Seismic signature of turbulence during the 2017 Oroville Dam spillway erosion crisis
Knowing the location of large-scale turbulent eddies during catastrophic flooding events improves predictions of erosive scour. The erosion damage to the Oroville Dam flood control spillway in early 2017 is an example of the erosive power of turbulent flow. During this event, a defect in the simp...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-05-01
|
| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/6/351/2018/esurf-6-351-2018.pdf |
| Summary: | Knowing the location of large-scale turbulent eddies during catastrophic
flooding events improves predictions of erosive scour. The erosion damage to
the Oroville Dam flood control spillway in early 2017 is an example of the
erosive power of turbulent flow. During this event, a defect in the simple
concrete channel quickly eroded into a 47 m deep chasm. Erosion by turbulent
flow is difficult to evaluate in real time, but near-channel seismic
monitoring provides a tool to evaluate flow dynamics from a safe distance.
Previous studies have had limited ability to identify source location or the
type of surface wave (i.e., Love or Rayleigh wave) excited by different river
processes. Here we use a single three-component seismometer method
(frequency-dependent polarization analysis) to characterize the dominant
seismic source location and seismic surface waves produced by the Oroville
Dam flood control spillway, using the abrupt change in spillway geometry as a
natural experiment. We find that the scaling exponent between seismic power
and release discharge is greater following damage to the spillway, suggesting
additional sources of turbulent energy dissipation excite more seismic
energy. The mean azimuth in the 5–10 Hz frequency band was used to resolve
the location of spillway damage. Observed polarization attributes deviate
from those expected for a Rayleigh wave, though numerical modeling indicates
these deviations may be explained by propagation up the uneven hillside
topography. Our results suggest frequency-dependent polarization analysis is
a promising approach for locating areas of increased flow turbulence. This
method could be applied to other erosion problems near engineered structures
as well as to understanding energy dissipation, erosion, and channel
morphology development in natural rivers, particularly at high discharges. |
|---|---|
| ISSN: | 2196-6311 2196-632X |