Okaloosa County BOCC — December 6, 2016 — Sand Trace Study - ETS OkaloosaBCC 6Dec16 v3 — reading text

Sand Transport Study, East Pass, Destin, FL. Okaloosa County Board of County Commissioners Tues. 6 Dec 2016 Dr. Jon Marsh, ETS • Jon Marsh: BSc. Hons. Oceanography & Geology. PhD in sediment transport proving movement & fate of sediment in lakes, rivers, estuaries & coasts >25 years studying sediment transport. • >100 sediment transport studies worldwide: many more than anyone else • Experience/knowledge: 14 US states, 12 USACE & UK/EU, Australia & NZ - Fort Pierce Inlet, FL. (FDEP, St. Lucie County & Taylor Eng.), Pascagoula (Mobile Corps) • Specialise in sediment tracing & metocean data & measurements: critical review of past studies, evaluate modeling, identify data gaps, provide tangible & unequivocal data, provide solutions & solve real-world problems, piece together ‘jigsaw’ to complete picture… • Calibration & validation data for sediment transport models: Critical to be accurate, reflect observations & fit for purpose e.g. sediment management – public & regulators sceptical • 100% independent, neutral & no agenda • Jon Marsh: BSc. Hons. Oceanography & Geology. PhD in sediment transport proving movement & fate of sediment in lakes, rivers, estuaries & coasts >25 years studying sediment transport. • >100 sediment transport studies worldwide: many more than anyone else • Experience/knowledge: 14 US states, 12 USACE & UK/EU, Australia & NZ - Fort Pierce Inlet, FL. (FDEP, St. Lucie County & Taylor Eng.), Pascagoula (Mobile Corps) • Specialise in sediment tracing & metocean data & measurements: critical review of past studies, evaluate modelling, identify data gaps, provide tangible & unequivocal data, provide solutions & solve real-world problems, piece together ‘jigsaw’ to complete picture… • Calibration & validation data for sediment transport models: Critical to be accurate, reflect observations & fit for purpose e.g. sediment management – public & regulators sceptical • 100% independent, neutral & no agenda Why I am here today? - Lot of work, studies, modeling, measurements done in East Pass to date, but…. - Uncertainty & disagreement from lack of understanding on key processes (tidal/waves), impact of natural processes (storms) vs dredging (creating deep hollows) & borrow areas (considered minor) despite breaking longshore conveyor belt & cross-shore processes & depth of closure - Modeling as ‘good’ & as comprehensive as any other, but is flawed, inaccurate, incl. fudge factors, crude assumptions & not properly calibrated/validated & does not ‘fit’ real observations - Without certainty, understanding, accuracy – cannot manage sediment locally/regionally & ‘reacting’ - dredging, coastal erosion, nourishment projects, sand capture & transfer systems…. - Propose sand tracing study to bring all disparate info together built on real data • Fluorescent environmentally inert particles: mimic sand grains: size distribution & density • Very detectable & ideal for high energy sites: tracked >5 years & 10’s sq. miles e.g. Mouth of Columbia River, OR. - detect 1 grain in 1lb dry sand • Sediment tracers assimilate complex key 3D processes: tides, currents, waves, wind- driven circulation, bedform, burial – USACE ERDC ‘only way to measure this type of information’ • Multiple colours: label different sediments, sites, dredged material, weather conditions… • Map distribution & fate over time to determine: - transport pathways & rates - volume & mass balance - calibrate/validate numerical models - quantify size that moves & also remains… - No hope of sediment transport model predictions being correct • Current models cannot solve complex & small-scale equations of motion in 3D: (incl. Delft 3D) erosion-resuspension, settling-deposition, turbulence, bedform, burial, saltation, re- entrainment….key for nearshore beaches & inlets – author van Rijn ‘5-10 years away from starting’ • Models assume sand moves permanently as bedload OR suspended load ONLY = 2D: reality sand in constant flux – not force grains from 0.29 to 2mm in order model predicts deposition • ‘Many models are over-simplifications of complex systems that are poorly understood, calibrated or validated’ - van Rijn: - No hope of sediment transport model predictions being correct • Current models cannot solve complex & small-scale equations of motion in 3D: (incl. Delft 3D) erosion-resuspension, settling-deposition, turbulence, bedform, burial, saltation, re- entrainment….key for nearshore beaches & inlets – author van Rijn ‘5-10 years away from starting’ • Models assume sand moves permanently as bedload OR suspended load ONLY = 2D: reality sand in constant flux – not force grains from 0.29 to 2mm in order model predicts deposition • ‘Many models are over-simplifications of complex systems that are poorly understood, calibrated or validated’ - van Rijn: - Widespread avoidance of ‘difficult’ data that will highlight flaws in model/modelers - Not ground-truthed at all or with appropriate data (e.g. volume/bed level change), but which sand is being measured & where is the sand coming from or going to & where are the regional sand boundaries? - Calibrate & validate with same data or more modeling; no standardised approach, regulation or defined acceptable limits - Use off-shelf packages & assume accurate & results defined as ‘satisfactory’ are NOT - Currents depth-averaged & not near-bed where majority of sand moves - Clients/regulators unaware of limitations & assumptions & public sceptical & question predictions  Project Examples (Studies of real-life problems & providing solutions) (if time & interest) Ocean City, Philadelphia Swansea Inlet, Australia Old Bar, Australia Tweed Bypass, Australia Coos Bay, Oregon Fort Pierce Inlet, Florida Phil. USACE – Problem: required annual beach nourishment at null zone. Sand tracer study showed: - ebb shoal sand dynamics - tidal transport occurred as well, not just wave-dominated transport = some movement 24/7 - data used to validate sand transport model - study recommendations: reduce sand extraction from ebb shoal borrow site = reduction in need for beach nourishment eliminating null zone Null zone NSW Govt. Lands – Problem: annual dredging to keep channel clear (pumped to seaward beach) & areas of significant scour undermining channel sides = need to manage sediment. First step needed better understanding of system 5 sand tracer study Tidal bay: 42 sq. miles (Choctawatchee 129 sq.miles) • Greater Taree City Council – Problem: $100m sea wall or long-term sustainable/beneficial use or demolish hotel & houses • One of the highest erosion & recession rates on east coast Australia • Many companies & modelers worked at site: disagreement, ideas that were non-viable & ultimately no solution to problem – in meantime several houses demolished • 3 sand tracers released, tracked over 1 year • GTCC: study ‘de-bunked the myths surrounding sediment transport at the site’ Conclusion: considering sustainable use of sand from inlet to nourish beach using sand transfer process TRESBP (NSW & QLD Govt.) operate sand bypass: interested in regional sand management, cost share, fate of sand & %ge split between 2 states. Release pre-winter, sampling pre- & post- significant storm. Yellow arrow –tidal/river flow, Red arrows – wave driven currents BUT which sand measured in beach/bathy profile? Portland USACE monitoring 2015 – 2018 - Investigating whether dredge material returns to channel & port & recycling at significant cost - 2 colours sand tracer: Orange & Yellow - ERDC Vicksburg modeling shows monthly currents; weak in channel despite bay 20 sq miles, sand waves, instruments buried & lost, very coarse sediment & standing waves Orange – Round 1: mostly tidal processes Yellow – Round 2: winter storms Orange – Round 1: mostly tidal processes Yellow – Round 2: winter storms FDEP & St. Lucie County: 3 sand tracers (inlet & N & S beach), 3 rounds of sampling over ~9 mths; (Round 1 results released) Highlights steep project beach undercut; more unstable & no dissipation wave energy leads to higher erosion rate; ~12 hrs after release Propose (modular) sand tracing study prior to further work (e.g. Norriego Pt. & dredging): Review of previous reports, modeling & recent comprehensive beach/bathy survey data 4 main sand tracers: E & W away from ebb shoal, high erosion area to E & N Pt. (poss. N & S inlet) Metocean data incl. boundary conditions for re-modeling & Sampling 1, 3, 6 & 12 mths up to ~5km - Versatile technology: different sediment sources, dredging operations or nourishment projects to be labelled & tracked simultaneously over years (even during storms): say where sand goes & also does not.. - Proven technology in the USA with repeat clients incl. with USACE (Mobile) & FDEP - Can assist in justifying sand management projects & permitting, convincing the public & regulatory - Used to properly calibrate and/or validate a model to ensure accurate – only way to obtain key data (erosion-resuspension, settling & deposition processes) - ETS is independent & neutral & happy to work with any consulting engineers or stand alone - Versatile technology: different sediment sources, dredging operations or nourishment projects to be labelled & tracked simultaneously over years (even during storms): say where sand goes & also does not.. - Proven technology in the USA with repeat clients incl. with USACE (Mobile) & FDEP - Can assist in justifying sand management projects & permitting, convincing the public & regulatory - Used to properly calibrate and/or validate a model to ensure accurate – only way to obtain key data (erosion-resuspension, settling & deposition processes) - ETS is independent & neutral & happy to work with any consulting engineers or stand alone - Example studies range ~$150-300K depending on number & quantity of sand tracers, duration of study, number of sampling events, sampling extent & frequency, metocean data, whether model will be re-run & study repeated or sampling continued pre- and post-dredging - Propose to collect reliable & accurate dataset to provide a solution to County’s real-world problem, by: - developing a concise understanding of system integrating sand tracer data with previous studies - minimising sand in the inlet & considering sand catching/sand transfer solutions - understanding short, medium & long-term effects of both man-made (dredging & construction) & natural events, when & where to place & borrow sand, where it goes & under what conditions - providing knowledge in order to reduce costs associated with not knowing: County dealing with concerns, complaints, different viewpoints & having to manage sand often ‘reacting’ to or correcting for unexpected changes Any questions?