Further Development of Chesapeake Bay Estuarine Model Focusing on Sediment Transport and SAV Simulation

Transcription

1 Further Development of Chesapeake Bay Estuarine Model Focusing on Sediment Transport and SAV Simulation Modeling Subcommittee Quarterly Review July 8, 2009 Ping Wang &/for Anonymous Friend

2 Overview: 13K WQM (Water Quality Model) developed in 2002-?-2004, simulates nutrient cycles and the responses of algae, DO, SAV, etc. But only one class of sediment was simulated, without real simulation of re-suspension from bed. Hydrology period for calibration: K WQSTM (Water Quality & Sediment Transport Model), has been developing since Purpose: to better/fully simulate sediment transport and SAV responses. Hydrology period for calibration:

3 13k WQM 57K WQSTM Two grid

4 Development of Sediment Transport Module for WQSTM by ERDC: ROMS or SedZL-J. Sediment classes -- 3, 4. Size ranges and settling rates for each classes. Uniformed settling rate or variable rates to meet calibration. Tried various critical shear stress for erosions., besides excellent work on Chl-a, DO, etc, simulations.

5 Existing (apparent) Problems Sediment Transport: Sands: are almost negative. Age: an upper layer is older than a lower layer. SAV simulation: Not calibrate well Response in E3 cannot reach the goal.

6 Clay Silt Sand Fine Clay

7 Clay Silt Sand Fine clay

8 Clay Silt Sand -10 Fine Clay -15

9 From a USGS web

10 ROMS sediment transport module 7 bed layers. Settling velocities for sediment classes: Clay Slit Sand Fine-clay run2xx & up run xx SC Kim,May/ New test

11 Besides implementing ICM code, also Implement ROMS code: 1) Correct the errors in layer transfer that causes errors in changes of thickness and ages. 2) Adding crit_d (critical shear stress for deposition), besides crit_e (for erosion) Initial ROMS Modified > Crit_e, then erode ح erode, Crit_e <ح then crit_d < ح <crit_e < crit_d, then depo ح depo crit_e, then >ح

12 Proposed work Fix the problem of negative sediments. Compliance with the principal of mass balance. Reasonable bed distributions: 1) The ages should be older in the lower layer. Relate the ages to critical shear stress of erosion. crit_e* = f(crit_e, age) Sand or bedrock armors. 2) Consistency among shear stress distribution and bed components. Reasonable TSS in water columns, ETM. Examine with key axial profiles. SAV?

13 Cell A Cell B MassA MassB InA outa InB time steps 1 and 2 MassA2 =MassA1 +ina-outa MassB2 =MassB1 +inb-outb If out > In+Mass1, Mass2 < 0. A) If mass2<0, then mass2=0. B) Never allow out>in+mass1.

14 Hour counts for 4 ranges of shear stress in a year for individual cells (Total 365*24=8760 hours) Cell <Clay >=Clay <Silt >=Silt <Sand => Sand A 8760 B 8760 C D E

15 From a USGS web

16 Proposed Work: Fix the problem of negative sediments. Compliance with the principal of mass balance. (To better simulate sediment transport) Reasonable bed distributions: 1) The ages should be older in the lower layer. Relate the ages to critical shear stress of erosion. crit_e* = f(crit_e, age) Sand or bedrock armors. 2) Consistency among shear stress distribution and bed components. Reasonable TSS in water columns, ETM. Examine with key axial profiles. (To better estimate water clarity and SAV) SAV?

17 Existing (apparent) Problems Sediment Transport: Sand: almost are negative. Age: an upper layer is older than a lower layer. SAV simulation: Not calibrate well. Response in E3 cannot reach the goal.

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20 From Cerco (xxxx)? clay,silt,sand

21 Plans On sediment transport: (before the next subcommittee meeting, and before the EOY): Correcting the existing errors such as significant negative values, and making consistency among bed layer transformations and shear fields. Improving water column TSS calibrations. Extending simulation to to compare shallow water TSS and Ke. Data correction for Ke. Transferring info for SAV simulations. SAV?

22 Get feedback from the audiences: Do we need to further work on sediment transport? i.e., does the current model meet the specification/expectation of sediment transport? Ranges of critical shear stress for erosion and deposition? Erosion rates? Ranges of settling velocity of the 4 components? Variable settling velocity or uniformed? Initial bed components? Thickness? Observations with split TSS components?