Upstream and Downstream Surface Water Elevations

Three main water elevations data were required during the testing series. The upstream water elevations, downstream water elevations and the surface water elevations at the downslope testing area of the riprap.

The water elevations data at the upstream area and downstream of the hydraulic model was important for use as boundary input data into the HEC-RAS numerical model simulations. The water elevations in the downslope riprap testing area were valuable in the physical determination of the water depth over the downslope riprap bed area. This section of the chapter summarises how the surface water elevations were determined, and the results obtained in each test.

4.2.1 Surveys

The total station was used to determine the required surface water elevations and the riprap bed elevations. Similar to real life river surveys, the difference between the bed survey elevations and the water surface elevations is generally regarded as the average water depth. In this thesis, the same definition was used, and the water depth was defined accordingly.

Therefore, to determine the water depths on the physical model, survey data with surface water elevations and the top of the riprap elevations was captured with the total station and stored on the controller.

4.2.2 Data Retrieval and Storage

All the data that was stored in the total station controller was retrieved with the Leica Geo Office 8.3 software and transferred to the computer. The elevation data was then exported from the Leica Geo Office 8.3 software to excel sheets as XYZ coordinate data. All the data points were stored in an orderly manner according to the testing series and test number. Good data management practice was critical in ensuring that the data was easily found and used when required because the coordinates and elevations data that were captured for the whole thesis were large and if not well managed it would cause inconvenience to find lost or misplaced data.

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4.2.3 Golden Surfer v15 Software

A software to plot the coordinates and elevation data was required. Autodesk Civil 3D was the first software that was assessed to plot contour data. The major problem that was found with using Civil 3D, was that the process to create the required layers of contours took significant effort and time. In addition, the process of editing the contours or obtaining a cross-section of the data from CIVIL 3D was not user-friendly.

As an alternative, Surfer v15 was used to process elevation data. Surfer v15 saved a significant amount of time in processing the raw data into grids and then converting the grids to the required contour data. The Surfer software was chosen as the main data processing tool for this study for the following main reasons:

• good visualisation of the data; • took less time to plot data;

• less effort input to obtain a contour;

• could easily plot stacked layers of data if they in the same coordinate system;

• less effort required for obtaining cross-sectional data; • easy and quick to learn; and

• quick and easy to edit the layout of maps and export.

For the reasons mentioned above, Surfer software outperformed the CIVIL 3D software. Surfer v15 was found to be a useful tool for research purposes as it allows the researcher to analyse data without having to worry about the details and time to create specific plots or maps. The Surfer v15 software made it convenient for the researcher to process and analyse the elevation data.

4.2.4 Contour Generation

The first step in the determination of the required water elevations and water depths was to create layers of contours with the following datasets, for each test:

1. Bidim elevation data 2. Riprap bed elevations

4-97 The stacked contours obtained from the Surfer v15 software can be seen in Figure 40:

Figure 40: A sample of the bidim contour layer(black-grey), riprap bed contour layer(brown) and the surface water contour layer(blue-green) generated and stacked on top of each other with the Surfer v15 software.

Different colour schemes in Figure 40 were used to allow the reader to realise the different layers of contours stacked on top of one another. At the bottom (the brown colour scheme) is the average top of the riprap layer. The green-yellow-white-blue colour scheme layer was the surface

4-98 water elevation layer at a specific Qi. The bidim layer(black-grey) was not visible from the plan view because it was underneath the riprap layer (slightly visible at the far right and left ends of the contour map in Figure 40).

Figure 41 shows a 3D representation of the stacked data (only the surface water and riprap bed elevation are shown). The 3D layers were used to

check if there were any deficiencies in the data and where they could be. For instance, in a few cases, the needle would move slowly down and capture significantly incorrect points on the surface of the water. So, the 3D model was used to check for such errors in the data.

Figure 41: A 3D representation of the elevation data of the riprap bed (brown layer) and surface water level (blue-green) that was obtained using Surfer v15.

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4.2.5 Cross-Sectional Data

The cross-sectional data was extracted from the contour data to obtain the upstream and downstream elevations of the model. To extract the cross-sectional data, a Surfer v15 mapping tool was used to retrieve the data. To use the tool, the software user was required to draw a line from downstream to upstream to indicate where the required cross-sectional data must be retrieved. The resulting cross-sectional profile looked like the one in Figure 42:

Figure 42: A typical longitudinal cross section through the three elevation data layers at Qi.

The Surfer v15 software accurately plotted the different elevation data layers in the correct order. The grey layer was the top of the bidim, the brown layer was the riprap bed elevation and the blue layer was the surface water elevation at the pertinent Qi.

The challenge that arose during the processing of the data was when the upstream water elevation, downstream water elevation and water depth needed to be determined from the created Surfer v15 longitudinal cross-sectional profile. The first option was to read off values manually from the diagram similar to Figure 42. The problem with reading off values by eye is that it would be easy to make an incorrect reading. Thus, it was decided that the cross- sectional data from Surfer v15 must be exported to Microsoft Excel. When the data was re- plotted on Excel it could be easily manipulated with the Microsoft Excel mathematical functions to determine accurate elevations at the upstream and downstream sections of the flume.

Moreover, Excel was a useful tool to use in calculating the water depth at the testing area with the exported data. Figure 43 shows a typical Microsoft Excel-created surface water profile developed from the data imported from Surfer v15.

Riprap bed elevation profile Surface water elevation profile Top of bidim profile

4-100 Figure 43: A typical surface water profile re-produced on Excel.

The legend in Figure 43 shows the three sets of the elevation data that were plotted onto the profile in Figure 43. In Figure 41 the surface water elevations began at station 2m, but in Figure 43 the upstream surface water elevation was extrapolated, with the average value of the upstream surface water elevation up to station 0 m. Similar to the downstream elevations, the average downstream surface water elevation value was extrapolated and assumed to be the relevant downstream elevation. For each test, the upstream and downstream elevations were determined by creating the surface water profiles as described in this section. A summary of the measured upstream and downstream elevations can be found in

section 4.2.6. 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 E le v at io n ( m ) Station (m)