential threats of drought on infrastructure and take subsequent actions in a timely manner to mitigate these threats and adopt our infrastructure for forthcoming extreme events. The need is more pronounced for earthen levees, since their functionality to protect limited water resources and dryland is more critical during drought. A significant amount of California’s levee systems are currently operating under a high risk condition. Protracted drought can further threaten the structural competency of these already at-risk levee systems through several thermo-hydro mechanical weakening processes that undermine their stability. Viable information on the implications of these weakening processes, particularly on California’s earthen levees, is relatively incomplete. This article discusses, from a geotechnical engineering perspective, how California’s protracted drought might threaten the integrity of levee systems through the imposition of several thermo-hydro mechanical weakening processes. Pertinent facts and statistics regarding the drought in California are presented and discussed. Catastrophic levee failures and major damages resulting from drought-induce weakening processes such as shear strength reduction, desiccation cracking, land subsidence and surface erosion, fissuring and soil softening, and soil carbon oxidation are discussed to illustrate the devastating impacts that the California drought might impose on existing earthen levees. This article calls for further research in light of these potential drought-inducing weakening mechanisms to support mitigation strategies for reducing future catastrophic levee failures.