Experimental dataset on water levels, sediment depths and wave front celerity values in the study of multiphase shock wave for different initial up- and down-stream conditions

This data article presents a rich original experimental video sources and wide collections of laboratory data on water levels, sediment depths and wave front celerity values arose from different multiphase dam-break scenarios. The required data of dam-break shock waves in highly silted-up reservoirs with various initial up- and down-stream hydraulic conditions is obtained directly from high-quality videos. The multi-layer shock waves were recorded by three professional cameras mounted along the laboratory channel. The extracted video images were rigorously scrutinized, and the datasets were obtained through the images via image processing method. Different sediment depths in the upstream reservoir and dry- or wet-bed downstream conditions were considered as initial conditions, compromising a total of 32 different scenarios. A total of 198 original experimental videos are made available online in the public repository “Mendeley Data” in 8 groups based on 8 different initial upstream sediment depths [1], [2], [3], [4], [5], [6], [7], [8]. 20 locations along the flume and 15 time snaps after the dam breaks were considered for data collecting. Consequently, a total of 18,000 water level and sediment depth data points were collected to prepare four datasets, which are uploaded in the public repository “Mendeley Data”. A total of 9600 water level data points could be accessed in [9], [10], while 8400 sediment depth data points are available online in [11], [12] and could be utilized for validation and practical purposes by other researchers. This data article is related to another research article entitled “Experimental study and numerical verification of silted-up dam-break” [13].

Water level data Sediment depth data Wave front celerity Image processing method Dam-break Silted-up reservoir Multiphase shock wave a b s t r a c t This data article presents a rich original experimental video sources and wide collections of laboratory data on water levels, sediment depths and wave front celerity values arose from different multiphase dam-break scenarios. The required data of dam-break shock waves in highly silted-up reservoirs with various initial up-and down-stream hydraulic conditions is obtained directly from high-quality videos. The multi-layer shock waves were recorded by three professional cameras mounted along the laboratory channel. The extracted video images were rigorously scrutinized, and the datasets were obtained through the images via image processing method. Different sediment depths in the upstream reservoir and dry-or wet-bed downstream conditions were considered as initial conditions, compromising a total of 32 different scenarios. A total of 198 original experimental videos are made available online in the public repository "Mendeley Data" in 8 groups based on 8 different initial upstream sediment depths [1][2][3][4][5][6][7][8] . 20 locations along the flume and 15 time snaps after the dam breaks were considered for data collecting. Consequently, a total of 18,0 0 0 water level and sediment depth data points were collected to prepare four datasets, which are uploaded in the public repository "Mendeley Data". A total of 9600 water level data points could be accessed in [9,10] , while 8400 sediment depth data points are available online in [11,12] and could be utilized for validation and practical purposes by other researchers. This data article is related to another research article entitled "Experimental study and numerical verification of silted-up dam-break" [13] .  Table   Subject Civil and Structural Engineering Specific subject area Hydraulic structures and dam engineering Type of data Original videos Tables  Images  Charts  How data were acquired Measured by means of image processing method using experimental high-quality video images Data format Both raw and analyzed Parameters for data collection The water levels, sediment depths datasets and wave front celerity values were rigorously measured and classified for different initial conditions including 8 upstream reservoir silting degrees (sediment depths) while the downstream bed was initially dry or wet with 3 standing water depths of 2, 4 and 5 cm which totally constituted 32 distinct dam-break scenarios. Description of data collection The water levels and sediment depths data were measured by scrutinizing high-quality video images for 20 locations along the flume and 15 time snaps after the dam breaks. A total of 18,0 0 0 data of water levels and sediment depths are presented in this data article. The values of wave front celerity were measured via image processing using extracted video images, firstly for several 1-m-long intervals through downstream channel bed. ( continued on next page )

Value of the Data
• These datasets could help to obtain a better scientific comprehension of water levels and sediment depths variation in multiphase shock waves propagation. • This data article can improve the technical understanding of wave front celerity in dam-break shock flood phenomenon particularly when its reservoir is silted-up. • The original experimental videos presented in this data article could be utilized for future studies and facilitate reproducibility of wide information in the related article as well. • The wide obtained datasets could be utilized by other researchers in future studies on siltedup dam break in wet prone areas for validation and practical purposes. • The literature is sparse on silted-up dam breaks, and no studies have reported or provide datasets concerning water levels, sediment depths and wave front celerity in the case of such phenomenon in wet downstream conditions [14,15] .

Data Description
In this data article, a large collection of experimental data in investigation of dam break flood waves under different initial upstream sediment depths with dry or wet downstream conditions is provided. The water levels and sediment depths at different locations in the laboratory channel and at various time snaps after the dam break were carefully extracted and presented as well as evaluated rigorously in related research article [13] . The dam break flood wave characteristics in different initial conditions have been well studied, specifically for water-filled reservoirs (without sediment) [16][17][18] . This topic is also investigated in the case of dam breaks with dry downstream and high sediment depth in their reservoir, which are called silted-up reservoirs [14,15] . However, the literature is sparse on silted-up dam breaks, and to the best of the authors' knowledge, datasets of water level and sediment depth for silted-up dam breaks with wet downstream conditions have not yet to be reported. A set of wave front celerity data of dambreak multiphase flood has been presented in this data article as well. The wave front celerity of dam-break is previously investigated analytically, experimentally and numerically for waterfilled reservoir with fix and movable bed condition [18][19][20][21][22] . Although, this topic is addressed Table 1 The list of different dam-break scenarios which reported in this article (modified from [13]  for silted-up reservoirs with dry-bed downstream condition [14,15] , to the best of the authors' knowledge the data collection of wave front celerity in case of silted-up dam break with wetbed downstream condition has never been reported to date!

Dam break scenarios
In this data article, the water level, sediment depth and wave front celerity data were measured for different dam break scenarios. Eight distinct reservoir sediment depths, including 0 (no sediment), 3, 7.5, 15, 17.5, 20, 22, and 24 cm, were considered as the upstream initial conditions. The initial level of the reservoir was adjusted to 30 cm in all experiments, hence, the reservoir height is occupied by different upstream sediment depths of 0% −80%. In addition, various initial downstream conditions were considered, including dry-or wet-bed downstream with 3 different standing water levels of 2, 4, and 5 cm. In general, all data collection and videos reported in this data article are related to above-mentioned initial conditions comprised 32 distinct dam-break scenarios, which are listed in Table 1 .

Water level and sediment depth data
The experimental data of water levels and sediment depths were measured and classified according to different locations along the laboratory flume and various time snaps after the dam break. 20 locations along the flume were considered as survey points, where the first location is the reservoir at the starting point of the flume (0.00 cm). The other locations are 76, 102, 127, 137, 142, 147, 152, 157, 167, 177, 187, 242, 247, 252, 257, 262, 352, 452, and 552 cm from the reservoir's beginning ( Fig. 1 ). Gaps between the points near the dam location and 1 m after that were less than other areas along the flume, to ensure enough measurements are performed in this area of high turbulence and rapid depth change and the specific area studied downstream of the dam. The dam section (gate) is located at 152 cm and includes the dam section. 15 screen shots based on the elapsed time after the dam broke were taken at 0.04, 0.08, 0.12, 0.2, 0.3, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0, and 6.0 s from video images for data extraction. Intervals between the snaps were shorter immediately after the dam break and increased gradually.
In general, a total of 18,0 0 0 water level and sediment depth data points were obtained then prepared into four datasets, which have been uploaded in the public repository "Mendeley Data" [9][10][11][12] . This data collection includes 9600 water level data and 8400 sediment depth data points, which have been made available as four distinct datasets: (i) Experimental dataset on water levels ( n = 3600) in studying the influences of dry-and wetbed downstream conditions on multiphase dam break flood wave, while 0 to 25% of the dam reservoir is occupied by sedimentation [9] . (ii) Experimental dataset on water levels ( n = 60 0 0) in the investigation of silted-up dam break flood wave for dry-and wet-bed downstream conditions, while 50 to 80% of the dam reservoir is filled up with sediment [10] . (iii) Experimental dataset on sediment depths ( n = 2400) in analyzing the influences of dry-and wet-bed downstream conditions on multiphase dam break flood wave, while 0 to 25% of the dam reservoir is occupied by sedimentation [11] . (iv) Experimental dataset on sediment depths ( n = 60 0 0) in the study of silted-up dam break flood wave for dry-and wet-bed downstream conditions, while 50 to 80% of the dam reservoir is filled up with sediment [12] .
Herein, to facilitate the reader's technical understanding and scientific comprehension, three different data tables which presented in [9][10][11][12] are described in detail as an example of the large datasets (60 tables) that were uploaded in the public repository "Mendeley Data" [9][10][11][12] . Table 4 in [9] provides the free surface water level data at 20 different locations along the flume and 15 snap times after the dam break. The initial conditions included the upstream reservoir filled with clear water (no sediment) and a standing water depth of 5 cm in the wet-bed downstream (see Table 4 in [9] ). The free surface water level data at all the above-mentioned sections  Table 3 The dam break wave front celerity data for wet initial downstream conditions with 2 cm standing water level.
Intervals along the flume (m)  and snap times are presented in Table 6 in [10] , while the initial upstream sediment depth was 17.5 cm (58% of the reservoir height), and the downstream was initially wet with a standing water depth of 2 cm (see Table 6 in [10] ). Finally, Table 19 in [12] shows the sediment depth data, when the initial upstream sediment depth was 24 cm (80% of the reservoir height), and the initial standing water depth was 4 cm in downstream (see Table 19 in [12] ). Pertinent variables of mention include D W L and S d , which are the initial downstream water level and initial upstream sediment depth measured in centimeters, respectively. Time refers to the snap times after the sudden removal of the gate in seconds. It should be noted that the vertical column to the left of the tables indicates the distances of different locations (cm) from the beginning point of the laboratory flume. Column L indicates all 20 distinct locations along the flume and their distances from the reservoir's beginning in centimeters.

Front wave celerity data
The wave front celerity is firstly calculated in four intervals along the dam downstream which the length of each of them is 1 m. Fig. 2 shows a schematic plan view of the laboratory flume.  As it can be seen, these intervals cover 4 m length of the flume in total, from 1.  Table 2 , presents the wave front celerity values of the silted-up dam break flood in all considered intervals for different initial upstream sediment depths while downstream is initially dry. Table 3 , provides the wave front celerity values of dam break flood in four above-mentioned intervals along dam downstream for different initial upstream sediment depths while downstream is initially wet with 2 cm standing water. The wave front celerity values of dam break flood in specified intervals, for different initial upstream sediment depths while downstream bed is initially wet with 4 cm standing water are detailed in Table 4 .
Finally, Table 5 , details the wave front celerity data of dam break flood in all downstream intervals for different initial upstream sediment depths while downstream bed is initially wet with 5 cm standing water.

Original experimental videos
Herein, a rich collection of original videos are made available online in the public repository "Mendeley Data" might be utilized for validation purposes in future studies. The presented video files are related to dam break multiphase flood shock wave experiments which performed in the Shiraz University, Civil and Environmental Engineering Department's Hydraulic Lab (Shiraz, Iran). Considering three cameras which covered length of the flume, 4 different dam break scenarios and 2 or 3 repetitions conducted for each test, a total of 198 videos collected and presented in this document. The experimental videos are classified in 8 groups based on 8 different initial upstream sediment depths [1][2][3][4][5][6][7][8] . The additional explanations related to video files can be seen in explanation tables of videos ( Tables 6 -13 ).
For data extraction, a non-intrusive technique was applied to each of the video images using Grapher® software. In this method, after specifying the coordinates of two certified points on a diagonal line within each of the images, coordinates of any arbitrary point in the x and y axes can be easily obtained by clicking on that point ( Figs. 5 and 6 ). Hence, the free surface water level and sediment depth profiles for any arbitrary time after the dam break could be collected directly from the video images at any location along the laboratory channel, without disturbing the flow with any physical instrument. This method can yield high-quality and accurate data despite being laborious and time-consuming. All video images collectively comprised a total of 18,0 0 0 data points, which are available in "Mendeley Data" [9][10][11][12] . Fig. 5 (a-c) display the software interior area in extracting water level and sediment depth data. Fig. 5 (a) contains a snapshot of the shock flood wave at 0.2 s after the dam break when the upstream reservoir was filled with clear water (no sediment), and the downstream bed was dry. Fig 5 (b) presents a snapshot at 1 s after the dam break when the initial upstream sediment depth was 3 cm, and the downstream channel bed was initially wet with 2 cm of standing water. Fig. 5 (c) contains a snapshot of the multiphase flood wave at 1 s after the dam break, while the initial upstream sediment depth was 7.5 cm and the initial downstream water level was 4 cm. Fig. 6 (a-c) shows the software interior area in extracting water level and sediment depth data. Fig. 6 (a) displays a snapshot of the shock flood wave at 1 s after the dam break when the initial upstream sediment depth was 17.5 cm and the downstream bed was dry. Fig. 6 (b) presents a snapshot at 1 s after the dam break with an initial upstream sediment depth of 17.5 cm and wet downstream channel bed with 5 cm standing water. Fig. 6 (c) contains a snapshot of the multiphase flood wave at 1 s after the dam break when the initial upstream sediment depth was 20 cm with dry-bed downstream conditions. The values of wave front celerity were calculated using extracted video images firstly at four intervals along the dam downstream ( Fig. 2 ). Then, the mean values of wave front celerity through dam downstream are carefully measured and classified for all dam break scenarios. To calculate the wave front celerity Eq. (1) was used.
where, C f represents wave front celerity in ( m/s ), L i is the distances from reservoir beginning in ( m ) and t i is the time snap after the dam breaks in ( sec ). Fig. 7 , shows video images related to fifteenth dam break scenario ( Table 1 ) in which the initial upstream sediment depth was 15 cm and dam downstream bed was initially wet using 4 cm of standing water. As it can be seen, seven-time snaps of 0.1, 0.2, 0.3, 0.4, 0.6, 0.8 and 1 s after the failure of the dam are presented in the figure and the first interval is specified between two vertical red lines. Considering L 1 , L 2 , t 1 and t 2 the wave front celerity is 1.6367 (m/s), as presented in Table 4 . This process is conducted for all 32 scenarios and 4 intervals and classified in Tables 2 to  5 and then the mean values of wave front celerity through downstream channel are carefully measured for all experiment scenarios (see Table 3 in [13] ).

Statement of Consent and Authorization
The authors state that they have received informed consent from the individuals in question to publish all videos.
The individuals were freely and voluntarily consent to take part in the research study and they authorized the use and disclosure of their information in connection with the study. Those individuals have gave their explicit written consent and received a signed copy of the consent and authorization form.
Each individual who was appeared in any video has made aware in advance of the fact that such videos are being taken and of all the purposes for which they might be used, including publication in Data in Brief. Written consents will be retained by the author and copies of the consents will be provided to the Data in Brief Editors upon request.