COASTAL EVOLUTION AND CLIMATE CHANGE: CHALLENGES OF MULTI-SCALE SPATIAL AND TEMPORAL VARIABILITY

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1 COASTAL EVOLUTION AND CLIMATE CHANGE: CHALLENGES OF MULTI-SCALE SPATIAL AND TEMPORAL VARIABILITY Dr. Jennifer L. Miselis Naval Research Laboratory Stennis Space Center, MS 1

2 PRIMARY AGENTS OF COASTAL CHANGE 2 SEASONAL EVENTS (e.g. extratropical storms) EXTREME EVENTS (e.g. Floods, Tsunami, Hurricanes, also oceanic oscillations) Spatial Scale of Coastal Impact RELATIVE SEA LEVEL FLUCTUATIONS

3 SHORT-TERM COASTAL RESPONSE 3 Short-term changes (O~days) Extratropical storm in North Carolina, USA Data courtesy Jeff List, USGS Yearly-decadal changes Composite of short and event-related changes Data courtesy William Birkemeier, USACE

4 EXTREME EVENT-SCALE COASTAL RESPONSE 4 Changes due to extreme events Hurricanes Ivan and Katrina

5 LONG-TERM COASTAL RESPONSE 5 Adapted from Barras et al., 2003, USGS Open-File Report Changes due to relative sea level rise Southeastern coast of Louisiana

6 PRIMARY AGENTS OF COASTAL CHANGE 6 SEASONAL EVENTS (e.g. extratropical storms) CLIMATE CHANGE EXTREME EVENTS (e.g. Floods, Tsunami, Hurricanes, also oceanic oscillations) Spatial Scale of Coastal Impact RELATIVE SEA LEVEL FLUCTUATIONS

7 GLOBAL OCEANS AS A BATHTUB??? Present Conceptual Model Suggested Conceptual Model yrs?? present Long-term Processes LGM Mechanisms for sea level rise in IPCC models are 1) melting of land ice and 2) thermal expansion of sea water (Meehl et al., 2007 in IPCC Climate Change 2007). Waves Geology Recent work indicates that many of the processes involved in SLR are highly spatially variable (Milne et al., 2009; Mitrovica et al., 2009). Inundation forecasts completely ignore processes (i.e. hydrodynamics & sediment transport) that effect short-term coastal evolution despite profound near-term effects for coastal populations (Komar & Allan, 2007; Keim et al., 2004, Goldenberg et al., 2001). CHALLENGE: How do we reconcile longterm and short-term processes to improve predictions of sea level rise-related inundation? STEP ONE: Investigate the role of waves and geology in coastal evolution over a range of temporal and spatial scales.

8 MEASURING SHORELINE CHANGE 8 Land-based methods Lidar GPS-USGS Swash Buggy, Jeff List GPS-ATV Aerial Methods Aerial Photography

9 MEASURING SHORELINE CHANGE 9 LIDAR Light Detection and Ranging Dense topographic coverage Shallow bathymetric coverage in clear water

10 INVESTIGATING NEARSHORE GEOLOGY 10 Electric Vibracoring High-resolution sub-bottom profiling Integrated with RTK-GPS Interferometric Bathymetry Shallow-water Geophysics Sediment Sampling

11 NEARSHORE REMOTE SENSING 11 BASIR Courtesy Dr. Jesse McNinch, USACE Photogrammetry and Video Imaging Photo courtesy of Kate Brodie, VIMS Mobile X-band Radar

12 SPATIAL RELATIONSHIPS 12 East Coast of United States GEOLOGICAL INFLUENCES ON COASTAL BEHAVIOR VA NJ Nearshore and shelf morphology related to increased shoreline erosion (McNinch, 2004; Kelley et al., 2001; Miselis & McNinch, in prep.) Sediment characteristics effect wave propagation (Holland et al., 2009) FL Nearshore sediment availability related to decadal shoreline change (Miselis and McNinch, 2006)

13 NEARSHORE MORPHOLOGY & COASTAL CHANGE 13 SHORE-OBLIQUE BARS Found in discrete fields (lengths: km) Mapped in water depths of 2-15 m Location of shore-oblique bars Dimensions: km L x km W Relief from trough to crest: ~3 m Spatially associated with decadal shoreline change (McNinch, 2004) Bathymetric gradients Sediment transport gradients (Miselis & McNinch, in prep.) N Field of shoreoblique bars ~1 km

14 SHELF MORPHOLOGY AND COASTAL CHANGE 14 Coastal Virginia and inner shelf Sandbridge Shoal is major shelf feature in study area Little nearshore bathymetry, except shoreface-attached sand ridge to south Shoreline change signal influenced by simple nearshore bathymetry Sandbridge Shoal Figures from Kelley et al., 2001, MMS Report

15 SEDIMENT VARIABILITY AND COASTAL CHANGE 15 Santiago Buenos Aires Montevideo Porto Alegre Cassino Beach NRL Research Initiative to understand role of heterogeneous sediments in coastal dynamics Observed mud event at Cassino Beach, Brazil Wanted to understand how mud influenced waves Implications for shoreface profile evolution and shoreline change Photo courtesy Todd Holland, NRL

16 SEDIMENT VARIABILITY AND COASTAL CHANGE cm Observed attenuation of wave energy by mud Found mud at surface of cores, but also observed a fluid mud layer of variable thickness Photos courtesy Todd Holland, NRL Fluid mud layer is more viscous than water; difficult to incorporate into models of bottom-boundary layer dynamics

17 SEDIMENT AVAILABILITY AND COASTAL CHANGE 17 Region of volume & shoreline change comparison Adapted from Miselis & McNinch, in review, Marine Geology

18 SEDIMENT AVAILABILITY AND COASTAL CHANGE 17 Correlation coefficient = 0.58, significant at the 95% C.I. Nearshore Sediment Volume vs. Shoreline Change Region of volume & shoreline change comparison Shoreline change rate (m/yr) Volume (m 3 ) Northing (UTM, m) Miselis & McNinch, 2006 SLC Rate (smooth) Volume (R01) Adapted from Miselis & McNinch, in review, Marine Geology Volume of sediment available for transport

19 APPLICATIONS FOR COASTAL ARGENTINA 18 If we want to predict the effects of sea level rise, such as: Coastal response to larger/more frequent storms Inundation vulnerability/coastal erosion Sediment transport We need to ask: 1) Where does morphology refract waves and focus energy on coast? 2) Does variability in shoreface slope, which may be a function of the character of the subsurface geology, affect extent of inundation? 3) Is there a link between offshore/shoreface sediment availability and coastal response to climate change? 4) Does variability in alongshore sediment type affect wave characteristics? How will sea level rise change these interactions?

20 SUMMARY 19 The effect of climate change on short-term processes (e.g. increases in storm frequency and intensity) may be more profound for coastal populations. Short-term coastal evolution is mediated by the interplay between hydrodynamics, nearshore and shelf morphology AND geology. Spatial variability in coastal response due to geologic variables could effect the success of forecasts of coastal inundation as a result of climate change. Cabo Polonio, Uruguay

21 WORKING IN THE SURF ZONE 10 R/V Pelican, Amphibious Landing Craft LARC, Amphibious Vessel

22 2 WHY STUDY COASTAL CHANGE? Department of Defense concerns Loss of coastal infrastructure Loss of recreational areas