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  2. Activity : N-OF05C Overflow Test (Damage repair + RTM)
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Activity Name:

N-OF05C Overflow Test (Damage repair + RTM)

Activity Numbre:

69

Activity type

Strength test

Involved Workpackage

Flood defences
Emergency response
Knowledge infrastructure

Objective

This test is part of a series of tests of emergency / temporary repair strategies.

Activity Brief descriptor

Linked to theme(s):

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

Activity Time

Start Date:

Nov. 17, 2021, 8 a.m.

End Date:

Nov. 18, 2021, noon

Active time length:

Days:

1

Hours:

None

Other:

4:30 hours of overflow

Location

Levee stretch:

VI

Coordinates/ Latitude (WGS):

51.34852

Coordinates/ Longitude (WGS):

4.22893

Coordinates/ Altitude (mTAW):

12.0

Descriptor:

Landward side of levee.

Other references:

Lambert '72 cooridnates: X = 140257.8 m ; Y = 226535.6 m.

Data

Data: 1

Data type: Timeseries
Description: Timeseries of Discharge, Water Height and Current Velocity in different positions on the levee slope.
Date availability: None
Find at: https://stowanl-my.sharepoint.com/:f:/g/personal/llhpp_stowa_nl/EvlsCeZhq-tGqDmDAI2wo4cBrcGJ9nYKy5P_uSodtZ1bGg?e=BEExyQ
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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
Find at: https://stowanl-my.sharepoint.com/:f:/g/personal/llhpp_stowa_nl/EjX8K2wG6XhApjxEr6h09yUBxwTYxWNDcmJ5psChD6Jmow?e=aiBXgU
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Relationships with other activities

Detaled information about the activity

Pre-conditions

Repaired section, with 'reinforced turf mat' (geogrid and hydroseeding'). Vegetation has developed but is still sparse: clay soil is visible in between plants, so no dense vegetation (root) system has developed.

Activity Descriptor

A total time of 4:30 hours of overflow in several episodes. Large-scale erosion of the soil under the grid was observed.

Equipments

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

Limits

During Activity

Large-scale erosion of the soil under the grid was observed.

Post-activity conditions

Large-scale damage to the cover layer.

Immediate Results

As long as the vegetation cover is not well developed, including a dense root system and completely covered soil, the emergency repair does not give protection against overflow.

Results /Conclusion

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

An integration report will be added later (February 2023) as knowledge document.
The integration report discusses insights gained from both the steady overflow and wave overtopping tests.
under development

Other key information