Birch Bay in northwest Washington was the site of coastal flooding during the last storm system.
The flooding was in part the result of the initial low pressure system just off the west side of Vancouver Island. The low created pressure itself caused a sea level rise on the order of 1 foot above the astronomical tide levels. The location of the low off Vancouver Island also created winds that pushed water into the Strait of Juan de Fuca and Salish Sea. The local winds further enhanced the storm surge of tide levels. The local winds also were oriented to develop large waves in a bay that is otherwise rather calm.
The closest tide station with continuous measurements is just south of Birch Bay at Cherry Point. The storm surge at Cherry Point during the storm was 2.5 feet; a high surge for the Salish Sea.
The maximum storm surge coincided with the peak astronomical tide. I suspect that that the storm surge at Birch Bay was even higher due to local geometry of the shoreline and wind direction.
By comparison, the last big storm surge event at Cherry Point was in 2006.
The 2006 storm surge event also coincided with a high tide event and reached 12.5 feet. That event had essentially the same storm surge of 2.5 feet, but the astronomical tide level was 0.5 feet higher in 2006 versus 2018.
Birch Bay may have other issues that will drive erosion and flooding along the shore. The road along the bay is located on top of the upper berm of the beach. Sediment deposited on the road is removed and hence the berm remains at the same level. Sediment supply to the beach has also been disrupted by the cutting through the beach to build a marina on the north of the bay and by shoreline arming on the bluffs south of the beach.
The flooding was in part the result of the initial low pressure system just off the west side of Vancouver Island. The low created pressure itself caused a sea level rise on the order of 1 foot above the astronomical tide levels. The location of the low off Vancouver Island also created winds that pushed water into the Strait of Juan de Fuca and Salish Sea. The local winds further enhanced the storm surge of tide levels. The local winds also were oriented to develop large waves in a bay that is otherwise rather calm.
The closest tide station with continuous measurements is just south of Birch Bay at Cherry Point. The storm surge at Cherry Point during the storm was 2.5 feet; a high surge for the Salish Sea.
By comparison, the last big storm surge event at Cherry Point was in 2006.
Birch Bay may have other issues that will drive erosion and flooding along the shore. The road along the bay is located on top of the upper berm of the beach. Sediment deposited on the road is removed and hence the berm remains at the same level. Sediment supply to the beach has also been disrupted by the cutting through the beach to build a marina on the north of the bay and by shoreline arming on the bluffs south of the beach.
1 comment:
WOW!!!
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