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Activity Name:

Wave overtopping experiment bare clay section 2-1

Activity Numbre:

103

Activity type

Strength test

Involved Workpackage

Flood defences
Emergency response
Knowledge infrastructure

Objective

these tests are aimed at measuring the erosion rate of the clay layer underneath a grass sod on the landside slope of a levee, in order to enable the determination of the residual strength of the levee after failure of the grass. The results can be used to test and validate erosion models – both current models and future models.

Activity Brief descriptor

Right before the start of a test on a section, the upper 20 cm (including the grass sod) will be removed over a distance of 3.5 m long and 4m wide. This section was located in between 15 and 18.5m downstream of the outflow opening of the overtopping simulator and subjected to regular waves to be used in the calibration of an erosion relation

Linked to theme(s):

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

Activity Time

Start Date:

Feb. 3, 2022, 2:57 p.m.

End Date:

Feb. 3, 2022, 2:57 p.m.

Active time length:

Days:

1

Hours:

4.0

Other:

Location

Levee stretch:

Other

Coordinates/ Latitude (WGS):

139735.0

Coordinates/ Longitude (WGS):

226778.0

Coordinates/ Altitude (mTAW):

None

Descriptor:

15-18.5 m downstream of the outflow opening of the wave overtopping simulator located on the dike crest. The clay was removed on the landside slope. The bottom end of the test section is approximately 1m from the landside toe.

Other references:

Data

Data: 1

Data type:
Description:
Date availability: None
Media avaliable:
Find media:

Relationships with other activities

Detaled information about the activity

Pre-conditions

The grass was removed over a section of 3.5m x 4m wide, and a depth of 20 cm using a crane.

Activity Descriptor

The second stretch will be tested with a realistic irregular wave pattern. Based on discussions in the Erosion Theme group of Polder2C’s and several recent memos by Jentsje van der Meer, there are two basic possibilities. A: in case of some damage, or a lot of damage, on the first stretch loaded with the regular waves, apply river conditions, increasing the severity: - lower section: Hm0 = 0.5 m, water level at the crest, Tp = 2.53 (s), average overflow discharge of qov = 60 l/s. - middle section: Hm0 = 1.0 m, water level at the crest, Tp = 3.58 (s), average overflow discharge of qov = 10 l/s. - upper section: Hm0 = 1.0 m, water level at the crest, Tp = 3.58 (s), average overflow discharge of qov = 50 l/s. B: in case of hardly any damage on the first stretch, then start with the more severe river conditions and end with moderate sea conditions: - lower section: Hm0 = 1.0 m, water level at the crest, Tp = 3.58 (s), average overflow discharge of qov = 10 l/s. - middle section: Hm0 = 1.0 m, water level at the crest, Tp = 3.58 (s), average overflow discharge of qov = 50 l/s. - upper section: Hm0 = 2.0 m, water level at the crest, Tp = 5.66 (s), average overflow discharge of qov = 30 l/s. In all cases, the basic duration of each test is 2 hours. For these tests, the requirement of waiting for 60 seconds every 10 waves to get a drier slope is dropped, as it is envisaged that the slope will get sufficiently dry at least every time the wave overtopping simulator is filled for a large wave.

Equipments

this activity does not have equipments

Monitoring & Sensors

10 GoPro's for photogrammetry for monitoring the difference in erosion depth between waves and for determining the front velocities of waves
To be able to derive an erosion relation

this activity does not have sensors

Limits

During Activity

Post-activity conditions

Immediate Results

Results /Conclusion

Infrastructure Knowledge

Erosion relation for wave overtopping on clay
This activity was used to calibrate this relation

Other key information