The total length of streams per unit area. Any attempt to calculate drainage density is impeded by the difficulty of calculating total stream length, as the exact point at which a stream starts is problematical. See Lin and Oguchi (2004) Geomorph. 63, 3–4. Since water flow in channels is faster than overland flow and throughflow, the higher the drainage density, the faster the hydrograph rise, and the greater the peak discharge.