Everything about B-OF04 Overflow Test (Tree + small cliff annomaly)
id;activity_name;activity_type;activity_descriptor;breaching;animal;erosion;temporary;levee_survey;prolonged;start_date;end_date;date_length_day;date_length_hour;date_other;levee_stretch;location_x;location_y;location_z;location_descriptor;location_other;objectif_important;objectif_knowledge;pre_condition;act_des;monitoring_process;monitoring_reasoning;limits;during_activity;post_activity;activity_result;results_conc;knowledge_desc;ref_links;wrk_1;wrk_2;wrk_3;key_info
79;B-OF04 Overflow Test (Tree + small cliff annomaly);Other;;False;True;True;False;False;False;2020-11-16 08:00:00;2020-11-16 17:00:00;;1.0;;IV;51.34195;4.23774;11.2;Landward side of levee.;"Lambert '72 coordinates:
X=140870.10 m; Y=225804.40m.";The test is aimed at observing the influence of the presence of a tree on the levee toe.;How does a tree on the levee toe affect the stability and erosion strenght of the levee?;A section with a tree situated a few meters outside the levee toe was chosen to be tested to study the influence of the tree presence (under the expectation that some form of scour would occur). Also, a small (minor) cliff (see also the B-OF5 test for a large cliff structure) was present however, it was estimated that it would not affect the experiment significantly. The cliff was also related to the animal activity around the tree area (it is thought that it is the sleeping place of sheep).;1h27 of overflow at a discharge of 160 l/s.m in several blocks to observe damage evloution.;- 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)";;"Shortly after the start of the experiment, it was observed that ‘sand boils’ were present outside the test strip. On the left side of the test section (i.e. southwards), water and sand was emerging from small (mice?) holes near the levee toe area. At 11:58, the test resumed for the last time, until 12:05. The total pumping time was only 67 
minutes before final damage. The field hypothesis was that sand eroded from under the cover layer (i.e. sand from the levee core is transported, even partially outside the test section) created a mass deficit and destabilized the cover layer (undermining), leading to failure (sudden collapse)";Failure of the lower levee slope.;"- The presence of a tree and surface root system enhances erosion of the soil around the tree. However progress was slow without quickly escalating to any (critical) damage.
- The small cliff on the lower part of the slope a couple meters in front of the tree, created by sheep did not give rise to direct damage. 
- The presence of burrows (mice, mole) is believed to have provoked the flow of water under the clay cover, through the inner sand core. This fairly quickly led to outflow of sediment  near the toe of the levee (notable adjacent to the test section). The resulting mass deficit  lead to ground subsidence and finally a collapse of the top layer into the created void.
- Dewatering of the upwind sediments was observed during which collapse of the sand and tearing of the overlying clay cover occurred, effectively resulting in upward moving headcut erosion.";Factual data report + Annexes: https://stowanl-my.sharepoint.com/:f:/g/personal/llhpp_stowa_nl/EvdAZOO-zylAqEWS8-SEiC4BQ5xCAuFXklsysJXnkcVYaQ?e=XDeXq8;An integration report will be added later (February 2023) as knowledge document.;under development;True;False;False;


All DATA concerning B-OF04 Overflow Test (Tree + small cliff annomaly)
data_type;data_descripion;date_date;data_find;data_media;data_media_find
Hydraulic timeseries;Water height, discharge, velocity measurements.;;https://stowanl-my.sharepoint.com/:f:/g/personal/llhpp_stowa_nl/EsLyC1x3KBlKuZdIJ3YsMXsBt3fc0optOX9DRYXGSl2CYg?e=Ch7SHH;;
Surface state photographs;;;https://stowanl-my.sharepoint.com/:f:/g/personal/llhpp_stowa_nl/Ejfq3KC-En1BvJW6AoAdrMQBb7VdGslKTzsUdP3VaymBRA?e=I6Ztc1;;


All EQUIPMENTS concerning B-OF04 Overflow Test (Tree + small cliff annomaly)
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All SENSORS concerning B-OF04 Overflow Test (Tree + small cliff annomaly)
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