Prijedlog

Prema reljefnoj razgranatosti pojedinog dijela kanalizacijske mreže južnog ogranka zaključuje se da kolektor1 (0700mm ) prihvaća cca 60% ukupnog dotoka u KMO-2 što iznosi Qj= 0.6x356.82 = 214.09 l/s.

Judging from/Taking into account the catchment [area] topography of the specific part of the southern branch drainage network it is possible to conclude that the water collector #1 ...

here "reljefna razgranatost" means the "area from which water is collected, the drainage area as determined by the relief/shape of the landscape"

another option "the drainage basin as determined by the shape of the landscape";

the "branching" / "ragranatost" is the tree-like shape of the water flowing downhill to collection points (as in this graphic http://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Hyd...

Drainage basin
From Wikipedia, the free encyclopedia
"Catchment basin" redirects here.

A drainage basin or watershed (North American English usages) is an extent or an area of land where surface water from rain, melting snow, or ice converges to a single point at a lower elevation, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean. For example, a tributary stream of a brook that joins a small river is tributary of a larger river, which is thus part of a series of successively smaller area but higher elevation drainage basins (watersheds).

http://en.wikipedia.org/wiki/Drainage_basin