Adding flowline length, perimeter, area, bed_area, and volume to all transects

[arashmodrad]

We should include the following in our next iteration of transect generation

• Include a column identifying ML vs DEM points
• Ensure there are transects at immediate beginning and end of each flowline for mass preservation
• Include flowline length (FL) from current transect to upstream transect
• Include ML perimeter (P) for all transects
• Include ML cross-section area (A) for all transects
• Include ML bed_area for all transects bed_area = FL * P
• Include ML Volume for all transects Volume = FL * A

Note that we need to interpolate a value on left or right bank of the ML points to match the elevation of the other bank before estimating the above.

Elevation on sides are different

Elevation on both sides are equal by interpolation