Drainage intensity describes indirectly the moisture conditions and can thereby be used as a proxy for the water table.
Limited field data and modeling results indicate that nitrogen (N) loss in drainage water is proportional to subsurface drainage intensity (DI).
The practice of increasing drainage intensity (decreasing drain spacing) beyond recommended values appears to not significantly affect crop yield but may substantially increase drainage discharge and nitrate-nitrogen losses to surface waters.
Even though the significance of the explanatory variables were different between mire complex zones, the variables describing habitat conditions, such as drainage intensity and site fertility, contributed most to the models.
Simulation results suggest that a drainage system designed for a drainage intensity of 0.46 cm day−1 with a drain depth of 1.05 m and drain spacing of 25 m is sufficient enough to maximize crop production (average relative yield ≈98%) while minimizing subsurface drainage and its associated nitrate-nitrogen (NO3-N) loss.
Faniran (1968) defines the drainage intensity as the ratio of the stream frequency to the drainage density.
The drainage intensity (Di) is the ratio of the 'Sf' to the 'Dd' of the basin (Faniran 1968).
With the low values of drainage density, stream frequency and drainage intensity, surface runoff is not quickly removed from the watershed, making it highly susceptible to flooding, gully erosion and landslides.
Relief ratio (Rr) gives indication of overall steepness of a drainage basin and the intensity of erosional process operating on the slope of the basin (Schumn 1956).
On the other hand, in the watersheds of Shobanapuram, Sengattuppatti, Thalugai, Kallar, Periyakaruppu Odai and Kalungi, on account of their high drainage density, the rainfall intensity, rock resistivity and mean annual run off are likely to be high whereas the infiltration capacity/permeability and vegetation cover are likely to be lower, and further these watersheds are less well drained.
