Humboldt Bay Vertical Reference System Working Group (HumBayVert) Summary of Findings & Science Plan Update Jul-8-2011

Cascadia GeoSciences, Northern Hydrology, HSU Geology, U of O Geology, & HBI members

First Workshop Oct. 21, 2010

What was discussed?

Land level influencing local sea level Discuss geologic processes Review regional & local sea level Discuss logistics of re-leveling HumBay

Mission and Goals

Determine historic land and sea level trends Map local sea level change across region Complete historic analysis of tide and level data in PNW Model geologic processes controlling uplift/subsidence Compare historic trends to prehistoric geologic record Data dissemination for regional workers

Methods

Re-occupy historic tide gage locations Install regional tide gage stations Collect and analyze historic GPS & level data WRT mean sea level Model Cascadia Subduction Zone with new data Partnerships & collaboration

Bathymetry and topography of the Cascadia subduction zone

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Bathymetry and topography of the Cascadia subduction zone

We live and work here!

Atwater & Satake, 2009

H. Kelsey, HSU, 2001

Eustatic SeaLevel Rise

(ESLR)

TideGauges

Leveling & GPS

Compare Rates & Test Observations

Compare to tide gageobservations

Compare to GPS and land level surveys

Compare to long term ESLR

Historic Temporary Tide Gage Locations, Humboldt Bay1977-1980

1931: San Jose – Eureka1931: Eureka – Grants Pass1944: Arcata – North Spit1967: Longvale – Crescent City1988: Eureka – Redding1988: Westport – Arcata – North Spit1992: Garberville – Loleta2004: State Hwy – Countywide GPS

Source: NGS Integrated Database; compiled by Don Campbell, CalTrans Dist. 1, 2010.

Historic Leveling,Humboldt Bay

HistoricLevelSurveys:

Weldon et al;Univ. of Oregon

GPS Data:

USGS processing of EarthScope and other GPS stations.

Rate of sea-level rise ~2.3 mm/yr

(1977-2010)

1975 1980 1985 1990 1995 2000 2005 2010 20153.05

3.1

3.15

3.2

3.25

3.3

3.35

3.4

3.45

f(x) = 0.00541644496829089 x − 7.48308026515361North Spit minus Crescent City

Both NOAA’s calculated absolute sea level trend estimates and the more precise difference between the two sites suggest that North Spit subsides relative to Crescent City at about ~5.4 mm/yr. Given eustatic sea level rise of ~2.3 mm/yr for 1977 to 2010, Crescent City rises, absolutely, at ~3 mm/yr and North Spit sinks at about ~2.5 mm/yr.

Northcoast Sea Level

Ray Weldon, Oct. 2010

GPS Vertical Rates WRT to CCPBO USGS

Mad River Slough Relative to Crescent City

•Mad River Slough subsides relative to Crescent City at 4.2 mm/yr. •This indicates that Mad River Slough is sinking at a rate 1.2 mm/yr less than North Spit (5.4 mm/yr).

y = 4.2x - 8,785.2

-500

-450

-400

-350

-300

-25019

75

1980

1985

1990

1995

2000

2005

2010

Mon

thly

Mea

n Se

a Le

vel (

mm

-on

stati

on d

atum

)

Year

Mad River Slough minus Crescent City, for NOAA 1978,79 and NHE 2008 Mean Sea Level Data

1978-79 Data 2008 Data Linear (1978-79, 2008 Data)

Mad River Slough Relative to North Spit

•Mad River Slough subsides 0.9 mm/yr less than North Spit. •This estimate is close to above rate of 1.2 mm/yr.•The Crescent City estimate is probably more accurate due to length of record.

y = -0.92x - 1,862.91

-3750

-3740

-3730

-3720

-3710

-3700

-3690

-3680

-3670

-3660

-3650

1975

1980

1985

1990

1995

2000

2005

2010

Mon

thly

Mea

n Se

a Le

vel (

mm

-on

stati

on d

atum

)

Year

Mad River Slough minus North Spit, for NOAA 1978,79 and NHE 2008 Mean Sea Level Data

1978-79 Data 2008 Data Linear (1978-79, 2008 Data)

Jeff Anderson, Northern Hydrology Engineering, Jan. 28 2010, HBI Meeting

GPS Vertical RatesPBO USGS

Crescent City: 2.3 (ESL) - -0.8 (RSL) = + 3.1 GPS Station: PTSG = + 2.2 ± 0.8

North Spit (a) : 2.3 (ESL) – 4.1 (RSL) = - 1.8 (b) : - 5.4 (NS-CC) + (CC UL) = - 2.3 to -3.2

Interpolated w/ GPS Stations: ((P162-P058)/2))+P058 = - 1.9 ± 0.6

Mad River Slough (a) : 2.3 (ESL) – 3.1 (RSL)* = - 0.8 (b) : -4.2 (MS-CC) + (CC UL) = - 1.1 to -2.0

GPS Station: P058 = - 1.1 ± 0.5

*Inferred from NHE analysis: *(NS-CC) – (MRS-CC) = 0.9 – 1.2 mm/yr less subsidence per year between NS & MRS

Compare GPS data and Uplift Inferred from Sea Level Obs. mm/yr

Crescent City: 2.5 mm/yr uplift = + 12.5 cm (5 in) / 50years

Mad River Slough/ Arcata: 1 mm/yr subsidence = - 5 cm (- 2 in) / 50years

North Spit: 2 mm/yr subsidence = - 10 cm (- 4 in) / 50years

South Bay / Table Bluff: 2.7 mm/yr subsidence = - 13.5 cm (- 5.3 in) / 50years

Estimates of Secular Land Level Change

Crescent City: 2.5 mm/yr uplift = + 12.5 cm (+ 4.9 in) / 50 yrs2.3 mm/yr ESLR = + 11.5 cm (+ 4.5 in) / 50 yrs

RSL Change (- 0.2 mm/yr)= - 1 cm (- 0.4 in) / 50 yrs

Mad River Slough/ Arcata: 1 mm/yr subsidence = - 5 cm (- 2 in) / 50yrs2.3 mm/yr ESLR = + 11.5 cm (+ 4.5 in) / 50 yrs

RSL Change (3.3 mm/yr) = + 16.5 cm (+ 6.5 in) / 50 yrs

North Spit: 2 mm/yr subsidence = - 10 cm (- 4 in) / 50yrs2.3 mm/yr ESLR = + 11.5 cm (+ 4.5 in) / 50 yrs

RSL Change (4.3 mm/yr) = + 21.5 cm (+ 8.5 in) / 50 yrs

South Bay – Bear River: 2.7 mm/yr subsidence = - 13.5 cm (- 5.3 in) / 50yrs2.3 mm/yr ESLR = + 11.5 cm (+ 4.5 in) / 50 yrs

RSL Change (5 mm/yr) = + 25 cm (+ 9.8 in) / 50 yrs

Estimates of Relative Sea Level Change

+ 20

Ocean Surveys 1. Deploy temporary tide gages at available historic tide gage locations 1) Tie temporary gage to tidal bench mark

2) Analyze 30 yr record of sea level risea) Humboldt Bay (6-9)b) Trinidad

2. Install and maintain tide gages and tidal bench marks 1) Densify regional sea level observations

a) Trinidad Harbor & Shelter Coveb) Humboldt Bay (3) , Eel River Delta, Klamath River

2) Co-locate CGPS where/when possible. 3. Upgrade water depth sensors in the Central and Northern California Ocean Observing System (CeNCOOS)

1) Deploy stationary vented water depth sensors with external data loggers.a) Humboldt Bay (5)

Land Surveys 1. Tie 1931, 1944, & 1967 level surveys to 1988 where possible; including tidal bench

marks.

2. GPS survey subset of regional benchmarks to extend historic analysis to present day, and provide backbone of control to monitor on semi-annual basis. (Tidal bench marks and NAVD88 control)

3. Establish and monitor GPS-based level lines across Quaternary thrust faults utilizing both old & new control.

a) Little Salmon fault b) Mad River fault zone

4. Submit data to NGS for ‘blue booking’ to update survey control database (public). Expert contractor

5. Re-level selected NAVD88 level lines (most expensive).

GPS Height Modernization Program – Monitoring with CGPS as Reference

1. Collect and process GPS observations in accordance to NGS StandardsEquipment: CalTrans, NGS, & HSU

2. Maintain coordinates through repeated GPS surveys to update changes due to secular tectonic movement at both vertical and horizontal control.Contracted processing facility

3. Incorporate gravity observations to improve local geoid USGS Menlo Park or Penn State Univ.

Data processing/archiving/dissemination/modeling

1. Analyze vertical rates of land level changes (1931, 1944, 1967, 1988, present).

2. Identify expert to ‘Blue Book’ new level data – submit to NGS to publish updates in NGS database.

3. Process all available regional GPS observations 1993-present.

4. Bring new tide gage and CGPS data online for daily downloads and real time data stream.

5. Model observed vertical uplift rates with subduction zone model.

6. Enduser Modeling; e.g. eel grass and mariculture habitat changes change due to tectonic uplift/subsidence.

Near Term Tasks To Strengthen Plan / Assessment

1. Request 2010 tide gage data from USACE.

2. Request all historic level surveys from the NGS.

3. Prioritize historic temporary tide gages based on length of original records.

4. Assess available CENCOOS and HBNWR water level data.

5. Assess short tie level surveys needed between historic survey lines.

Near Platinum, AK.