In order to analyse the drains, we need more than just lines on the map; we need the profile (shape), dimensions, depth, material type, and surface roughness of the drains. Furthermore, the hydrological modelling software requires that every single segment of the drain map be connected; nothing can be missed or inaccurately positioned.
Tunahitaji wasifu (Sura), vipimo, urefu, aina ya vifaa, na mwonekano wa mfereji. Hata hivyo programu hii ya hydrolojia inahitaji kila kipande cha mfereji kwenye ramani kiunganike, kisikosekane kitu na chochote kisikae vibaya (Kila kitu kikae kwenye sehemu yake ili kuwezesha programu hii kufanya kazi)