World Bank 11/2/2019 GUIDELINE: GREEN ROADS FOR WATER ROAD INFRASTRUCTURE IN SUPPORT OF WATER MANAGEMENT AND CLIMATE RESILIENCE Authors: Frank van Steenbergen, Taye Alemayehu, Kifle Woldearegay and Marta Agujetas Perez www.metameta.nl www.roadsforwater.nl correspondence: [email protected] Dedication to Ian Neal, who is no longer with us in person, yet in spirit is. Ian catalysed much of the early thinking on ‘roads for water’. Table of Contents Executive summary ............................................................................................................................................................. 6 1. Introduction ................................................................................................................................................................ 9 1.1 Objective ................................................................................................................................................................. 9 1.2 Opportunities ....................................................................................................................................................... 10 1.3 Promoting resilience: three levels .................................................................................................................... 11 1.4 Costs and benefits .............................................................................................................................................. 14 1.5 Organization of the Guidelines ....................................................................................................................... 15 2. Roads for Water Harvesting in Semiarid Areas .................................................................................................. 19 Key message ............................................................................................................................................................... 19 2.1 Objective .............................................................................................................................................................. 19 2.2 Opportunities ....................................................................................................................................................... 20 2.3 Recommended practices .................................................................................................................................... 24 2.3.1 General principles ..................................................................................................................................... 24 2.3.2 Techniques for road-water harvesting ................................................................................................... 25 3. Roads for Watershed Management ...................................................................................................................... 36 Key message ............................................................................................................................................................... 36 3.1 Objective .............................................................................................................................................................. 36 3.2 Opportunities ....................................................................................................................................................... 38 3.3 Recommended practices .................................................................................................................................... 38 3.3.1 Choosing the location and slope of road .............................................................................................. 38 3.3.2 Designing the road drainage system ..................................................................................................... 41 3.3.3 Planning water harvesting and erosion control measures along with roads .................................. 45 4. Roads for Water in Coastal Lowlands ................................................................................................................... 48 Key message ............................................................................................................................................................... 48 4.1 Objective .............................................................................................................................................................. 48 4.2 Opportunities ....................................................................................................................................................... 49 4.3 Recommended Best Practices ........................................................................................................................... 50 4.3.1 Roads for water management in low-lying coastal areas ................................................................. 51 4.3.2 Roads combined with flood embankments ............................................................................................ 58 4.3.3 Roads as temporary flood shelters and evacuation routes ............................................................... 62 5. Roads for Water in Mountain Areas ...................................................................................................................... 65 Key message ............................................................................................................................................................... 65 5.1 Objective .............................................................................................................................................................. 65 5.2 Changing the mountain environment ............................................................................................................... 67 5.3 Improving the mountain road ........................................................................................................................... 69 5.3.1 Choosing the road alignment and design carefully ............................................................................ 69 5.3.2 Choosing appropriate construction methods ......................................................................................... 70 5.3.3 Including protected road water crossings ............................................................................................. 72 5.3.4 Managing roadside mountain springs and seeps ................................................................................ 74 5.4 Improving the mountain road environment .................................................................................................... 77 6. Roads and Rural Water Supply .............................................................................................................................. 83 Key message ............................................................................................................................................................... 83 6.1 Objective .............................................................................................................................................................. 83 6.2 Opportunities ....................................................................................................................................................... 83 6.3 Recommended Practices .................................................................................................................................... 85 6.3.1 Road water harvesting for groundwater recharge ............................................................................. 85 6.3.2 Road water harvesting for surface storage .......................................................................................... 87 6.3.3 Using springs opened by road construction .......................................................................................... 89 7. Borrow pits .................................................................................................................................................................. 96 Key message ............................................................................................................................................................... 96 7.1 Introduction ........................................................................................................................................................... 96 7.2 Opportunities ....................................................................................................................................................... 96 7.3 Recommended practices .................................................................................................................................... 99 7.3.1 Siting of borrow pits .................................................................................................................................. 99 7.3.2 Size and shape of borrow pits .............................................................................................................. 101 7.3.3 Ensuring the safety of the converted borrow pit ................................................................................ 103 7.3.4 Reducing excessive seepage ................................................................................................................. 104 7.3.5 Reduce the risk of sedimentation .........................................................................................................