Environmental Engineering Reference
In-Depth Information
Top-soil
Sand
Gravel
Fig. 10.6. A French drain.
in the humid tropics, where rains are heavy, the drainage system should
absorb excessive surface water within minutes. Therefore, traditional
pipe drains should be avoided; drains should be closer together than
the commonly recommended 50 cm; or the so-called
French drains
(Fig. 10.6) should be used. French drains do not rely on pipes but rather
on carefully constructed beds of gravel, which draw water away quite
quickly and efficiently. Again all types have advantages and disadvan-
tages, so an experienced drainage engineer should make recommenda-
tions based on specific local conditions.
Cynodon, the best choice for rugby fields, should also be used for
football and hockey fields. It is the only species suitable for tropical
climates that tolerates the traffic associated with these games, recuperates
from injury quickly and provides a decent playing surface, although
some faster-growing varieties of zoysia grass could be considered on
school fields used predominantly by children.
On football and hockey fields, as on rugby fields, intense fertilization
is necessary. Urea, the primary source of nitrogen, should be applied
monthly at a rate of 0.5 kg of nitrogen per 100 m
2
or biweekly at 0.25 kg
