Calculate the ‘equal area slope’ for the creek profile (longitudinal section ) shown below. Information:

Extracted from the figure is shown in the table. Please explain step by step how this area under polygons is calculated. All units are in square meters in area. Length and elevation in meters.
 

  

Length Elevation Elevation from outlet Area under each polygon 0 12 1400 15 2100 2500 20 25 30 2800 3050 35 3150 40 x www xwo: 13 18 28 Area under the curve = Total 22475= H x L/2 2100 3850 4200 4650 5125 2550 22475 area under the equal area slope = 22475 x 2/3150 = 14.27 = Se (m/m) 14.27/3150-0.00453 Se(%) = 0.45% Elevation from contours (m) 45 40 35 30 25 20 10 5 0 0 500 1000 Se L 2000 1500 Length from the outlet (m) 2500 3000 H 3500