CMS Modeling of the North Coast of Puerto Rico PRESENTED BY: Dr. Kelly Rankin Legault, Ph.D., P.E. 1 Dr. Alfredo Torruella, Ph.D. 2 1 USACE Jacksonville District 2 University of Puerto Rico October 2016 Trusted Partners Delivering Value Today for a Better Tomorrow US Army Corps of Engineers
Beach Erosion in Puerto Rico PROBLEMS Erosion, storm surge (inundation) and wave attack Damage to coastal structures and infrastructure Loss of natural coastal habitat (beach, dunes, reef) Threatened recreational and tourism opportunities OPPORTUNITIES Reduce storm damage to coastal structures and infrastructure Protect the hurricane evacuation route capability Restore dunes to function naturally Protect natural habitat Improve community resilience Maintain recreation and tourism opportunities Trusted Partners Delivering Value Today for a Better Tomorrow 2 2
USACE RSM Program Trusted Partners Delivering Value Today for a Better Tomorrow 3
Wave Climate San Juan Region CariCOOS San Juan buoy wave data Trusted Partners Delivering Value Today for a Better Tomorrow 4
CariCoos San Juan Buoy Wave Data Significant Wave Height Mean Wave Direction Peak Wave Period 5
CariCoos San Juan Buoy Wind Data Trusted Partners Delivering Value Today for a Better Tomorrow
Wave and Wind Climate Summary Bi-modal wave climate: larger, longer period swell in winter, mostly from the northeast, but with some forcing from the west Smaller, shorter period wind waves in summer, with a more easterly component Bi-modal wind climate: Fairly consistent east-northeast trade winds Weaker more southerly winds in fall Net Result: winter regime wave dominated (more northerly forcing) summer regime wind dominated (more easterly forcing) Trusted Partners Delivering Value Today for a Better Tomorrow
North Coast Morphology The beaches of San Juan are Headland-Bay beaches Headland-Bay beaches occur in coastal systems with a limited sand supply Trusted Partners Delivering Value Today for a Better Tomorrow
North Coast Morphology Wave diffraction plays a key role in the dynamics of Headland-Bay beaches The curved wave fronts lead to a stable beach that does not require a continuous sand supply in the alongshore Trusted Partners Delivering Value Today for a Better Tomorrow
North Coast Morphology A second defining characteristic of the beaches of San Juan is the presence of fringing reefs Trusted Partners Delivering Value Today for a Better Tomorrow
North Coast Morphology On the positive side, the fringing reefs dissipate the majority of large wave energy, protecting the beaches (86% - 92% wave energy reduction during Hurricane Irene, as per R. Calzada s Masters Thesis)
North Coast Morphology On the negative side, the fringing reefs generate strong currents and infra-gravity waves during swell events that may contribute to long term sand loss from the system Current speed m/s Currents 18 March 2008 Trusted Partners Delivering Value Today for a Better Tomorrow
Coastal Modeling System (CMS) Flow and Wave
Coastal Modeling System (CMS) Flow and Wave Bathymetry (2008 NOAA DEM, Local Surveys)
Coastal Modeling System (CMS) Waves and Current Measurements
Calibration Feb 2015 WWIII waves and San Juan Tide Forcing Depth (m) Depth (m) Tide (m) 12.1 12 11.9 11.8 11.7 AWAC106_outside 11.6 San Juan Bay NOAA gauge 11.5 AWAC106_outside_modeled 11.4 11.3 1/26/15 0:00 1/31/15 0:00 2/5/15 0:00 2/10/15 0:00 2/15/15 0:00 2/20/15 0:00 2/25/15 0:00 3/2/15 0:00 3/7/15 0:00 Time Tide (m) 7.3 AWAC102_inside 7.2 AWAC102_inside_modeled 7.1 7 6.9 6.8 6.7 6.6 6.5 6.4 1/26/15 0:00 2/5/15 0:00 2/15/15 0:00 2/25/15 0:00 3/7/15 0:00 3/17/15 0:00 3/27/15 0:00
Calibration Feb 2015 WWIII waves and San Juan Tide Forcing Significant Wave Height 4 3.5 3 Hs (m) 2.5 2 1.5 1 0.5 0 1/26/15 0:00 2/5/15 0:00 2/15/15 0:00 2/25/15 0:00 3/7/15 0:00 3/17/15 0:00 3/27/15 0:00 AWAC106_outside Model Significant Wave Height Hs (m) 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 1/26/15 0:00 2/5/15 0:00 2/15/15 0:00 2/25/15 0:00 3/7/15 0:00 3/17/15 0:00 3/27/15 0:00 Time AWAC102_inside Model
Calibration Feb 2015 WWIII waves and San Juan Tide Forcing 0.25 Depth Averaged Speed 0.2 Spd (m/s) 0.15 0.1 0.05 AWAC102_inside_curr_spd Model_curr_speed 0 2/5/15 0:00 2/10/15 0:00 2/15/15 0:00 2/20/15 0:00 2/25/15 0:00 Time 3/2/15 0:00 3/7/15 0:00 3/12/15 0:00 Depth Averaged Speed Spd (m/s) 0.2 350 0.15 300 0.1 250 0.05 200 0 150-0.05 100-0.1 50-0.15 0 2/5/15 0:00 2/10/15 0:00 2/15/15 0:00 2/20/15 0:00 2/25/15 0:00 3/2/15 0:00 3/7/15 0:00 3/12/15 0:00 Time AWAC102_inside_Veast AWAC102_inside_Vnorth AWAC102_inside_curr_dir
Model Run WWIII forcing 6 months 6 Sig Wave Height and Peak Spectral Period 25 Hs (m) 5 4 3 2 1 20 15 10 5 Tp (s) Hs (m) Tp (s) 0 0 6/22/2004 12/19/2004 6/17/2005 12/14/2005 6/12/2006 12/9/2006 6/7/2007 12/4/2007 6/1/2008 11/28/2008 5/27/2009 11/23/2009 6 5 Sig Wave Height and Ursell Parameter 300 250 Hs (m) Hs (m) 4 3 2 1 50 0 0 6/22/2004 12/19/2004 6/17/2005 12/14/2005 6/12/2006 12/9/2006 6/7/2007 12/4/2007 6/1/2008 11/28/2008 5/27/2009 11/23/2009 200 150 100 Ursell P Ursell Ursell 30d Window
Mean Nearshore Currents del wse (m) wse nearshore and Hs 0.35 6 5 0.25 4 0.15 3 2 0.05 1-0.05 0 12/24/2007 1/13/2008 2/2/2008 2/22/2008 3/13/2008 4/2/2008 4/22/2008 5/12/2008 6/1/2008 6/21/2008 date Hs (m) del wse Hs Vy (m/s) Hs and Vy 0.7 6 0.5 5 4 0.3 3 0.1 2 1-0.1 0 12/24/2007 1/13/2008 2/2/2008 2/22/2008 3/13/2008 4/2/2008 4/22/2008 5/12/2008 6/1/2008 6/21/2008 date Hs (m) PT4 Vy Hs
Mean Crosshore Currents
Mean Nearshore Currents
Mean Crosshore Currents
Mean Onshore Currents
Mean Offshore Currents
Coastal Modeling System (CMS) Flow and Wave Incident Wave Energy and Coastal Currents CMS is likely to be an appropriate model to simulate the nearshore system METHODOLOGY Strength of coastal currents are strongly correlated with incoming wave energy Examine offshore flows and low frequency wse in the nearshore Examine distribution and volume of sediments in the nearshore, mass flux of sediments being driven offshore. Vy (offshore) (m/s) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0-0.1 Vy vs. Hs -0.2 0 1 2 3 4 5 6 Hs (m)
Conclusions Strength of coastal currents are strongly correlated with incoming wave energy The beaches of San Juan are Headland-Bay beaches, a sign of a sand starved system. The beaches of San Juan are in short term and medium term equilibrium. The long term beach erosion is likely due to sand being pumped out of the system through the reef passes during swell events, possibly exacerbated by infra-gravity waves. More research is needed (and is in the pipeline!) to determine the thickness of the sand layer in the bays, as well as the dynamics of the sediment throughout the year.