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• 1. [Article] Channel Shallowing as Mitigation of Coastal Flooding

  Here, we demonstrate that reductions in the depth of inlets or estuary channels can be used to reduce or prevent coastal flooding. A validated hydrodynamic model of Jamaica Bay, New York City (NYC), is ...

  Citation × Citation Citation Abstract Copy Title: Channel Shallowing as Mitigation of Coastal Flooding Author: Orton, Philip M., Talke, Stefan A., Jay, David A., Yin, Larry, Blumberg, Alan F., Georgas, Nickitas, Zhao, Haihong, Roberts, Hugh J., MacManus, Kytt Year: 2015 Here, we demonstrate that reductions in the depth of inlets or estuary channels can be used to reduce or prevent coastal flooding. A validated hydrodynamic model of Jamaica Bay, New York City (NYC), is used to test nature-based adaptation measures in ameliorating flooding for NYC’s two largest historical coastal flood events. In addition to control runs with modern bathymetry, three altered landscape scenarios are tested: (1) increasing the area of wetlands to their 1879 footprint and bathymetry, but leaving deep shipping channels unaltered; (2) shallowing all areas deeper than 2 m in the bay to be 2 m below Mean Low Water; (3) shallowing only the narrowest part of the inlet to the bay. These three scenarios are deliberately extreme and designed to evaluate the leverage each approach exerts on water levels. They result in peak water level reductions of 0.3%, 15%, and 6.8% for Hurricane Sandy, and 2.4%, 46% and 30% for the Category-3 hurricane of 1821, respectively (bay-wide averages). These results suggest that shallowing can provide greater flood protection than wetland restoration, and it is particularly effective at reducing "fast-pulse" storm surges that rise and fall quickly over several hours, like that of the 1821 storm. Nonetheless, the goal of flood mitigation must be weighed against economic, navigation, and ecological needs, and practical concerns such as the availability of sediment. Title: Channel Shallowing as Mitigation of Coastal Flooding Author: Orton, Philip M., Talke, Stefan A., Jay, David A., Yin, Larry, Blumberg, Alan F., Georgas, Nickitas, Zhao, Haihong, Roberts, Hugh J., MacManus, Kytt Year: 2015 Here, we demonstrate that reductions in the depth of inlets or estuary channels can be used to reduce or prevent coastal flooding. A validated hydrodynamic model of Jamaica Bay, New York City (NYC), is used to test nature-based adaptation measures in ameliorating flooding for NYC’s two largest historical coastal flood events. In addition to control runs with modern bathymetry, three altered landscape scenarios are tested: (1) increasing the area of wetlands to their 1879 footprint and bathymetry, but leaving deep shipping channels unaltered; (2) shallowing all areas deeper than 2 m in the bay to be 2 m below Mean Low Water; (3) shallowing only the narrowest part of the inlet to the bay. These three scenarios are deliberately extreme and designed to evaluate the leverage each approach exerts on water levels. They result in peak water level reductions of 0.3%, 15%, and 6.8% for Hurricane Sandy, and 2.4%, 46% and 30% for the Category-3 hurricane of 1821, respectively (bay-wide averages). These results suggest that shallowing can provide greater flood protection than wetland restoration, and it is particularly effective at reducing "fast-pulse" storm surges that rise and fall quickly over several hours, like that of the 1821 storm. Nonetheless, the goal of flood mitigation must be weighed against economic, navigation, and ecological needs, and practical concerns such as the availability of sediment. Close

• 2. [Article] Estimation of Historic Flows and Sediment Loads to San Francisco Bay, 1849 – 2011

  River flow and sediment transport in estuaries influence morphological development over decadal and century time scales, but hydrological and sedimentological records are typically too short to adequately ...

  Citation × Citation Citation Abstract Copy Title: Estimation of Historic Flows and Sediment Loads to San Francisco Bay, 1849 – 2011 Author: Moftakhari Rostamkhani, Hamed, Jay, David A., Talke, Stefan A., Schoellhamer, David H. Year: 2015 River flow and sediment transport in estuaries influence morphological development over decadal and century time scales, but hydrological and sedimentological records are typically too short to adequately characterize long-term trends. In this study, we recover archival records and apply a rating curve approach to develop the first instrumental estimates of daily delta inflow and sediment loads to San Francisco Bay (1849 – 1929). The total sediment load is constrained using sedimentation/erosion estimated from bathymetric survey data to produce continuous daily sediment transport estimates from 1849 to 1955, the time period prior to sediment load measurements. We estimate that ~55% (45 – 75%) of the ~1500±400 million tons (Mt) of sediment delivered to the estuary between 1849 and 2011 was the result of anthropogenic alteration in the watershed that increased sediment supply. Also, the seasonal timing of sediment flux events has shifted because significant spring-melt floods have decreased, causing estimated springtime transport (April 1st to June 30th) to decrease from ~25% to ~15% of the annual total. By contrast, wintertime sediment loads (December 1st to March 31st) have increased from ~70% to ~80%. A ~35% reduction of annual flow since the 19th century along with decreased sediment supply has resulted in a ~50% reduction in annual sediment delivery. The methods developed in this study can be applied to other systems for which unanalyzed historic data exist. Title: Estimation of Historic Flows and Sediment Loads to San Francisco Bay, 1849 – 2011 Author: Moftakhari Rostamkhani, Hamed, Jay, David A., Talke, Stefan A., Schoellhamer, David H. Year: 2015 River flow and sediment transport in estuaries influence morphological development over decadal and century time scales, but hydrological and sedimentological records are typically too short to adequately characterize long-term trends. In this study, we recover archival records and apply a rating curve approach to develop the first instrumental estimates of daily delta inflow and sediment loads to San Francisco Bay (1849 – 1929). The total sediment load is constrained using sedimentation/erosion estimated from bathymetric survey data to produce continuous daily sediment transport estimates from 1849 to 1955, the time period prior to sediment load measurements. We estimate that ~55% (45 – 75%) of the ~1500±400 million tons (Mt) of sediment delivered to the estuary between 1849 and 2011 was the result of anthropogenic alteration in the watershed that increased sediment supply. Also, the seasonal timing of sediment flux events has shifted because significant spring-melt floods have decreased, causing estimated springtime transport (April 1st to June 30th) to decrease from ~25% to ~15% of the annual total. By contrast, wintertime sediment loads (December 1st to March 31st) have increased from ~70% to ~80%. A ~35% reduction of annual flow since the 19th century along with decreased sediment supply has resulted in a ~50% reduction in annual sediment delivery. The methods developed in this study can be applied to other systems for which unanalyzed historic data exist. Close