In reclamation areas drainage pipes are usually laid at flatter gradients when compared with upstream stormwater pipes. The fact that the nature of flow in stormwater drain is by gravity makes the downstream pipes in reclamation areas relatively deep below ground surface. It is preferable to have outfall of drains above the tidal influence level and this accounts for the relative flatter gradient of drain pipes in reclamation area.
Attention has to be paid to the possible occurrence of differential settlement in reclamation area. For pavement design, flexible pavement is preferred to rigid pavement to cater for settlement problems. Similarly, in the design of drains flexible joints like spigot and socket joints and movement joints in box culverts have to be provided to guard against the effect of differential settlement.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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