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Activity Name:

N-OF02 Overflow Test (Clay Erosion)

Activity Numbre:


Activity type

Strength test

Involved Workpackage

Flood defences
Emergency response
Knowledge infrastructure


Measure clay erosion speeds during overflow.

Activity Brief descriptor

The initial part of the test is performed as a reference test. The clay erosion experiment on the last day of testing is aimed at measuring clay erosion rates.

Linked to theme(s):

Animal- & vegetation-induced anomalies
Erosion processes
Temporary levee repairs
Levee survey & monitoring technique
Prolonged collaboration

Activity Time

Start Date:

Dec. 1, 2021, 8 a.m.

End Date:

Dec. 3, 2021, 5 p.m.

Active time length:







Levee stretch:


Coordinates/ Latitude (WGS):


Coordinates/ Longitude (WGS):


Coordinates/ Altitude (mTAW):



Landward slope of levee.

Other references:

Lambert'72 coordinates: X=140306.5 m Y=226474.1 m


Data: 1

Data type: Timeseries
Description: Description: Timeseries of Discharge, Water Height and Current Velocity in different positions on the levee slope.
Date availability: None
Media avaliable:
Find media:

Data: 2

Data type: Photo imagery
Description: 2 portals with in total 4 cameras are used to take surface photographs of the levee slope at different times during and in between overflow activity. The surface images in between overflow blocks show damage and vegetation evolution.
Date availability: None
Media avaliable:
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Detaled information about the activity


First part of the test: levee slope in good condition. For the clay experiment, a full width step shape was excavated on the lower part of the levee.

Activity Descriptor

12 blocks of of overflow activity for a duration of 10.5 hours. Specific discharge up to 550 l/s.m.


Equipment: 1

Overflow generator.
The setup is described in Vercruysse et al. (2022): "Design and application of an overflow generator." (Ref WL2022R20_047_1)

Monitoring & Sensors

- Overhead cameras (4) - Acoustic water height sensors - Electromagnetic current velocity sensors - Discharge sensor (EM or acoustic)
Description of the hydraulic conditions of the overflow. The setup is described in Vercruysse et al. (2022): "Design and application of an overflow generator." (Ref WL2022R20_047_1)

this activity does not have sensors


During Activity

The first part of the test showed an evolution as expected based on N-OF01. No critical damage occurred. During the clay erosion experiment, clay effectively eroded and measurements were performed.

Post-activity conditions

Slope damaged due to man-made step shape excavation on the lower slope.

Immediate Results

Results /Conclusion

The evolution of the vegetated levee under normal overflow conditions corresponds to the observations for the reference section N-OF01, albeit for a shorter time span: 8 hours after 2 days of testing lead to no significant damage to the levee.For insights and conclusions concerning the erosion tests(where they are put in relation to other large and small scale tests), reference is made tovan Damme et al. (2022). Factual data report: https://stowanl-my.sharepoint.com/:w:/g/personal/llhpp_stowa_nl/EX5yYnuJ-EBBjoKAxAwg8LkBef8ra9V_-GHjzbkz0Was8g?e=pyaUSq Annexes: https://stowanl-my.sharepoint.com/:w:/g/personal/llhpp_stowa_nl/EWIzoxIhxopCryc6744YgHYBBWr_0fhoGpJ_1pSy0_tM2w?e=pY8Hc6

Infrastructure Knowledge

Two reports will be added in Februari 2023.
The clay erosion report discusses the clay erosion process and models, and experiments performed at different scales, and relations. The integration report discusses insights gained from both the steady overflow and wave overtopping tests.
under development

Other key information