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SDAG Monthly Meeting
Wednesday, March 18, 2015

Location: Emiliano's Mexican Restaurant
6690 Mission Gorge Road,San Diego, CA 92120
(619) 284-2460

Directions: On Mission Gorge Road overlooking Admiral Baker golf course. You will probably have to drive about 1/2 mile past the restaurant and make a U-turn to get into the parking lot.
happy hour
5:30pm -
Social hour  
6:30pm -

Menu: Mexicano Fantastico, Cash Bar

Cost: $30.00 for non-members, $25.00 for members, $15.00 for students if pre-registered by the deadline, $5 extra if you did not make a reservation. Click the SDAG member checkbox on the reservation form if you are a member.

Reservations: Make your reservation online by clicking the button below no later than NOON, Monday, March 16th. RESERVATIONS CANNOT BE ACCEPTED AFTER Monday at noon. Late reservations/cancellations are preferred over walk-ins or no-shows. Fees payable at the meeting or pre-pay with PayPal.
As a new payment option, there will be a phone credit card reader at the meeting.

If you are a current SDAG member and are not getting e-mail announcements,
make sure the SDAG secretary has your correct e-mail address.

7:30pm -

Speaker 1: Tyler Barnes - Undergraduate Environmental Studies, University of San Diego
SDAG 2014 Scholarship Recipient


Abstract: Land-based sedimentation and turbidity contributes to declining coral reef conditions in the US Virgin Islands. Not only does turbidity smother corals, but also blocks light, which interferes with the ability of zooxanthellae to photosynthesize. Unpaved roads and other watershed development activities increase runoff volumes to near-shore marine systems, often resulting in increased turbidity. Residents of Coral Bay, St. John, USVI are concerned with the impact of local development on turbidity, but are unsure how to monitor turbidity effectively. The objectives of this study were: 1) to determine the appropriate frequency of sampling to capture turbidity variation, and 2) to describe what factors influence nearshore and offshore turbidity in Coral Bay, St. John, USVI. At a nearshore and an offshore site within Coral Bay, St. John, USVI, turbidity was monitored at a monthly frequency by measuring water sample total suspended solids (mg/L) and at a ten- minute frequency by measuring the backscatter of light using nephelometers (NTU). A simulated storm experiment was conducted to produce a calibration between the two measurement techniques and test the duration of turbidity plumes. Turbidity was found to be highly variable and turbidity plumes relatively short- lived (minutes- hours). However, the monthly sampling did not capture the natural variation. Therefore, high frequency sampling (minutes) is necessary to properly monitor turbidity variation in Coral Bay. Regional wave height, used as a proxy for hydraulic energy in the bay, and rainfall data were collected to investigate factors that influence turbidity. Regression analysis showed a correlation between regional wave height and turbidity, suggesting that energy influences turbidity variation. Though particularly high rainfall events may result in high turbidity at the nearshore location, there was no correlation between rainfall and turbidity. However, the terrigenous composition of both nearshore and offshore suspended solids suggests that rainfall introduces land-derived sediment into the system but that waves re-suspend sediment from the seafloor and produce turbidity plumes. Thus, proper land-use planning, aimed at reducing runoff volumes, may decrease turbidity.

As a San Diego native, Tyler grew up fascinated by the workings of the natural world, particularly coastal environments where he spent most of his summers. Tyler enjoyed an interdisciplinary education in environmental studies at the University of San Diego, where he soon met Dr. Sarah Gray and became involved in her US Virgin Islands sedimentology research. While working in Dr. Gray's lab, Tyler has enjoyed not only the fieldwork that included scuba diving in the Caribbean, but also the satisfaction of communicating findings with peers. He looks forward to continuing his education and research in marine geology, hopefully beginning his graduate studies this fall.

Speaker 2: Dr. David Cruden - Emeritus Professor, Civil & Environmental Engineering and Earth and Atmospheric Sciences University of Alberta, Canada


Abstract: An essential input to any calculation of the stability of a natural slope is a hypothesis about how the slope may move. No formal method for estimating likely kinematic modes of slopes exists unless the slope is currently moving or has moved in the past. A working hypothesis is that similar slopes in similar materials move in similar modes in response to similar causes.

During the IDNDR (1990-2000), the IAEG Commission on Landslides contributed to the Working Classification which records an international consensus on types of landslides. A landslide can be typed by a term describing the natural materials before they were displaced and a second term describing the movement. Materials are rock, debris or earth; earth may be sand, silt or clay. Movements may be falls, flows, slides, spreads or topples. Water conditions in the displaced material may range from dry thru' moist and wet to very wet. In permafrost terrain, frozen and thawed displaced material may occur. Water conditions, material and mode of movement may govern the rate of movement of the displacing mass. It can range from extremely slow to the extremely rapid movements which may have catastrophic impacts.

Activity, its distribution and style may affect anticipated modes of movement in assessed slopes. Slopes may be active suspended, reactivated, dormant, abandoned, stabilized, repaired, or relict. Styles of movement may be complex, composite, successive and multiple. Compilations of the historic activity of similar slopes as landslide inventories suggest hazard scenarios which can form plausible initial hypotheses for risk assessments.

Dr. David Cruden, Emeritus Professor of Civil & Environmental Engineering and of Earth and Atmospheric Sciences at the University of Alberta, Canada, is a recent Varnes medalist of the International Consortium on Landslides, a Legget medalist of the Canadian Geotechnical Society and a Julian Smith medalist of the Engineering Institute of Canada for his contributions to landslide studies. During the International Decade for Natural Disaster Reduction (1990-2000), he led the collaboration of the International Geotechnical Societies that produced the Working Classification of Landslides for the International Union of Geological Sciences. He chaired IAEG's Commission on Landslides from 1988 to 1995. He has published textbooks on engineering geology and terrain analysis along with three hundred technical papers. He was an Associate Editor of the Canadian Geotechnical Journal for 20 years & is presently an Advisor to the Editorial Board of "Landslides". He continues to suggest extensions to the Working Classification of Landslides.

Upcoming SDAG meetings - 2015

March 18: Student Presentations

April 15: Student Presentations - part 2

TUESDAY May 12: Monte Marshall - Geology of the Polynesian Islands

MONDAY June 1: Eric Drummond - Ice Cold Gold - Joint SDAG/SCGS Meeting

Meetings are usually scheduled for the 3rd Wednesday evening of the month. Meeting information on this website is normally updated the second week of the month.

If you have any information, announcements, ads or suggestions for an upcoming newsletter, please submit it to Rupert Adams, (2015 SDAG Secretary). Any news regarding upcoming events that may be of interest to the Association or news of your business can be submitted. The submittal deadline for the next SDAG newsletter is the last Friday of the month.
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