The main trunk roads should be built to be weather-proof, meaning the level to which they must be constructed must be above the highest known flood level. 
Barabara kuu ni lazima zijengwe ili kuhimili hali yoyote ya hewa, kwa maana kwamba kiwango ambacho barabara hizo zitajengwa ni lazima kiwe ni kiwango cha kitachakowa juu ya kima chochote cha mafuriko.