The oval shaped Kathmandu valley stretches 30 km EW and 25 km in NS direction encompasing an area of about 647 sq. km. The valley is drained by 10 different tributaries of the Bagmati river forming a typical Centripetal drainage system. The drainages consisting of Dhobi khola from Shivapuri Range, Bishnumati khola from Shivapuri and Nagarjung ranges, Hanumante and Manohara kholas from Nagarkot range, Nakhu, Kodku and Godawari Kholas from Phulchowki range and Balkhu and Bosan kholas from Chandragiri range, have originated from different directions. Bagmati, Dhobi, Balkhu and Bosam kholas form the 4 th order network whereas the remaining drainages form the 5 th order network and the Kathmandu Valley as a whole is taken into the 6th order network.