2.4 RIVER SYSTEMS
All rivers flow from high ground to lower
ground. Few rivers travel from their source (starting
point) to their mouth (end point) without being joined
by other streams and rivers. A number of streams and rivers which
join together and then enter the sea (or a lake) in one channel
is called a river system. The area which they drain is
called their catchment area (see Map 2.4a).
Where river systems flow away from an area of high ground between
their sources, the high ground is called a watershed (see
Map 2.4a).
eg Map 2.4a River systems, catchment areas and watersheds.
This map shows eight river systems lettered
A -H. The line of watershed has been partly drawn on this map
by a dotted line.
(1) - use the same symbol to complete the watershed on this map
so that all eight river systems are separated from each other.
(2) - colour in blue river systems B and D.
(3) - colour in green the catchment area of river system G.
River systems show certain patterns :-
dendritic pattern - where rivers flow over a large area of the same rock type, the system looks like the trunk and branches of a tree (see Diagram 2.4b and try to find a similar drainage pattern on a physical map in your atlas).
radial pattern - where the rivers flow away from a central area of high ground eg The Lake District (look this area up on a physical map in your atlas and compare it with Diagram 2.4b).
trellised pattern - some rivers flow where alternate bands of soft and hard rocks reach the surface (see Diagram 2.4b). Such rivers generally flow along the bands of soft rock and in some places may cross the bands of hard rock at right angles eg in areas of clay vale and limestone escarpment (tilted upland).
Diagram 2.4b Patterns of river systems
