ASBPA 2012 - CA Tide Stations

ASBPA October 11, 2012

byJustin Vandever, PE, Coastal Engineer, AECOM

Jeremy Mull, Coastal Engineer, AECOMLauren Schmied, Michael Baker Jr, Inc.

Nicole Metzger, Oceanographer, Michael Baker Jr, Inc.Darryl Hatheway, CFM, Coastal Scientist, AECOM


Outline• Project Overview• Water Level Analysis

Tasks• Data Needs and Gaps• Methods and Analysis• Results• Methodology

Application to OtherAreas

CCAMP / OPC Study – OverviewDel Norte

Humboldt

Mendocino

Sonoma

MarinSan FranciscoSan MateoSanta Cruz

Monterey

San Luis Obispo

SantaBarbara

VenturaLosAngelesOrange

San Diego

Phase 1 (2010)Ten CountiesNorthern and CentralCalifornia Coast

Phase 2 (2012)Five Counties

SouthernCalifornia Coast

MichaelBaker Jr.

AECOM

Objective:Determine newBFEs and floodextents

QA/QC

ASBPA October 11, 2012 www.r9coastal.org

4ASBPA October 11, 2012

FEMA Pacific Guidelines

l

Statistical analysis based on 50-yr hindcast of waves and water levelsWaves and water levels are combined to compute TWL


TWL = astronomical tide + residual (surge) + setup + runupSWL = astronomical tide + residual (surge)

TWL

TWL time series Annual Maxima EVA 1% TWL (BFE)

Need hourly SWL hindcast

Water Level Analysis Tasks1. Reconstruct 50-yr stillwater level hindcast (1960-2009) for

entire CA coastlineRely on long-term observed records where availableUse predicted tide data to fill in the gaps in timeApply results spatially to fill in gaps in spaceIncorporate results to total water level calculations (stillwaterlevel + wave setup + wave run-up)

2. Extreme value analysis of annual maxima (not covered)Based on observed annual maxima dataEmploy regional frequency analysis to group gages with similarstatistical distributionsApply results spatially to map 1%-annual-chance stillwater levelin embayments and backwater areas


Tide Station Data Coverage: 1960-2009Spatial and Temporal Coverage

CharlestonPort Orford

Crescent City

Humboldt

Arena Cove

Pt ReyesSan Francisco

Monterey

San Luis

SB/RinconSanta Monica

Los AngelesNewport Bay

La JollaSan Diego

1960 20101980


La JollaCrescent City

• Station Temporal Coverage:5 tide stations >90%5 tide stations 60-90%2 tide stations 40-60%3 tide stations <40%

• Station Spatial Coverage:Continuous tidestations have goodspatial coverage fromnorthern to southern CA

Thanks to:Maria LittleTodd EhretNOAA CO-OPS

ObservedPredictedSurge = Obs - Pred


Storm of January 1988

Winter ‘83

Source: Flick and Badan-Dangon (1989)

Source: NRC (1984)

• Rely on large spatial scale of storms• Coherent regional response of residuals

to storms and El Nino conditions• Storm surge residuals are correlated

over large spatial scales

SF

MON

SLO

LA

LJ

residuals


• Storm surgeresiduals appearwell correlatedfor adjacent tidestations

• Tide stations areclosely spacedrelative to spatialextent of stormsystems

• Develop residualcorrelations andlinear regressionsamong tidestations Stations: CC=Crescent City, HU=Humboldt, AC=Arena Cove,

PR=Point Reyes, SF=San Francisco, MO=Monterey, LA=Los Angeles,NB=Newport Beach

12-hr smoothed residuals


• Exampleregressions fortwo stationspairs (MON-SFand NB-LA)

• Computecorrelationcoefficient (r)and linearregression slope– “transfercoefficient” (m)

• y-intercept = 0

r =0.90m = 0.73

r =0.96m = 0.94

MON-SF NB-LA


CH P0 CC HU AC PR SF MO SL SB RI SM LA NB LJ SDCH - 0.94 0.88 0.85 0.68 0.59 0.57 0.48 0.34 0.35 0.31 0.28 0.28 0.32 0.20 0.25P0 0.94 - 0.92 0.88 0.69 0.66 0.64 0.54 0.40 0.35 0.36 0.32 0.34 0.38 0.24 0.28CC 0.88 0.92 - 0.96 0.84 0.78 0.73 0.67 0.47 0.43 0.39 0.34 0.31 0.42 0.27 0.32HU 0.85 0.88 0.96 - 0.88 0.83 0.81 0.75 0.61 0.48 0.46 0.42 0.44 0.48 0.39 0.42AC 0.68 0.69 0.84 0.88 - 0.89 0.89 0.85 0.73 0.52 0.53 0.50 0.49 0.53 0.49 0.50PR 0.59 0.66 0.78 0.83 0.89 - 0.93 0.92 0.80 0.61 0.62 0.54 0.59 0.64 0.55 0.58SF 0.57 0.64 0.73 0.81 0.89 0.93 - 0.90 0.73 0.59 0.65 0.54 0.55 0.67 0.54 0.55

MO 0.48 0.54 0.67 0.75 0.85 0.92 0.90 - 0.90 0.74 0.73 0.65 0.73 0.77 0.71 0.73SL 0.34 0.40 0.47 0.61 0.73 0.80 0.73 0.90 - 0.82 0.82 0.71 0.74 0.85 0.72 0.75SB 0.35 0.35 0.43 0.48 0.52 0.61 0.59 0.74 0.82 - 0.93 0.80 0.84 0.87 0.79 0.87RI 0.31 0.36 0.39 0.46 0.53 0.62 0.65 0.73 0.82 0.93 - 0.67 0.89 0.89 0.82 0.78

SM 0.28 0.32 0.34 0.42 0.50 0.54 0.54 0.65 0.71 0.80 0.67 - 0.83 0.72 0.74 0.87LA 0.28 0.34 0.31 0.44 0.49 0.59 0.55 0.73 0.74 0.84 0.89 0.83 - 0.96 0.84 0.92NB 0.32 0.38 0.42 0.48 0.53 0.64 0.67 0.77 0.85 0.87 0.89 0.72 0.96 - 0.92 0.96LJ 0.20 0.24 0.27 0.39 0.49 0.55 0.54 0.71 0.72 0.79 0.82 0.74 0.84 0.92 - 0.88SD 0.25 0.28 0.32 0.42 0.50 0.58 0.55 0.73 0.75 0.87 0.78 0.87 0.92 0.96 0.88 -

Correlations for 12-hr smoothed residuals; r = 0.70 threshold


• Example ranges of spatialcorrelation (r > 0.70):

• Crescent City• Arena Cove• Los Angeles

• Residuals well correlatedover hundreds of miles

• Strong linear relationshipbetween correlation andspatial separation betweenstations

• Correlation threshold ofr=0.70 corresponds to~300 mile separation

r vs. dist.


Predictor StationCH P0 CC HU AC PR SF MO SL SB RI SM LA NB LJ SD

Infe

rred

Sta

tion

CH - 0.93 0.95 1.04P0 0.96 - 1.01 1.09CC 0.81 0.83 - 1.07 0.92 0.97 0.94HU 0.70 0.70 0.86 - 0.85 0.92 0.90 1.04AC 0.76 0.91 - 1.00 1.03 1.19 1.10PR 0.63 0.76 0.80 - 0.94 1.14 1.06SF 0.56 0.73 0.77 0.92 - 1.11 0.89

MO 0.54 0.61 0.73 0.73 - 0.96 0.72 0.75 0.84 0.87 0.81 0.83SL 0.49 0.60 0.60 0.85 - 0.76 0.77 0.67 0.86 0.91 0.81 0.84SB 0.74 0.86 - 0.93 0.78 0.99 1.12 0.85 0.99RI 0.72 0.85 0.86 - 0.95 0.98 0.96 0.82

SM 0.73 0.83 - 0.93 0.95 0.80 0.90LA 0.63 0.64 0.72 0.77 0.72 - 0.96 0.82 0.91NB 0.68 0.80 0.69 0.81 0.54 0.94 - 0.97 0.93LJ 0.63 0.63 0.70 0.68 0.65 0.87 0.88 - 0.90SD 0.66 0.67 0.76 0.78 0.79 0.93 0.97 0.87 -


Inferred Residual Method Transferred Residual MethodInferred Station: Monterey (MON)Predictor Station: San Francisco (SF)

Correlation Coefficient, r = 0.90Transfer Coefficient, m = 0.73

SWLMON = (Pred. Tide)MON +0.73*(Obs. Res.)SF

Inferred Station: Shelter Cove (SC)Transfer Station: Humboldt (HU)

Apply direct 1:1 transfer of residualto subordinate station

SWLSC = (Pred. Tide)SC +(Obs. Res.)HU


ObservedRecord

Predictor Stations(% and corr. coeff.)

OtherStations

Infe

rred

Sta

tion

Crescent City 96% 4%Humboldt 64% CC (35%, 0.96) 1%

Arena Cove 45% SF (30%, 0.89) & PR (25%, 0.89) <1%Point Reyes 69% SF (31%, 0.93) <1%

San Francisco 99% <1%Monterey 72% SF (27%, 0.90) 1%

Port San Luis 94% 6%Santa Barbara 26% SD (33%, 0.87), LA (20%, 0.84), RI (20%, 0.93) 1%Santa Monica 68% LA (21%, 0.83) & SD (12%, 0.87) <1%Los Angeles 98% 2%

Newport Bay 29% LA (70%, 0.96) 1%La Jolla 94% 6%

San Diego 66% LA (21%, 0.92) & NB (14%, 0.96) <1%

At all stations, predicted tide required for only <0.1% of record

1960-2009 Hindcast Period


Coastal ReachWater Level

Record1 Del Norte coast Crescent City

(9419750)2 Humboldt coast Humboldt Bay,

North Spit(9418767)

3 Humboldt-Mendocino coast

Shelter Cove(9418024)*

4 Mendocino-Sonomacoast

Arena Cove(9416841)

5 Sonoma-Marin coast Point Reyes(9415020)

Spatial application to reachesvs. interpolating results


Coastal ReachWater Level

Record6 Golden Gate coast San Francisco

(9414290)7 San Francisco Coast Ocean Beach

(9414275)*8 San Mateo coast Princeton, Half

Moon Bay(9414129)*

9 Santa Cruz coast Año NuevoIsland

(9413878)*10 Monterey Bay coast Monterey

(9413450)11 Big Sur, Monterey coast Monterey

(9413450)12 San Luis Obispo coast Port San Luis

(9412110)

*Subordinate stations


Coastal Reach

RecommendedWater Level

Record13 Santa Barbara-Ventura

coastSanta Barbara

(9411340)14 Ventura-Santa Monica

coastSanta Monica

(9410840)15 Los Angeles-Orange

coastLos Angeles(9410660)

15a Newport Bay Newport BayEntrance

(9410580)16 San Diego open coast La Jolla

(9410230)16a San Diego Bay San Diego

(9410170)


• Acceptable for the open Pacific coast because:Large spatial extent of storms/El Nino effectsRelatively dense spatial distribution of tide stationsResidual impacts multiple stations similarlyFew instances of widespread temporal data gapsGood spatial distribution of continuous stations (Crescent Cityto La Jolla)Relatively small magnitude of residuals relative to TWLTWL dominated by tides and wave effects

• Applicable to other areas affected by large-scale meteorologicalphenomena and storms

• Meteorological phenomena with high spatial variability, such ashurricanes, would not be well suited for this methodology

Questions?Questions?


Big Sur River, Andrew Molera State Park

Justin Vandever, PEAECOMOakland, [email protected]

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ASBPA 2012 - CA Tide Stations

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