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  2. Activity : N-OF11 Overflow Test (Reed vegetation)
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Activity Name:

N-OF11 Overflow Test (Reed vegetation)

Activity Numbre:

75

Activity type

Strength test

Involved Workpackage

Flood defences
Emergency response
Knowledge infrastructure

Objective

The N-OF11 overflow test is executed at a levee section characterized by the presence of a reed field.

Activity Brief descriptor

Overflow test to assess the resistance against overflow events of a reed field on a soft, moist soil patch on the lower slope of the levee.

Linked to theme(s):

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

Activity Time

Start Date:

Dec. 13, 2021, 1:30 p.m.

End Date:

Dec. 13, 2021, 2:30 p.m.

Active time length:

Days:

0

Hours:

1.0

Other:

Total overflow event duration: 27 minutes.

Location

Levee stretch:

VI

Coordinates/ Latitude (WGS):

51.34632681

Coordinates/ Longitude (WGS):

4.23171917

Coordinates/ Altitude (mTAW):

11.8

Descriptor:

Test section on Dutch Levee. Levee slope 21°.

Other references:

Lambert'72 coordiantes: X = 140451.4 m; Y = 226291.7 m.

Data

Data: 1

Data type: Report + Timeseries + Images
Description: The data of the overflow test is reported in the Factual Data report and the data is stored on the P2C Onedrive.
Date availability: None
Find at: https://stowanl-my.sharepoint.com/:f:/g/personal/llhpp_stowa_nl/Epl2Szxq_E1PtAbusQKK1CoB5BydqC7qLAdorR89Vx-7vg?e=GqfWOP
Media avaliable:
Find media:

Relationships with other activities

Detaled information about the activity

Pre-conditions

Upper part of the levee slope: well maintained levee slope in normal condition. Lower part of the levee slope: soft, moist soil patch overgrown with grass and reed (not mowed). See factual data report for more information.

Activity Descriptor

Plan: Perform overflow until damage.

Equipments

Equipment: 1

Equipment: 2

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)

Sensor: 1

Water height (ultrasonic)

Sensor: 2

Water velocity (EM)

Sensor: 3

Cameras
Surface images of initial and end state. Images of flow patterns.

Limits

During Activity

Fast erosion and soil destabilization. See factual data report for more information.

Post-activity conditions

Lower part of levee slope has collapsed after less than 30 minutes.

Immediate Results

- The presence of a reed and unmowed vegetation section on a soft and moist soil patch, does not withstand an overflow event. After less than 30 minutes, significant damage is present. - The root system of given reed patch does not stabilise the soil in between the roots, but give rise to fast significant erosion.

Results /Conclusion

Infrastructure Knowledge

Factual data report: https://stowanl-my.sharepoint.com/:w:/g/personal/llhpp_stowa_nl/EX5yYnuJ-EBBjoKAxAwg8LkBef8ra9V_-GHjzbkz0Was8g?e=pyaUSq Factual data report annexes: https://stowanl-my.sharepoint.com/:w:/g/personal/llhpp_stowa_nl/EWIzoxIhxopCryc6744YgHYBBWr_0fhoGpJ_1pSy0_tM2w?e=pY8Hc6 An integration report: Will be added later.

Other key information