Watershed Morphometry

The diameter of a circle having the same area as a watershed of $A = 78.54\text{ km}^2$ is $D = \sqrt{\frac{4 A}{\pi}} = \sqrt{\frac{4 \times 78.54}{3.1416}} = \sqrt{100} = 10\text{ km}$. If the maximum basin length is $L = 12.5\text{ km}$, the Schumm elongation ratio $R_e = D / L$ is: