【来访单位Institution】: Texas A&M University, USA

【邀请人Host】: Steven A. Kuehl，教授

【联络人Contact】: 陈敬艳 Chen Jingyan, chenjy@xmu.edu.cn

Abstract:

Hurricane Harvey delivered 100-135 cm of rain to the Galveston Bay (GB) watershed in 5 days.  The highest of this rainfall was delivered across the heavily urbanized and industrialized bayous that drain into the upper reaches of GB, primarily from Buffalo Bayou and the San Jacinto River estuary.  The San Jacinto River and most of the other bayous that drain Houston only flooded for 7 days.  However, controlled releases from the Barker and Addicks Reservoirs into Buffalo Bayou, 50 km to the west of the confluence with the San Jacinto River, resulted in a 44-day flood through the center of Metro Houston and the heart of the petrochemical complex.  GB is normally a partially mixed estuary with its saltwedge residing within middle of the San Jacinto Estuary above the head of the bay.  The floodwaters of Harvey pushed the salt wedge of the bay, into the Gulf of Mexico. 

Analyses of vibra cores collected pre and post storm reveal that the intense, prolonged flooding in Buffalo Bayou and the San Jacinto Estuary resulted in at least 50 cm of erosion of heavily contaminated sediment and the deposition within the side embayments of over 20 cm of new sediment.  Analyses of a series of 66 push cores collected across GB revealed that Harvey deposited a 123 million m3 flood layer, containing ~98 million tons of sediment within GB-system.  This is equivalent to 22 y worth of average fluvial sediment input to the bay.  This flood layer averaged 10.45 cm thick and within the open bay was a much as 36 cm thick.  The flood layer in each core contains a basal sand layer, consistent with the anomalous transport of bedload through the bay concomitant with the advancement of the salt wedge.  Using the average concentration of Hg and the average thickness of the flood layer, we estimate that the sediment contained ~6.1 tons of mercury, tripling the surface concentration of mercury in the sediment.  It is estimated that ~5 tons of the mercury deposited in GB came from the scoured sediments of Buffalo Bayou.  It has been established in other estuaries, that an event layer 2 cm in thickness or greater, will have a devastating impact on benthic communities and interrupt the benthic pelagic coupling.  With an average 10.45 cm thick flood layer and an 3 fold increase in surface Hg concentration 3, not only was Harvey unprecedented event, Harvey had a severe and likely a devastating impact on GB.