MID-TERM CONFERENCE CRESTcrestproject.be/sites/crestproject.be/files/public...• Kinematic Lidar • Hydrographic • Single beam echosounder • Multi beam echosounder 23/11/2017.

MID-TERM CONFERENCE CREST

23 November 2017

Innovation in Coastal Monitoring

Alain De Wulf (Ugent, Geography Dept.)

Innovation in coastal monitoring

Outline

23/11/2017

• Why ?

• How ?

• What (tools do we use to assess) ?

• Conclusion


Outline

23/11/2017

• Why ?

• How ?


• Conclusion

Why monitor the coast ?

23/11/2017

Sand particles move !

• Dry transport (wind)

• Wet transport (tides, currents, waves)

Why monitor the sand particles

on the coast ?

23/11/2017

• Coastal Safety (flooding)

• Tourism (spatious sand beaches)

• Habitat preservation

Therefore the erosion/accretion balance must

be monitored and understood.

Classical assumption:

• Erosion during storm events

• Accretion in standard weather situations

23/11/2017

If erosion/accretion volumes are not in balance => beach

nourishment = reclamation of the beach areas (quite expensive)

Why monitor the sand particles on the coast


Outline

23/11/2017

• Why ?

• How ?


• Conclusion

How ? 1. By measuring the geometric changes

Comparison of different techniques

• Aerial

• Lidar

• Drone survey

• Terrestrial

• Static GNSS

• Kinematic GNSS

• Static Lidar

• Kinematic Lidar

• Hydrographic

• Single beam echosounder

• Multi beam echosounder

23/11/2017

23/11/2017

How: 2. By measuring the sand transport “in the dry” (Aeolian campaigns)

• By measuring the

spatial and temporal

variability of

sediment transport

on the beach with

acoustic sensors and

sand traps and sand

catchers

• By measuring

surficial moisture

content changes

• By measuring the wind conditions: wind speed and wind

direction at different heights above the surface with

meteorological stations

How ? 2. By measuring the sand transport “in the dry” (Aeolian campaigns)

How ? 2. By measuring the sand transport “in the dry” (Aeolian campaigns)

How ? 3. By measuring the sand

transport “in the wet”

• Near shore wave and

current conditions

(e.g. with ADCP,…)

• Sediment

concentration,…

23/11/2017


Outline

23/11/2017

• Why ?

• How ?

• What?

• Conclusion


Outline

23/11/2017

• Why ?

• How ?

• What is the innovation in monitoring techniques ?

• Conclusion


What is the innovation in geometric

monitoring techniques ?

23/11/2017

• Speed of acquisition- Terrestrial Lidar: 0.25 till 1 million points/s (<> 20 p/s).

• Quantity of acquisition (point density)- 1 cross-section per 5 cm (<> 50 m). - interval distance in the cross-section: 1-5 cm (<> 5m).

• Quality of acquisition- Accuracy on sub cm level in x,y,z (<> 1 dm).


What is the innovation in geometric

monitoring techniques ?

23/11/2017

Speed, density, quality =>

• Detailed 3D model instead of small set 2D profiles

• 4D (1 model per hour) with static long-range terrestrial laser scanner

=> Small (sub cm) changes and very short time ( 1 hour) changes can now be monitored.


What is the innovation in monitoring

techniques ?

23/11/2017

• Dry aeolian transport: detection of sand particle movement with automated electronic devices.

• Wet transport: • automated density and current sensors.• multi beam in intertidal zone (even in extremely

shallow water < 1 m).


Outline

23/11/2017

• Why ?

• How ?

• What tools do we use to evaluate the topographic / morphologic changes ?

• Conclusion

Software development of high precision analysis tool

• High precision digital terrain modelling tool (PC: maximum up to 8 billion grid cells with 32 Gb RAM).

• Allows:

• Sub-cm grid intervals (e.g. 300 m by 160 m grid of 1 cm cells => ca. 0.5 billion cells)

• Visualisation

• Filtering (outlier removal)

• Correlation computation

CREST meeting – January 20, 2016

How: tools to evaluate the topographic / morphologic changes

Depth Analysis



Slope Analysis

SeArch meeting – January 14, 2016

• Maximal Slope (%)


Slope Analysis


• Maximal Slope (%)• Direction of maximal slope


Slope Analysis


• Maximal Slope (%)• Direction of maximal slope• Slope in specified direction



• Maximal Slope (%)• Direction of maximal slope• Slope in specified direction• Slope curvature (second derivative model)

Slope Analysis



• Intensity values of the backscatter

Intensity Analysis



• Maximum slope of intensity values

Intensity Analysis



• Maximum slope of intensity values• Direction of maximum intensity slope

Intensity Analysis



• Intensity of the backscatter signal• Direction of maximum intensity slope• Slope in specified direction

Backscatter intensity Analysis



• Intensity of the backscatter signal• Direction of maximum intensity slope• Slope in specified direction• Slope curvature (second derivative model)

Backscatter intensity Analysis



• Without noise elimination and intensity correction => almost no correlation

• Geometric model can be improved by optimal noise filtering

• Backscatter model can be improved by corrections for distance, angle (and humidity ?)

• In the near future significant higher correlation can be expected between the improved geometry and the improved backscatter model

Correlation analysis height <> backscatter



• Local Relief (absolute difference value)• Standard Deviation (n*SD)• Boxplot (1.5 * (Q3-Q1))

Noise removal: outlier elimination

Can be applied to:

Geometric model• Depths• Slopes• Curvature

Backscatter model• Intensity• Slopes• Curvature



• Local Relief (absolute difference value)• Standard Deviation (n*SD)• Boxplot (1.5 * (Q3-Q1))

Noise removal: outlier elimination



Outline

23/11/2017

• Why ?

• How ?


• Conclusion


Conclusion

23/11/2017

• Safety, tourism and habitat protection requires accurate and frequent beach monitoring.

• Nowadays significantly more fast and accurate technologies are available as well for geometry modelling of the beaches as for dry (aeolian) and wet transport of sand particles.

• A combination of these techniques combined with simultaneous measurements allows a new and deeper insight in the mechanisms of sand transport and will connect the “small scale” observations with the “big scale” observations.

In samenwerking met

23/11/2017

Met dank aan

Monitoring wind-blown sandGlenn Strypsteen

Mid-term Conference CREST, 23/11/2017Conference Room Planet Ocean

Study area

Measurement positions

A variety of instruments are used

Sand traps capture the wind-blown sand at different heights

Saltiphones record grain impacts every second

A horizontal sand trap captures sand in downwind direction

Laser scanner measures the topography from a fixed position (TU Delft)

Or on a mobile all-terrain vehicle (Ughent)

Meteorological stations measure the wind conditions and

temperature

A typical campaign

A typical campaign

Thank you!

Glenn StrypsteenKU Leuven

Campus BrugesFaculty of Engineering

[email protected]

MID-TERM CONFERENCE CREST

23 November 2017

Beach topography: measuring techniques

14/05/2018

• 2D

• Profiles

• RTK-GNSS

Topography: traditional survey

14/05/2018

• 2D

• Profiles

• RTK-GNSS

Topography: traditional survey

3D survey

• Platform: mobile

4x4 with

• Laserscanner

• RTK-GNSS

• Motion sensor

14/05/2018

• MTLS (Lidar): Own system:

3D survey

3D survey

• Acquisition similar

to multibeam set-

up

• Boresight offsets

• Calibration

14/05/2018

3D survey

• Acquisition on site

• Survey lines

• Approx. 2-3 hours

14/05/2018

3D survey

• Challenges

14/05/2018

3D survey

14/05/2018

Result: after cleaning

Comparing techniques

• Drone survey

• Long distance

laser

• Lidar

14/05/2018


• Drone survey

• Long distance

laser

• Lidar

14/05/2018


• Drone survey

• Long distance

laser

• Lidar

14/05/2018

In samenwerking met

14/05/2018

Met dank aan

MID-TERM CONFERENCE CRESTcrestproject.be/sites/crestproject.be/files/public...• Kinematic Lidar • Hydrographic • Single beam echosounder • Multi beam echosounder 23/11/2017.

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