Drainage Systems for LBRC Training of Trainer Personnel on Environmentally Sound Design and Implementation of Public Works- Community Roads of the Productive Safety Net Program (PSNP)

Drainage Systems for LBRC  Drainage system is part of the road work intended to safely drain the flood water along, away or across the road structure  Road surface drainage system includes: 1.Camber of road or cross-sectional drain, 2.Road side ditches (trapezoidal, V-ditches), 3.Mitre drain (turn out ditch or option drain),

Drainage Systems for LBRC (cont’d) 4. Catch water drain (interceptor ditch), 5. Longitudinal gradient, 6. Scour checks (check dams), 7. Culverts, and 8. Fords (drifts or Irish bridge)

Drainage Systems for LBRC (cont’d) Details of the drainage system of LBRC 1.Camber of road:  Drain water to two sides of road on flat and rolling terrain,  Drain water to one sides of road on mountainous terrain &curve super elevation.

Drainage System for LBRC (cont’d) 2. Side ditches: we can have side ditches as  Two on flat terrain,  One on rolling and mountainous terrain,  None on embankment fill roads. 3. Mitre drain: we can provide mitre drain on  Two sides on flat terrain  One side on rolling terrain (and mountainous),  Angle from side ditch could be 30 degree or 45 degree

Drainage System for LBRC (cont’d) 4. Catch water drain: catches water upslope of the ditch from high level ground or slope 5. Longitudinal gradient: slope along the road to avoid stagnation of water on the surface 6. Scour checks: to reduce speed of water along the ditch. They have apron downslope & made of :  Wood (brush wood),  Stone or sand/soil filled sacks.

Drainage System for LBRC (cont’d) 7. Culverts (pipe, box, slab culverts. Pipe culverts are common (single, double, etc.)  Trench excavated to lay pipes,  Well-compacted foundation underneath,  Mortar-Jointed, fill around pipe and on top,  Depth of fill on top of pipe = ¾ pipe diameter, min ½ diameter 8. Fords: Flat bottomed, gentle slope approach, masonry upslope and downslope, stone apron and riprap

Drainage System for LBRC (cont’d) What if drainage system is poor? Negative effects will be caused like:  Poor camber results in pot holes and ruts,  Poor side ditches: high flow, scour & road failure,  Poor mitre drain: high flow in ditches, scour  Poor catch water drain: high flow in ditches, scour

Drainage System for LBRC (cont’d) What if drainage system is poor? Negative effects will be caused like:  Poor gradient: surface water stagnation, pot holes  Poor scour checks: ditch erosion and road failure  Poor culverts: lack of smooth water crossing  Poor fords: scour downslope of ford and road failure or breaking of ford, hence closure of road.

Drainage System for LBRC (cont’d) Generally, poor design of any drainage system may cause environmental destruction and road failure that finally result in complete closure of road and interruption of traffic, which is the opposite of an intended purpose of road construction.

Questions or comments from trainees or other trainers?

Training of Trainer Personnel on Environmentally Sound Design and Implementation of Public Works- Community Roads of the Productive Safety Net Program (PSNP) June 13-24, 2011 Ghion Ambassel Hotel Dessé, Ethiopia