Micro Drainage supplies industry standard sustainable drainage and flood
hazard software for the civil engineering and environmental sectors

• Assume runoff coefficient of 100% for roofs, roads (including verges) and other hard-standing areas. (2.6, 4)
• Additional 10% increase to paved areas for future urban expansion. (2.6, 5)
• Minimum velocity in sewers of 1 m/s at pipe-full flow. (2.6, 15)
• Roughness value (Ks) for surface water sewer design of 0.6mm. (2.6, 17)


• Minimum cover of 1.5 m for sewers laid in roads. (2.18, 1)
• Minimum cover of 1.2 m for sewers not laid in the road. (2.18, 2)
• Minimum size of a gravity sewer is to be 150 mm internal diameter. (2.19, 1)

Complete the pipe design in System 1. System 1 allows additional percentage in Global Variables and the powerful optimise function allows you to design to meet all the necessary criteria.