Trellised and rectangular pattern is probably the next most common and extensive after dendritic pattern. It may be seen in belted structures or topographies. It is most common where structure and topography both may be belted, i.e., parallel ranges or ridges may alternate with lowlands giving rise to a series of parallel streams seated in the elongated or ‘longitudinal’ valleys.
Another set of streams following the general slope of the whole mountain is transverse to the above-noted longitudinal streams. This arrangement obviously means rectangular pattern. The net is said to be rectangular when the streams have relatively wide spacing. If the spacing is close, the pattern is called trellised. In Fold Mountains, the original beds might have been successively superjacent but folding throws them into waves of anticlines and synclines with dips transverse to the direction of folding and strikes parallel to it.
Subsequent erosion exposes the beds as alternate belts of hard and soft structures. This again helps in the parallelism of the streams while the transversely flowing master consequent s or antecedents across the fold system complete the rectangular or trellised pattern.
Trellised pattern will also be found in such areas where cuesta topography occurs. Such a phenomenon generally occurs in coastal areas where erosion after tilting may lead to the formation of hard beds as escarpments and soft beds as lowlands.