Sediment Quantity and Dynamics
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Delaware Estuary Regional Sediment Management Plan White Paper Appendix A: SEDIMENT QUANTITY AND DYNAMICS Last Revised: February 28, 2011 Final Draft – September 2012 Delaware Estuary Regional Sediment Management Plan Sediment Quantity and Dynamics White Paper Table of Contents Introduction ............................................................................................................................. 1 The Delaware Estuary Sediment System ................................................................................. 3 Shorelines and Channels .................................................................................................. 3 Upland Sediment Supply ................................................................................................... 3 Sediment Budget ............................................................................................................... 7 Sediment Classification and Distribution ........................................................................... 7 Delaware Estuary Sediment Budget – Quantities and Transport Mechanisms ................... 9 Sources and Sinks ............................................................................................................ 9 Dynamic Factors – Estuarine Turbidity Maximum (ETM) and Principal Transport Mechanisms ........................................................................................................ 10 Nomenclature ...................................................................................................... 10 Estuary Turbidity Maximum (ETM) Overview ...................................................... 11 Fluvial Transport .................................................................................................. 11 Tidal Transport .................................................................................................... 11 Gravitational Circulation ...................................................................................... 13 Tidal Pumping ..................................................................................................... 13 Observations of Sediment Transport and the ETM in the Lower Estuary ....................... 13 Long Range Spoil Disposal Study ....................................................................... 13 UD Observations in 2003 .................................................................................... 14 UD Observations in 2005 .................................................................................... 15 Maintenance Dredging Trends ........................................................................................ 17 Sediment Transport in Delaware Bay ............................................................................. 17 Ongoing Sediment Budget Research .............................................................................. 21 Principal Conclusions ............................................................................................................. 22 Remaining Problems/Questions to Address ......................................................................... 23 Sediment Budget ............................................................................................................. 23 Marsh Sediment Budget .................................................................................................. 23 Coarse-grained Sediments ............................................................................................. 23 Dredging .......................................................................................................................... 23 Geochemistry and Biochemistry ..................................................................................... 24 Fine-grained Sediment Transport in the Bay .................................................................. 24 Mechanisms of Marsh Loss ............................................................................................ 24 Sediment Transport Pathways ........................................................................................ 24 Model ............................................................................................................................ 24 References Cited ...................................................................................................................... 26 Sediment Quantity and Dynamics White Paper Committee ................................................. 29 Delaware Estuary Regional Sediment Management Plan i Sediment Quantity and Dynamics White Paper Appendix A: Summary - Long Range Spoil Disposal Study, Sub-Study 2 “Nature, Source, and Cause of the Shoal” (USACE, 1973) ....................................... A-1 Sediment Budget (pages 29 - 42) ................................................................................. A-1 Sediment Contributions to the Estuary .............................................................. A-2 Sediment Shoaling in Navigation Channels ...................................................... A-2 Suspended Sediment Transport (pages 42 - 87) .......................................................... A-3 List of Tables Table 1: Land Use/Cover in the Delaware River Basin ................................................................ 4 Table 2: Northeast Region Cropland Erosion Rates (1982-2007) ............................................... 6 Table 3: Relative Erosion Rates and Delivery Ratios for Sediment Delivery in the Lockatong and Wickecheoke Creek Watersheds .................................................. 6 Table 4: 1950-1985 Estuary Sediment Mass Balance ................................................................. 9 Table 5: Delaware Estuary Zones .............................................................................................. 10 List of Figures Figure 1: Location Map ................................................................................................................ 2 Figure 2: Annual Suspended Load Time Series .......................................................................... 5 Figure 3: Bottom Sediment Distribution (Biggs and Church, 1984) ............................................. 8 Figure 4: Suspended Sediment Distribution .............................................................................. 12 Figure 5: Location Map for UD 2005 Observations (Sommerfield, “Understanding Turbidity in the Delaware Estuary”, 2007 Delaware Estuary Science Conference) .......... 16 Figure 6: High Maintenance Dredging Areas ............................................................................. 18 Figure 7: Maintenance Dredging Rates ..................................................................................... 19 Figure 8: Cumulative Maintenance Dredging, Federal Navigation Projects in Delaware Estuary, 1997 - 2009 ........................................................................................... 20 Delaware Estuary Regional Sediment Management Plan ii Sediment Quantity and Dynamics White Paper Acronyms and Abbreviations BC Blackbird Creek BH Bombay Hook C&D Canal Chesapeake and Delaware Canal CEAP Conservation Effects Assessment Project DMB Delaware Memorial Bridge ETM Estuarine Turbidity Maximum LRSDS Long Range Spoil Disposal Study NC New Castle NRI National Resource Inventory RSM Regional Sediment Management SSC suspended sediment concentration UD University of Delaware USGS U.S. Geological Survey WHG Woods Hole Group Delaware Estuary Regional Sediment Management Plan iii Sediment Quantity and Dynamics White Paper Introduction Sediment is an integral and natural component of the Delaware estuary. It is one element of a complex estuarine system that includes processes associated with biology, biochemistry, geology, geochemistry, hydrology, tidal hydraulics, and meteorology. The processes interact within a continuum of spatial and temporal scales to influence the behavior and “health” of the ecosystem. Sediment as bottom/riverbed substrate supports a wide variety of habitats and ecosystems that extend from the fresh water zone in the tidal river above Philadelphia to the sandy, saline environment at the Capes. (Figure 1) Sediment accumulates in channels and harbors of the estuary, interferes with safe and efficient navigation, and necessitates dredging and ultimately disposal. Suspended sediments play a role in the transport of nutrients and adsorb dissolved toxic substances such as trace metals, pesticides, and PCBs. Suspended sediment creates turbidity, which limits penetration of light into the water column and affects photosynthesis. The goal of regional sediment management (RSM) is to consider sediment as a resource critical to the economic and environmental vitality of the region. Sediment is often regarded as a localized waste product or pollutant to be disposed of as cost effectively as possible. When sediment is removed for navigation purposes, it is desirable to maximize the beneficial uses of the dredged material. Until the Delaware Estuary RSM program was initiated in 2009, there was no systematic, collaborative approach to dealing with the challenges and opportunities associated with sediment in the estuary. To date, all attempts at beneficial use of dredged sediments have been accomplished on an ad hoc, project-specific basis. The present RSM initiative is intended to broaden local knowledge about how, where, and when to manage parts of the sediment system differently and more beneficially than has been