improved storm surge model prediction using a high resolution unstructured grid

Improved Storm Surge Model Improved Storm Surge Model Prediction Using a High Resolution Prediction Using a High Resolution

Unstructured Grid Unstructured Grid

Jian ShenJian ShenVirginia Institute of Marine SciencesVirginia Institute of Marine Sciences

College of William and MaryCollege of William and Mary

Unstructured 3D Model (UnTRIM)Unstructured 3D Model (UnTRIM)

• “UnTRIM” incorporates an Unstructured grid into TRIM model (Tidal, Residual, Intertidal Mudflat), originally developed by Vincenzo Casulli

• It simulates three-dimensional hydrodynamic and transport processes

• It uses an orthogonal unstructured grid• It conserves mass locally as well as globally • It uses Eulerian-Langangian transport scheme • It employs semi-implicit finite difference and finite

volume method- very efficient computationally• It is capable of simulating wet-dry processes

OrthogonalOrthogonal Grid Structure Grid Structure

• Use polygons to represent a prototype estuary (3-, 4-, 5-sides)

• Better fitting complicated geometry in estuarine and coastal environment

• Using orthogonal grid simplifies the numerical algorithm

Grid StructureGrid Structure

Water depth

Isabel Simulation StudiesIsabel Simulation Studies

• Study the accuracy of model prediction of Isabel forced by a stationary, circular wind model

• Compare model prediction with and without simulating inundation

• Study influence of open boundary condition specification on surge simulation– still boundary condition vs. inverse pressure adjust

boundary condition •

Model GridsModel Grids

Surface element =121338

Surface element =239541

Grid layout at York and James RiversGrid layout at York and James Rivers

Gloucester Pt.

0 2 km

0 2 km

Model CalibrationModel Calibration

• Calibrate model for tide

forced by 9 tidal constituents M2, S2, K1, O1, Q1, K2, N2, M4, and M6

• Model was run for 3 months and the results of the last 29 days were used for computing tidal harmonics

• Timestep = 5 min.•

Tidal Simulation (MTidal Simulation (M22 tide) tide)

Tidal Simulation (KTidal Simulation (K11))

Observation StationsObservation Stations

Tidal Constituents Comparison Tidal Constituents Comparison (Amplitude)(Amplitude)

Amplitude is in mObservations are based on 1992 data

ModeledObs. ModeledObs. ModeledObs. ModeledObs. ModeledObs. ModeledObs.Stations

Bay Bridge 0.38 0.37 0.06 0.07 0.09 0.09 0.07 0.06 0.05 0.05 0.01 0.02Kiptopeke 0.38 0.37 0.06 0.07 0.08 0.09 0.07 0.06 0.05 0.05 0.01 0.02Sewells Pt. 0.35 0.35 0.06 0.06 0.08 0.08 0.06 0.06 0.05 0.04 0.01 0.02

Gloucester Pt. 0.34 0.33 0.05 0.06 0.07 0.08 0.05 0.05 0.04 0.04 0.01 0.02W indmill Point 0.17 0.16 0.03 0.03 0.04 0.04 0.04 0.03 0.02 0.02 0.01 0.01Lewisetta 0.18 0.17 0.04 0.03 0.04 0.04 0.03 0.02 0.02 0.02 0.02 0.01Solomons Isaland 0.17 0.16 0.03 0.02 0.03 0.04 0.04 0.03 0.03 0.02 0.02 0.01Cambridge 0.24 0.22 0.04 0.03 0.05 0.05 0.06 0.05 0.05 0.04 0.03 0.01Annapolis 0.12 0.13 0.02 0.02 0.03 0.03 0.06 0.06 0.05 0.04 0.01 0.01Baltimore 0.16 0.14 0.03 0.02 0.04 0.03 0.07 0.07 0.06 0.05 0.02 0.01Tolchester Beach 0.18 0.16 0.04 0.02 0.04 0.04 0.08 0.07 0.06 0.05 0.02 0.01

O1 K2M2 S2 N2 K1

Tidal Constituents Comparison (phase)Tidal Constituents Comparison (phase)

ModeledObs. ModeledObs. ModeledObs. ModeledObs. ModeledObs. ModeledObs.

Bay Bridge 99.5 99.5 75.1 75.1 39.4 39.4 199.3 199.3 268.3 268.3 224.7 224.7Kiptopeke 112.0 110.4 79.6 85.6 51.1 49.6 206.4 207.0 275.0 273.7 193.4 235.4Sewells Pt. 122.7 125.4 93.1 101.1 62.8 66.2 211.5 213.4 279.4 281.6 194.6 252.4Gloucester Pt. 130.6 131.9 101.8 105.6 71.3 72.8 215.4 211.3 283.0 281.4 163.3 259.3W indmill Point 181.9 196.4 152.8 166.9 119.1 130.9 241.7 242.9 312.7 313.5 298.9 15.6Lewisetta 254.0 253.9 203.8 231.0 185.6 189.0 289.0 288.3 360.7 355.4 324.8 18.5Solomons Isaland 270.9 276.5 211.9 254.3 202.7 210.2 319.0 329.1 24.4 27.4 325.1 43.8Cambridge 320.7 336.3 257.5 311.1 255.9 271.6 341.3 355.3 40.4 46.8 352.8 105.9Annapolis 7.1 8.8 319.6 348.0 300.8 305.9 0.9 10.1 56.3 65.2 58.9 133.0Baltimore 56.1 53.9 4.9 37.4 345.4 348.3 14.1 20.8 67.6 75.1 120.0 173.9Tolchester Beach 59.8 64.3 3.4 36.9 348.0 356.6 12.4 18.3 65.8 72.3 120.0 184.2

M2 S2Station N2 K1 O1 K2

Phase is in degree

Isabel Simulation ResultsIsabel Simulation Results

Comparison of Model ResultsComparison of Model Results(with and without inundation)(with and without inundation)

G loucester Point (with flooding)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeledPredicted (HAM )O bserved

Sewells Point (without flooding)

-0.5

0

0.5

1

1.5

2

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeledPrediced (HAM )O bserved

Sewells Point (with flooding)

-0.5

0

0.5

1

1.5

2

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

Modeled

Sweells Hall (HAM)

Observed

Gloucester Point (without flooding)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vatio

n (m

)

ModeledPredicted (HAM)Observed

Comparison of Model ResultsComparison of Model Results(with and without inundation)(with and without inundation)

Baltimore (with flood)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeled Prediced (HAM )O bserved

Baltimore (without flood)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeledPredicted (HAM )O bserved

Colonial Beach (with flood)

-0.5

0

0.5

1

1.5

2

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeledPredicted (HAM )

Observed

Colonial Beach (without flood)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeledPredicted (HAM )Observed

Influence of Open Boundary ConditionInfluence of Open Boundary Condition

G loucester Point (with flooding)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

M odeledM odeled (IPABC)O bserved

Sewells Point (with flooding)

-0.5

0

0.5

1

1.5

2

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

Modeled

Modeled (IPABC)

Observed

Inverse Pressure Adjustment

Comparison with ADCIRC• UnTrim

– With inverse pressure adjustment

– Timestep =5 minutes

• ADCIRC– Without inverse pressure adjustment

– Timestep =5 sec

Gloucester Point (with flooding)

-0.5

0

0.5

1

1.5

2

2.5

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

ADCIRC UnTRIM

Observed

Comparison with ADCIRC

Swelles Hall (with flooding)

-0.5

0

0.5

1

1.5

2

0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72

Hour (from 9/17/2003 0:00)

Ele

vati

on

(m

)

ADCIRC UnTRIM

Observed

ConclusionsConclusions

• Grid resolution is crucial for accurately simulating surge and inundation

• Wind filed is critical in accurately simulation storm surge

• Unstructured model is a robust tool for simulating tide and storm surge