CONTROLS ON BEDROCK CHANNEL INCISION ALONG NAHAL-PARAN, ISRAEL

Nahal Paran drains 3600 km(2) of Egypt's Sinai peninsula and Israel's Negev Desert. Much of the channel is alluvial but a canyon 10.5 km lon g has been incised into Late Cretaceous chert and dolomite in the lowe r portion of the basin. Slackwater deposits and paleostage indicators preserved within the canyon record approximately 10 floods of 200 to 2 500 m(3) s(-1) over a period of at least 350 years. Step-backwater sim ulations of hood-how hydraulics indicate extreme Variations in stream power per unit area along the length of the canyon, and associated var iability in energy expenditure and sediment transport. These variation s reflect channel cross-sectional morphology. The greatest values of s tream power occur along the lower half of the study reach, in associat ion with three pronounced knickpoints and an inner channel. The locati ons of these features reflect the exposure of thick, resistant chert l ayers along the channel. The presence of several similar, but buried a nd inactive, knickpoints along the upper study reach indicates that th e locus of most active channel incision has shifted with time, probabl y in response to baselevel changes associated with tectonic activity a long the Dead Sea Rift. Thus, the rate and manner of channel incision along the canyon of Nahal Paran are controlled by lithologic variabili ty and tectonic uplift as they influence channel morphology and gradie nt, which in turn influence hydraulics and sediment transport.