1. Spatio-temporal Analysis of Beach Morphology using LIDAR, RTK-GPS and Open Source GRASS GIS
Helena Mitasova Department of Marine, Earth and Atmospheric Sciences, NCSU, Raleigh, T. Drake, MEAS NCSU, R. Harmon, US Army Research Office, D. Bernstein CMWS, Coastal Carolina Univ. SC, H. C. Miller, USACE FRF Duck

2. Goal short-term coastal topography evolution by
- explore the possibilities to gain new insights into
short-term coastal topography evolution by
combining modern mapping technologies with
Open source GRASS GIS
- provide methodology for cost effective short-term
monitoring and analysis of topographic change to
support sustainable coastal management
- quantify the spatial and temporal changes in beach
morphology before and after human intervention
at Bald Head Island, NC

3. Mapping technologies Challenges :
Bathymetry:
multibeam and conventional sonar
(J.McNinch, H.Miller)
Beach topography:
Real Time Kinematic GPS (D. Bernstein)
Coastal topography:
LIDAR
USGS/NOAA ATM-II
Challenges :
massive data sets, oversampling, noise
complex surfaces with important subtle features
anisotropy and heterogeneous coverage

4. Integrating digital coastal data and GIS
Open source GIS: GRASS5
grass.itc.it
General purpose GIS for raster, vector, site and
image data processing, analysis and visualization
Developed at US Army CERL , GPL in 1999
GRASS GIS
RST interpolation
topoanalysis
map algebra:
change analysis
DEM time series
slope, curvatures
shoreline change
1st ,2nd order diffs
volume change
visualization
RTK GPS
LIDAR
points

5. Spatial Approximation using RST
Gridding with high accuracy and detailed representation of morphology can be obtained by RST (Regularized Spline with Smoothing and Tension) :
LIDAR data: 1m binning
flexibility: tension and smoothing,
simultaneous computation of slope, aspect, curvatures,
segmented processing for large data sets
formally equivalent to universal kriging (covariance function determined by smoothness seminorm)
physical basis: minimum energy surface
3m binning
1m approximation by RST
H. Mitasova

6. Bald Head Island Human impact on evolution of shore
topography and nearshore bathymetry:
channel deepening and re-alignment,
beach nourishment in 2001.
Cape Fear Rv
elevation
[m]
LIDAR
RTK GPS
re-aligned channel
Single and multi beam sonar 2000, 2001, 2002
Integrated 10m resolution model from multiple sources

7. 2D shoreline change A A B 1998: LIDAR 0m
Dec. 02: 21m beyond pre-nourishment A A
1997
2000
2001
2002 B A
LIDAR – m 10m/y
RTKGPS – m 42m/y B
LIDAR – m 12m/y
RTKGPS – m 17m/y
1998: LIDAR 0m
2000: LIDAR 0m
2001 Dec.: RTK GPS
after nourishment

8. South Beach evolution 1997-2000
Overlayed 1997 and 2000 LIDAR surfaces: central section is relatively stable, rest
erodes while changing its shape and moving landwards
Annual sand loss rate:
3500 m3/ha
Shoreline
erosion rate
10m/year
15% of sand
was deposited
behind the foredune:
landward
movement
West
Center
East
convex -> concave
2000
z>0m
z<0m
stable
pivot area
stable
concave -> convex

9. Slope and curvature High erosion area 1998 Slope 2000 Curvature
Interpolated by RST at 2m resolution with high tension parameter
Slope
2000
concave
convex
Curvature
H. Mitasova

10. Slope and curvature change
Severely eroding area approximated and analyzed by RST
1998
Slope
Profile curvature
concave
convex
2000

11. South Beach change: 1997-2000 Elevation change 1997-2000
Volume change:
loss: 376,000 m3
gain: 30,000 m3 m
loss
gain
acceleration
Second order elevation change
H. Mitasova

12. RTK GPS 2001-2001 isotropic RST anisotropic RST ~250m
cros-shore profiles
+ shoreline survey pattern
~250m
cross-shore + long-shore profiles
survey pattern
RST with anisotropic tension
H. Mitasova

13. RTK GPS surveying pattern
Binned LIDAR data were sampled by RTK-GPS survey points.
DEM was then interpolated and compared with the LIDAR data:
4643 grid points for 5m, grid points for 3m resolution.
survey pattern / RST gridding no. of points MAE [m] RMSE
csh profiles / isotropic /
csh profiles / anis. optim /
lsh profiles / anis., optim /
csh+lsh profiles / anis., optim /
same at 3m resolution /
csh+lsh profiles / anis., opt subset
DEM approximated from cross-shore profiles is the least accurate.
Long-shore profiles, anisotropy and optimized approximation
parameters can significantly improve the accuracy of DEM.
H. Mitasova

14. Pre-nourishment 2000 LIDAR
H. Mitasova

15. Change after nourishment
LIDAR RTK GPS Dec. 2001
1 million m3 of sand added
H. Mitasova

16. Change after nourishment
LIDAR RTK GPS May 2002
H. Mitasova

17. Change after nourishment
LIDAR RTK GPS Sep. 2002

18. Change after nourishment
LIDAR RTK GPS Dec. 2002

19. Change after nourishment: profiles
LIDAR 2000
RTKS: Dec. 2001
May 2002
September 2002

20. Elevation change after nourishment
Sep Dec. 2001
RTK GPS
Aug Fall 1997
LIDAR
Sep Aug. 2000
RTK GPS - LIDAR
H. Mitasova

21. Volume and shoreline change
time period loss gain loss rate [m3] [m3] [m3/ha.year]
1 y
2 y
3 y
5 mo Dec.01 - May
4 mo May 02 - Sep
4 mo Sep 02 - Dec
H. Mitasova

22. Zalewski: June 2001 Bernstein December 2002

23. Conclusions I
Combination of modern mapping techniques with Open source GIS provides unique insight into 3D coastal topography evolution at high spatial and temporal resolution.
GIS based analysis and visualization allows us to quantify the observed changes (elevation, shoreline, volume, slope and shape) and evaluate effectiveness of stabilization measures.
The developed methodology is being further enhanced and applied to other areas.
H. Mitasova

24. Conclusions II Bald Head Island
Analysis based on LIDAR and RTK GPS data showed systematic, spatially variable erosion of the beach accompanied with beach shape change. After renourishment the rates increased in the west section and the beach became more stable in the east.
Future
Analysis of the entire area as a single system:
- bathymetry (fate of eroded sand: back to channel, CF shoal, sandbars ?)
- new LIDAR survey
- modeling (SBEACH, DELFT3D)
H. Mitasova

25. Acknowledgment: Cape Fear change 1997 - 2002
This project is funded by the NRC/ARO fellowship.
In addition to observations acquired by co-authors, data from NOAA-USGS (LDART), USACE FRF Duck NC (FRF web site) and UNC Wilmigton (Anders et al. 1990, Clearly et al. 1989) were used.
12/ / /
Cape Fear change
H. Mitasova

26. Cape Fear elevation change
LIDAR (grey) RTK GPS Dec Dec. 2002
Dec Dec Dec. 2002

27. Change after nourishment
LIDAR 2000
September 2002
December 2002

28. Bald Head Island shore change
Historical change ~
Recent change
after Cleary et al. 1989
1998: LIDAR 0m
2000: LIDAR 0m
2001 Dec.: RTK GPS
after nourishment
800m
Shoreline rotates
around pivot area