Folly Beach 1-yr Post-Construction Monitoring Report Nicole Elko, Ph.D. September 8, 2015

Purpose Monitor sediment placed during 2014 federal renourishment –Planning, budgeting, and design Life-cycle analysis –How long will the project last? Meet USACE requirements

USACE CONTRACT Great Lakes Dredge & Dock 1.4 M cy sand $30.7 M (15% City cost) January – June 2014 MONITORING August 2014 June Federal Project recap

OCRM Monuments

Beach Nourishment Performance Evaluation “periodic nourishment will be initiated upon a mutual agreement between the Government and the Local Sponsor based on the results of annual inspections and surveys. Periodic nourishment is deemed necessary when 25% of the length of the project storm berm has reached a 15 foot width at elevation 9.0 NGVD. At this time an approximate high tide beach width of feet will exist.” 8.0 ft NAVD ft berm & MHW width 2.Volume remaining 1.8-ft berm & MHW width 2.Volume remaining PEL (Perpetual Easement Line)

200 ft wi -20 ft average +

65 ft wi -1.5 ft tapers 19% 5 of 26 profiles = 19%

Life Cycle Analysis 8-ft berm & MHW Shoreline Length # of Monuments Shoreline length/# of Monuments required to meet trigger 5798ft7monuments # of years until trigger is met4yrs3 Year trigger will be met: Rudimentary – based on only 2 points

SW -15 to -30 cy/ft

Volumetric Analysis Total volume placed by 2014 project (cy) 1,400,000 Total volume in place: Aug 2014 (cy)1,093,513 Volume change Aug June 2015 (cy)-334,862 Volume remaining in June 2015 (cy)758,652 Just over half of the placed volume remains

Life Cycle Analysis Volume trends 4yrs

Life Cycle Analysis Volume trends 3yrs

Life Cycle Analysis Volume trends 0yrs

Summary of Volume Trends If trends continue, performance may be better than 3-4 yrs predicted

Summary of Monitoring Between Aug 2014 & Jun 2015 –20 ft shoreline (MHW) erosion –“8-ft berm” eroded 1.5 ft –Lost cy/ft volume As of June 2015, on average, –beach is 200 ft wide –“8-ft berm” is 65 ft wide –~half nourishment volume remains USACE trigger –“8-ft berm” < 15ft at 5 of 26 profiles (19%) –Trigger will be met in 3 to 4 years ( )

Folly Beach 1-yr Post-Construction Monitoring Report Nicole Elko, Ph.D. September 8, 2015