Abstract
Critical water infrastructure is designed to satisfy performance criteria and also withstand natural disasters such as extreme flood scenarios. Safety in this regard has improved drastically over the last century, yet hundreds of casualties occur each year at hydraulic structures from public interactions that include all types of routine social behaviors and recreational activities. For example, in the UK and US such drownings in one year have resulted in as many casualties as deaths due to dam failures in the last 200 years. Herein we explore UK and US official and crowdsourced data to expose a risk perception gap and a neglected class of infrastructure risk. At hydraulic structures, fatal activities across all human ages ranged from accidental to intentional interactions. Examples include walking along a scenic canal, visiting a park, or more intrusive behaviors such as fishing from a dam, canoeing, or sliding down a spillway. Some new activities may be inspired by social media. Contrary to common expectations, the routine interactions with hidden risks are weighty contributors to fatalities and data indicates that alcohol did not play a significant role in these accidents (< 13.5%, UK). Furthermore, only 15% of drownings occurred during swimming activities (UK). Also, public safety measures were generally found to be non-existent or inadequate (US), despite repeated injuries or fatalities at certain structures. Many of these public safety hazards would be readily solved at the design stage, but retrofits that consider local social behaviors can be viable for both newer and legacy infrastructure. Although some risk reduction efforts, including awareness campaigns, are underway for US low-head dams, most other hazards remain invisible, —with walking/running by waterways amounting to 37% of these casualties (UK)—; which contrasts with the complete lack of risk perception by the general population. For these water risks –concealed in plain sight –, several generally applicable solution strategies are proposed herein, hierarchical to their effectiveness and involving interdisciplinary engineering, operation, and governance.