The inputs required for the design of an MEL culvert include the ground levels of the stream bed or floodplain upstream and downstream of the area where the structure is to be sited. Water levels and energy levels are also required. The most appropriate way to obtain these is from a backwater analysis (HEC-Ras) of the section of the stream before construction of the bridge/culvert. A design flowrate is required as well as estimated roughness values of the constructed surfaces. A trial value for the barrel width is needed and this can be changed (reduced) to minimise the size and cost of the designed structure.

Complete performance analysis also requires further inputs such flood hydrographs and sediment characteristics of the region. To enable the program to compute the complete water surface profile through the structure, a downstream water level boundary condition is required. The simplest way to do this is to input the slope, width and Mannings n of the stream below the structure, so that a uniform flow assumption can be used to estimate a downstream depth.

Output from the program is of two types – tabular and graphical.

Tabulated data includes full set-out dimensions (offsets and invert levels) for the spiral fans and barrel of the designed structure. The radius of curvature of the iso-level lines in the fan are also listed. These data are plotted in simple graphs to enable the user to gain a visual appreciation of the shape and dimensions of the structure.

MELS performs the design and hydraulic analysis of MEL culverts.

Other important aspects of the design include surface treatment of the fans to avoid erosion, low flow channels/pipes in regions where standing water in the depressed invert of an MEL structure is undesirable and provision of adequate freeboard. These issues are discussed in the Design Guidelines but are not part of the MELS software.