Abstract
A study of floodplain sedimentation on a recently restored floodplain is presented. This study uses a two‐dimensional hydro‐morphodynamic model for predicting flow and suspended‐sediment dynamics in the downstream of Johnson Creek, the East Lents reach, where the bank of the river has been reconfigured to reconnect to a restored floodplain on a 0.26 km2 (26‐ha) site. The simulation scenarios include 10‐, 50‐, 100‐ and 500‐year event‐based deposition modelling of flood events and long‐term modelling using the 64 historical flood events between 1941 and 2014. Simulation results showed that the restored floodplain significantly attenuates the upstream flood peak by up to 25% at the downstream. Results also indicated that approximately 20%–30% of sediment from the upstream is deposited on the East Lents floodplain. Furthermore, deposited sediment over the simulated period (1941–2014) is approximately 0.1% of the basin's flood storage capacity; however, the reduction in the storage does not offset the overall flood resilience impact of the flood basin. The sediment conservation at the East Lents flood basin as predicted by the model reduces the annual sediment loading of the Johnson Creek by 1% at the confluence with Willamette River, providing both improved water quality and flood resilience further downstream.
Highlights
The Pacific Northwest, like many regions of the United States has become increasingly urbanised (Yeakley et al 2014) as a result of growing urban population and socioeconomic development
There is a floodgate in place on west side of the floodplain to release part of the flood storage back to the Johnson creek in a control manner further upstream of the study region, but this release is not included in the model as it is not pertinent to the study
The application of a two-dimensional hydromorphodynamic model to the Johnson Creek, the East Lents reach demonstrates that floodplain restorations can have a pronounced effect on flood and sediment dynamics
Summary
The Pacific Northwest, like many regions of the United States has become increasingly urbanised (Yeakley et al 2014) as a result of growing urban population and socioeconomic development. Urban flood risk is function of hazard, exposure and vulnerability (Ronco et al 2014). These three factors should be addressed and considered when quantifying flood risk. The Federal Emergency Management Agency (FEMA) considers flooding the number one natural hazard in the United States. In the Pacific Northwest of the United States, winter and spring flood risk in rain-snow transient basins are projected to increase in the 21st century (Dalton et al 2013; Salathé et al 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
