Chapter 3. Geomorphology
53
3.3
STREAM SYSTEM TYPES
Discontinuous Ephemeral Streams
Discontinuous ephemeral streams form a distinctive stream pattern charac-
terized by alternating erosional and depositional reaches (Fig. 12) (Schumm and
Hadley 1957, Patton and Schumm 1975, Bull 1997, Field 2001). The longitudinal
distribution of processes and morphologies along one discontinuity can be
repeated multiple times along a stream, with the length of individual
discontinuities ranging from 15 m to over 10 km, depending on drainage area
(Bull 1997).
Overland flow emanates from the unconfined sheetflood zones and aggrading
downstream ends of channels. The reconcentration of the overland flow creates
erosional knickpoints at the downstream end of sheetflood zones that migrate
Figure 12. Schematic plan view and longitudinal profile of a discontinuous
ephemeral stream system, showing the relationship between sheetflood
zones, depositional and erosional channels, overland flow zones, and bank
heights (not to scale). (Modified from Field 2001.)
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