Erosion Rates

1. Erosion Rates • Two axial surveys this year (March and June). Intensive survey planned for September 2005. • VIMS 2004 data delivered. Much analysis remains. • We are missing the 2004 Gust chamber results.

2. Field work to date: Six seasonal axial surveys completed so far (out of 8 total). 13 stations, spaced from 12 km downstream of Rt 301 bridge to 10 km downstream of fall line. Observations include CTD, LISST, ADCP, OBS, TSS, absorbance/transmittance and VSF (volume scattering sensor). 2. August 2004 intensive study of upper Potomac completed (2nd planned for September 2005 further downstream near ETM). Observations include erosion experiments using Gust microcosm and VIMS annular flume, CTD mooring, Owen tube particle settling velocity, pumped sample laboratory grain size analysis, and along- and across-channel tidal cycle survey with CTD, LISST, ADCP, TSS & OBS. Also bed sampling at 13 axial stations for profiles of grain size, water content, Eh, % organic, and micro-chirp acoustic response.

3. 2005 intensive 2004 intensive Example along-channel water column data (Sandford group). Each plot shows salinity in 1 ppt contour intervals starting at 1 ppt. Data from CTD, OBS and LISST as a function of distance downstream from fall line. Region of 2004 and 2005 intensives shown on upper left plot.

4. SUSPENDED PARTICLE SIZE VERSUS CONCENTRATION LISST D50 (microns) OBS Concentration (mg/liter) Example particle size vs. concentration data (Friedrichs group). LISST shows at least two distinct particle populations: larger particles form a significant component of the suspended particle population at lower concentrations, whereas relatively smaller particles dominate at higher concentrations. Data from upper Potomac, August 26, 2004.

5. SEDFLUME • One season of work in upper Potomac River • Designed to measure erosion under conditions of high shear stress (e.g. storms) • Data analyzed, report expected.

6. Light Attenuation • Funding thanks to Baltimore District, USACE • Two 2005 surveys, May and June. At least one more in Sept. • Data analyzed for color, turbidity, absorption, scattering

7. Updated Particulate Absorption and Scattering Sediment & Detrital Absorption Scattering Coefficient

8. AOP’s Depend on IOP’s • Consider Model based on Kirk (1984) Depends on latitude, date, time of day Depends on optical depth in the water column, and angular distribution of scattering µ0= cosine of in-water zenith angle a = absorption coefficient b = scattering coefficient  = wavelength

9. Modeling Plankton Controls on Suspended Sediment • In brief, we have completed the bulk of the analysis of VFX and monitoring data in the mainstem Bay to develop statistical relationships: (1) between chlorophyll and sediment sinking, (2) between environmental variables (T, Sal, nutrients) and chl-a sinking, (3) between Kd and chl-a and TSS. These analyses provide clear evidence for and significant functions quantifying planktonic control of TSS sinking. These analyses also clearly show how TSS and chl-a interact to control Kd in ways differ from conventional views.

10. Modeling Plankton Controls on Suspended Sediment • We are in the middle of our mesocosm experiments in which we are trying to quantitatively test for nutrient controls on TSS and chl-a sinking (and suspension). Initial results are very interesting showing, for example, that clay particles tend to stay in suspension without the addition of nutrients. These experiments have been delayed because of unanticipated logistical problems in starting up the mesocosm facility. We will, however, extend the experimental period into the fall to finish up studies that were not completed in spring 2005.

11. Modeling Plankton Controls on Suspended Sediment • We plan to transfer this information to you in the winter and spring of 2006, and continue to analyzed results toward publication. We will be also be working with you to incorporate these algorithms into model code, using our Stella models as a testing platform. You and I will need to discuss the details of how you want to proceed on this front.

12. Estuarine Phosphorus Model • Contracted by MWCOG to LTI and Horn Point. • Field work underway by Jeff Cornwell • Review and model conceptualization underway by LTI

13. Hydrodynamic Model • Grid completed. • Running for years 1993 – 1999 with inputs from Phase V Watershed Model. • Coupled to water quality model. Results under examination

14. Surface Waves • Model selected and implemented • Forwarded to VIMS for incorporation into boundary layer model

15. Bank Loads • Jeff Halka funded by MDE for Maryland portion of bay. • A simplified approach based on existing info will be adopted for Virginia. • Behind schedule but no major problem

16. CE-QUAL-ICM • Coupling to CH3D achieved • Results available for 1993 – 1994. Presently undergoing evaluation

17. pH Alkalinity • No activity • No funding identified • Substantial field work conducted in 2004 by Boynton and Cornwell for ICPRB, MWCOG • Completion of work in this area by 2007 is unlikely

18. Algal Speciation • No activity • No funding identified • Completion of work in this area by 2007 is unlikely

19. Scheduling Concerns/Deadlines • Year 1 sediment erosion results from Gust chamber – October 05 • Phase 5 Watershed Model flows for year 2000 – October 05 • Phase 5 Watershed Model loads for years 1995-2000 – October 05 • Potomac River Sediment Oxygen Nutrient Exchange – January 06

20. Scheduling Concerns/Deadlines • Bank Loads – January or September 2006 • EPA GIS work by January? • Shoreline armoring not until available until September • Funding Gap – Available funds exhausted in October. When is next funding event?