Use of sacrificial embankments to minimize bridge damage from scour during extreme flow events

The leading cause of bridge failure has often been identified as bridge scour, which is generally defined as the erosion or removal of streambed and/or bank material around bridge foundations due to flowing water. These scour critical bridges are particularly vulnerable during extreme flood events, and pose a major risk to human life, transportation infrastructure, and economic sustainability. Retrofitting the thousands of undersized and scour critical bridges to more rigorous standards is prohibitively expensive requiring effective yet economical countermeasures. This research tested the efficacy of using approach embankments as intentional sacrificial “fuses” to protect the bridge integrity and minimize damage during large flow events by allowing the streams to access their natural floodplain and reduce channel velocities. This countermeasure concept was evaluated using the Hydrologic Engineering Center’s River Analysis System models. Steady flow models were developed for three specific bridges on two river reaches. Streamflow return period estimators for both river reaches were developed using Bayesian analysis and available United States Geological Survey stream gauge data to evaluate sacrificial embankments under non-stationary climatic conditions. The use of sacrificial embankments was determined to be a cost-effective scour mitigation strategy for bridges with suboptimal hydraulic capacity and unknown or shallow foundations. Additional benefits of sacrificial embankments include reductions in upstream flood stage and velocity.     

Small unmanned airborne systems to support oil and gas pipeline monitoring and mapping

Oil and gas transmission pipelines require monitoring for maintenance and safety, to prevent equipment failure and accidents. Unmanned aerial vehicles (UAVs) technology is emerging as an opportunity to supplement current monitoring systems. Small UAV technological solutions are flexible and adaptable and with a demonstrated capacity to obtain valuable data at small to medium spatial scales. Systematic surveys of extensive areas are better completed with fixed-wing platforms and automatic flight design, whilst multirotor platforms provide flexibility in shorter and localized inspection missions. The type of sensor carried by an aerial platform determines the sort of data acquired and the obtainable information; sensors also determine the need for specific mechanical designs and the provision of energy on-board required from the system. UAV systems prototyped to monitor pipelines are reviewed in this paper, and a number of monitoring scenarios are proposed and illustrated. Notwithstanding difficulties encountered in the generalization of use for civilian applications, small UAVs have demonstrated, through research and operational cases, the capacity to support the inspection and monitoring of oil and gas pipelines.     

Analysis of growing season carbon and water fluxes of a subalpine wetland in the Canadian Rocky Mountains: Implications of shade on ecosystem water use efficiency

Mountain regions are an important regulator in the global water cycle through their disproportionate water contribution. Often referred to as the “Water Towers of the World”, mountains contribute 40%–60% of the world's annual surface flow. Shade is a common feature in mountains, where complex terrain cycles land surfaces in and out of shadows over daily and seasonal scales, which can impact water use. This study investigated the turbulent water and carbon dioxide (CO₂) fluxes during the snow-free period in a subalpine wetland in the Canadian Rocky Mountains, from 7 June to 10 September 2018. Shading had a significant and substantial effect on water and CO₂ fluxes at our site. When considering data from the entire study period, each hourly increase of shade per day reduced evapotranspiration (ET) and gross primary production (GPP) by 0.42 mm and 0.77 g C m^?2, equivalent to 17% and 15% per day, respectively. However, the variability in shading changed throughout the study, it was stable to start and increased towards the end. Only during the peak growing season, the site experienced days with both stable and increasing shade. During this time, we found that shade, caused by the local complex terrain, reduced ET and potentially increased GPP, likely due to enhanced diffuse radiation. The overall result was greater water use efficiency during periods of increased shading in the peak growing season. These findings suggest that shaded subalpine wetlands can store large volumes of water for late season runoff and are productive through short growing seasons.