Shoreline Erosion Management 101 to Support Chesapeake Bay Health

Transcription

1 Shoreline Erosion Management 101 to Support Chesapeake Bay Health

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7 Speaker Info Rich Ortt Maryland Geological Survey Maryland Department of Natural Resources Daniel Proctor Stantec Bill Stack Center for Watershed Protection

8 Today s Agenda Sediment Delivery and Shoreline Erosion in the Chesapeake Bay Different management practices for tidal shorelines Expert Panel Review of Shoreline Management Practices + Next Steps

9 Sediment Delivery and Shoreline A Historic Look at Sediment Delivery and Erosion in the Chesapeake Bay Coastal Systems June 12, 2015 Richard A. Ortt, Jr. Maryland Geological Survey MD-Department of Natural Resources

10 Chesapeake Bay 200 miles long (320 km) 6 to 35 miles wide (10-56 km) Average depth of ~ 7 meters 20% less than 2 meters depth Huge watershed area relative to volume Microtidal max range just over ½ meter 50% freshwater from Susquehanna River 90% freshwater from 5 major rivers

11 Dominant Sediment Sources Watershed Fluvial Shore Erosion Oceanic Input Internal Production Complicating Factor Internal Redistribution - Resuspension

12 Sources and pathways of sediments in the Bay Fluvial watershed Shore erosion Oceanic input Internal production Resuspension

13 MODIS 3/22/05

14 MODIS 4/09/05

15 Tropical Storm Lee: Fall 2011

16 Sediment Load (millions of tons) 120 Estimated Susquehanna River Load to Reservoirs Susquehanna Sediment Input Sediment Load Year

17 Sources and pathways of sediments in the Bay Fluvial watershed 4.27 x 10 6 metric tons/yr Number is constantly being refined. Shore erosion Oceanic input Internal production Resuspension

18 Sources and pathways of sediments in the Bay Fluvial watershed Shore erosion Oceanic input Internal production Resuspension

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22 Relative Sea Level Curve for the Chesapeake Bay Area From 10,000 to 7,000 years ago Rise from -60 m to -20 meters = 13 mm/yr From 6,000 to present. Rise from -10 meters = 1.67 mm/yr

23 Baltimore Tide Gauge Record Last 100 years sea level rise of 30 cm = 3 mm/year

24 What is Shore Erosion?

25 Shore Erosion Fastland & Nearshore

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27 Shoreline Erosion KG/M/Day Shoreline Erosion KG/M/Day

28 ENTIRE BAY SHORE EROSION MASS LOADING AVERAGED Annual MD VA Length (total) (m) 2,912,000 4,060,000 Length (unprotected) 1,993,000 3,276,000 % Protected Loading MT/yr - total Fines Coarse Organic Loading (kg/m/day) - total Fines Coarse Organic 2,733,000 1,503,000 1,153,000 77, ,500, , ,

29 Nutrient Loads associated with Shoreline Erosion Virginia Ibison et al., 1990 Virginia Ibison et al., 1992 Maryland Hill et al., 2003 Average Total N (kg/m-yr) Standard Deviation Average Total P (kg/m-yr) Standard Deviation Nutrient numbers are highly variable depending upon shoreline type.

30 Sources and pathways of sediments in the Bay Fluvial watershed 4.27 x 10 6 metric tons/yr Shore erosion 4.23 x 10 6 metric tons/yr Oceanic input Geologically the largest Currently about 1 x 10 6 metric tons/yr Internal production Total Suspended Solids vs. Total Suspended Sediment

31 Sources of Sediment in Chesapeake Bay

32 REF: Wayne L. Newell, Inga Clark, Owen Bricker 2004

33 From an Ecosystem Perspective Not all Sediment Input is Detrimental Sand component Remains near source Forms Beaches Limited habitat type in the Bay Recreational value Buffers shore against continued erosion Necessary for healthy SAV Constantly being reaffirmed by recent studies.

34 From an Ecosystem Perspective Not all Sediment Input is Detrimental Silt/Clay (Mud) Component Transported in suspension away from source Close affinity with nutrients Attenuates light, adversely affecting SAV Interferes with filter feeding organisms Contributes to burial of sessile benthic organisms (oysters) Necessitates dredging shipping channels Serves as sediment supply to tidal marshes, enhancing ability to keep pace with sea level rise

35 Chesapeake Bay Program: Sediment Work Group USGS Publication : WRIR /wrir pdf pub/wrir pdf

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37 Types of Shoreline Stabilization Practices June 18, 2015 Daniel Proctor, PE Stantec

38 Safety Moment Shoreline management is about more than just erosion control or water quality it s about safety. I wouldn t want my kids playing in this backyard! Source: USGS

39 Agenda 1 Structural Practices 2 Living Shorelines 3 How to Choose?

40 1 Structural Practices Everything should be made as simple as possible, but not simpler. Albert Einstein

41 Structural Practices Bulkhead/Seawall Hardened shoreline (concrete, timber, vinyl, or steel sheet piles) Industrial or commercial waterfront areas Traditional preference for residential lots Revetment Riprap armoring of bank Often in conjunction with bank grading Windrow stacked riprap at toe instead of bank armoring Groins/Jetties Protruding structures perpendicular to shoreline (typ. riprap) Groins series of structures along a shoreline Jetty at inlets or harbors to aid in boat navigation & protection Breakwaters Stacked riprap mounds Parallel and offset from shoreline

42 Bulkhead Source: Crane Materials International (CMI)

43 Seawall

44 Revetment

45 Breakwaters

46 2 Living Shorelines Or whatever you want to call it Living shorelines, non-structural practices, bioengineering techniques, green shorelines, soft shoreline stabilization, ecosystem restoration, natural design, environmentally friendly, all natural, eco-friendly, etc.

47 Living Shorelines: Non-Structural Beach Nourishment Placement of sand and/or vegetation Widen existing beach or restore eroded beach profile Marsh Creation Gentle, intertidal nourishment Establishment of marsh vegetation Vegetated Bank Stabilization Bank grading, seeding/planting, and temporary matting Coir logs along toe Oyster Reefs Submerged substrate conducive to oyster growth Can serve as a submerged breakwater Dune Enhancement Creation or improvement of a sand dune system Provides inland protection from larger storms

48 Living Shorelines: Hybrid Marsh Sill Marsh creation with stacked riprap along waterline Typically lower elevations than breakwaters Gaps in sill to allow for biological exchange Breakwater Hybrid System Combine nearshore breakwaters with nourishment Pre-fill tombolo with sand and/or marsh vegetation Helps avoid disruption of longshore sediment transport Others Any combination of rock structures with living shorelines

49 Beach Nourishment Source: U.S. Army Corps of Engineers, Virginia Beach Nourishment

50 Marsh Creation

51 Vegetated Bank Stabilization

52 Marsh Sill Source: Center for Coastal Resources Management (ccrm.vims.edu/livingshorelines/photo_gallery.html), Virginia Institute of Marine Science.

53 Breakwater Hybrid System Oyster Reef

54 Breakwater Hybrid System

55 3 How to Choose? Source: HikingArtist.com

56 Selection Considerations Site Configuration Orientation (with respect to typical wind direction) Bank elevation and slope Beach profile Offshore water depths Composition of beach & bank sediments Existing wetlands & submerged aquatic vegetation (SAV) Riparian buffer conditions Hydrodynamic Conditions Fetch (available water distance offshore) Wind speed and magnitude Wave heights Tide range Storm surge Erosion rate Longshore sediment transport direction & rate

57 Selection Considerations Permitting Constraints Living shorelines preferred Limit encroachment beyond mean low water (MLW) Avoid impacts to existing wetlands and SAV Riparian buffer impacts Available Project Budget Wide range in costs Pay attention to amount of bank grading, sand fill, and riprap Grant funding potential Monetary value of resulting nutrient reduction credit Level of Protection Needed Damage potential / risk-reward analysis Rural vs. Urban setting Proximity of residences or critical infrastructure 100-year storm?

58 Questions? Daniel Proctor, PE Stantec

59 Chesapeake Bay Stormwater Training Partnership Webcast June 18, 2015 Bill Stack, P.E. Shoreline Management Expert Panel Chair EPA CBPO Sediment Reduction and Stream Restoration Coordinator Center for Watershed Protection, Inc.

60 Shoreline Management Panel Members Panelist Jana Davis, Ph.D. Kevin DuBois, PWS, PWD Jeff Halka Scott Hardaway, P.G. George Janek Lee Karrh Eva Koch, Ph.D. Lewis Linker Pam Mason Ed Morgereth, MS ISS Daniel Proctor, P.E. Kevin Smith Bill Stack, P.E. Steve Stewart/Nathan Forand Bill Wolinski, P.E. Affiliation CBT/HGIT City of Norfolk, VA MD Geologic Survey, retired VIMS Shoreline Studies Program USACE, Norfolk District MD DNR UMCES CBPO VIMS Center for Coastal Resource Management Biohabitats Stantec (formerly Williamsburg Environmental Group) MD DNR CWP, CBPO Baltimore County Dept. of Environmental Protection and Sustainability Talbot County Dept. of Public Works

61 Expert Panel Charge Define practice Define geographical range Conduct literature review Develop protocols (if warranted) Determine qualifying conditions Develop reporting and verification guidance Recommend research needs

62 BMP EXPERT PANEL URBAN STORMWATER WORKGROUP WATERSHED TECHNICAL WORKGROUP WATER QUALITY GIT Jan - March Expert Panel Work April August --- Dec End July panel meetings involving research, discussions, and recommendations WTWG issues related to model resolved

63 Expert Panel Definition Shoreline management is defined as any tidal shoreline practice that prevents and/or reduces tidal sediments to the Bay.

64 Why there is the need for new reduction rates Shoreline BMPs were lumped together and reported with stream restoration practices. Shoreline erosion is one of the greatest sources of sediment and turbidity to the Chesapeake Bay. The literature supports development of protocols for estimating pollutant shoreline management rates.

65 Comparing the Numbers: Shoreline Erosion Loading Rates Source TN (lb per foot per year) TP (lb per foot per year) TSS (lb per foot per year) Ibison, ,000 Ibison, ,800 Proctor, 2012 na 1, or 0.29 (WEG) MDE, 2011* BaCo (mean) CBP Stream (2010) CBP Stream (Aug 2013) (non-coastal plain) *MDE data based on Baltimore Co. DEPS analysis of 23 individual shoreline restoration projects completed by Baltimore Co. DEPS Capital Projects and Operations. Median values were used. (Nathan Forand presentation to the SEC panel on 2/25/13)

66 Protocols based on processes associated with sediment and nutrient removal Prevented Sediment Tidal Marsh Denitrification Sediment Trapping through Accretion Marsh Redfield Ratio

67 Prevented Sediment Prevention of tidal shoreline sediments through structural (revetments) or hybrid systems. Removal rates are determined based on monitoring data or average shoreline erosion rates. Assumes 100% effective. Why? The removal rate is only given for the percentage of fine sediment which is also available from DNR and VIMS.

68 Tidal Marsh Denitrification Average denitrification rates are averaged from studies of tidal marshes and multiplied time the marsh area.

69 Sediment Trapping through Accretion Reviewed literature studies in the Chesapeake Bay tributaries to determine the annual sediment accretion rate for tidal marshes and TP associated with these sediments. USGS, Patuxent Wildlife Refuge This averaged rate is then multiplied times the surface area of the created marsh.

70 Marsh Redfield Ratio The Marsh Redfield ratio which is the ratio of C:N:P in the standing crop of marsh vegetation was not that variable and was hence averaged and used to estimate and annualized reduction credit. The surface area of the created marsh is multiplied by the average per square meter values determined from the literature. (i.e., 23 g TN m -2 and 1 g TP m -2 ) and annualized.

71 Average erosion rates used for Default rate Annual MD VA Length (total) (meters) 2,912,000 4,060,000 Length (unprotected) (meters) 1,993,000 3,276,000 % Protected Loading MT/yr - total Fines Coarse Organic Loading (kg/m/day) - total Fines Coarse Organic m = meters MT = metric tons 2,733,000 1,503,000 1,153,000 77, ,500, , , Chesapeake Bay shoreline characteristics and shoreline erosion mass loading (averaged) (Halka, 2013).

72 Summary of shoreline management pollutant load reduction for individual projects Protocol Submitted Unit Total Nitrogen (lbs per unit) Total Phosphorus (lbs per unit) Total Suspended Sediment (lbs per unit) Protocol 1 - Prevented Sediment Protocol 2 Denitrification Protocol 3 - Sedimentation Protocol 4 Marsh Redfield Ratio Linear Feet NA at this time* NA at this time* Project-Specific Acres of revegetation 85 NA NA Acres of revegetation NA ,959 Acres of revegetation NA Non-conforming/Existing Practices Linear Feet (NA at this time)* (NA at this time)* 164/42**

73 Issues raised regarding Protocol 1 Protocol 1 BMPs remove sand (which is beneficial) in addition to fine sediment. Projects involving armoring should not receive any credit because of negative impact to aquatic life Note: WTWG recommended to eliminate the nutrient credit for Protocol 1 pending further study.

74 Issues raised by regarding Protocol 1 Concerns raised about the availability/reactivity of TP and TN associated with shoreline sediments and the impact that nutrient crediting might have on TMDL accounting. Concerns that the cumulative BMP loading reductions could possibly exceed available simulated loadings.

75 Response to Issues State agency flexibility when SAV s are impacted Protocol 1 only for TSS approval at this time Modeling Team to study sediment/nutrient reactivity Fine sediment cap based on WQSTM analysis

76 Baltimore County Example Three reaches along the Back River shoreline were identified as severely eroded and in need of stabilization (Figure 5). The first reach (reach 2) had a variable 6 to 8 foot high vertical bank along 1,079 feet on the north end of Essex Skypark (Figure 6). The fetch is approximately 2.9 miles and the shoreline is subject to significant wind-generated wave action. Many trees along the shoreline fell. This exposed the clay soils and resulted in bank recession. The second reach (reach 5A) includes a total of 881 linear (LF) and the third reach (reach 5B) includes 650 LF on the south end of the property with a bank height ranging from 3 to 5 feet along the shoreline (Figure 6). The rate of erosion on the north shoreline averaged of 1.5 feet per year and on the south shoreline averaged 1.0 foot per year. The shoreline management project included structural and non-structural erosion control and shoreline enhancement techniques along 2,610 LF including the creation of a living shoreline planted with 79,513 square feet of wetland grasses that were protected by 12 off shore stone sills and 5 off shore stone breakwaters. Table 13 outlines the protocol 1 Prevented Sediment values.

77 BC Example Pollutant Protocol 1 Pollutant Load Reduction (lb/yr) Protocol 2 Pollutant Load Reduction (lb/yr) Protocol 3 Pollutant Load Reduction (lb/yr) Protocol 4 Pollutant Load Reduction (lb) 1 Total Pollutant Load Reduction (lb/yr) 2 TN NA 153 NA TP NA NA TSS 450,070 NA 12,526 NA 462,596 1 Marsh Redfield Ratio pollutant load reduction if a one-time credit. 2 This practice was 2,610 linear feet, had an erosion rate of 1 and 1.5 ft/yr, had a bank height of 4 and 7 feet, and had 1.8 acres of vegetation.

78 Accountability Reporting, tracking, and verification Name, location, permit number, county, location, practice type, and vegetation area Initial performance verification responsible crediting party provide post construction documentation to the reporting agency Duration of shoreline management credit 5 years Can be renewed, future verification principles

79 Questions/Comments Bill Stack, P.E. or xt 222 or

80 Questions?

81 Webcast Resources A Summary Report of Sediment Processes in Chesapeake Bay and Watershed Updating Maryland s Sea-level Rise Projections: Special Report of the Scientific and Technical Working Group to the Maryland Climate Change Commission. June 2013 Shoreline Management Suggested Reading references The expert panel final report - Coming soon!

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