Hurricane Harvey caused severe wind damages and flooding in Fall, 2017. In fact, the associated flooding can be classified as a 5,000 year event. Associated to the flooding, significant sediment relocation processes occurred. Sediment erosion around submerged structures and foundations, commonly referred to as scour, represents a significant risk to the stability of infrastructures. During Hurricane Harvey, early reconnaissance teams observed significant scour and erosion at bridge piers, river embankments, sheet pile walls, boulder walls, and other infrastructure with submerged foundations. However, safety constraints limited on site investigations while water levels were still elevated. An issue of post-event scour and erosion investigations is the refilling of scour holes. This means that when with receding water levels and flow velocities, sediment transported in suspensions settles and infills the scour holes, often leading to false assessments of the magnitude of erosion during the event. Additionally, the infill is freshly deposited and often weak, potentially providing a false image of stability. This award will support the collection of perishable field data investigating scour and erosion, as well as post-event infill at locations impacted by flooding and storm surge during Hurricane Harvey. The collected data will advance the understanding of scour, erosion, and infill during extreme flooding events, and therefore, contribute directly to the improvement of risk assessment.
The research team will visit sites that experienced severe scour and erosion during Hurricane Harvey, and that were initially investigated by early reconnaissance teams. An integrated geotechnical and geophysical approach will be employed to gather a unique data set of scour and erosion, and the subsequent infilling. Sub-bottom echo sounders (chirp sonar) will profile the submerged sediment stratigraphy, supported by portable free fall penetrometer deployments which will provide geotechnical parameters of the different sediment layers. Side scan sonar and photogrammetry will provide detailed imagery and topography. In-situ erodibility will be tested using a cohesive strength meter. Gravity coring will enable sediment sampling in submerged areas, while push tube sampling will be conducted at emerged banks. Sediment samples will be tested for geotechnical sediment characteristics, and erodibility. The latter tests will be conducted using a Erosion Flume Apparatus. The collected field data will be unique by providing geotechnical information from the native sediments and the infill, and will enable future research and insights into the erosion and infill processes associated to extreme flooding events as during Hurricane Harvey. The data will be made available to the public and other researchers immediately after collection through the Designsafe-CI data repository.