Environmental impacts and risks of bridges and tunnels across lakes: An overview.

Bridges and tunnels are built across lakes, especially in China, to improve road connectivity for transportation. However, their environmental impacts and risks have not received adequate attention. In this study, the magnitude of bridges and tunnels across 142 lakes in China were investigated. The investigation revealed that 37 bridges and 10 tunnels (a total length of 56.82 km) were built across 26 lakes during 2000-2020. From 2011 to 2020, the construction rate of bridges and tunnels across lakes in China was ∼6 times higher than the average value worldwide. Their environmental impacts and risks on lakes were summarised by analyzing previous publications screened from the Web of Science platform. The environmental impacts and risks during the bridge/tunnel construction period generally include decrease in water exchange, habitat destruction, biological reduction, increase in suspended solids, and water quality pollution. Tunnel construction may also affect the ecological conditions of groundwater due to its disturbances in the underground area. During the bridge/tunnel operation period, environmental impacts and risks were mainly induced by rainfall events and water pollution accidents. The impacts and risks were highly related to the construction location, bridge/tunnel properties, moving vehicles, fixing activities, and atmospheric deposition. Owing to the existing weaknesses in management practices, a framework, aiming to reduce the environmental impacts and risks caused by bridges and tunnels across lakes, was proposed. The framework identified the critical issues and their corresponding management strategies during the bridge/tunnel construction and operation periods and enabled the generation of the best management strategy for each specific period.