Monitoring the lateral channel movements on the alluvial fan of Wadi Feiran drainage basin, South Sinai, Egypt using multi-temporal satellite imagery

摘要

Human activities triggered various lateral channel movements over the alluvial fan of Wadi Feiran drainage basin, south Sinai, Egypt. Landsat TM images dated 1986, 1996, and 2001, along with a SPOT 4 XS image dated 2006 were acquired to monitor the lateral channel movement on the alluvial fan of Wadi Feiran through the last two decades. The lateral channel movements have been initiated by the channel avulsion of the incised channel of the alluvial fan as a result of obstructing the flow by developing a man-made barrier from the accumulated flood debris in the early years of 1990(s). The man-made barrier had evolved into an elevated concrete road of 3.75 m height with two culverts underneath directly south the fan apex by March 2007. These human activities enforced the incised channel to avulse in a new location leaving the original path and the active depositional lobe of the fan abandoned. Under the influence of successive flash flood events through the last twenty years, channel aggradations occurred resulting in channel braiding and channel widening processes in the reaches of the new formed distributary channels. The channel widening processes occurred on the expense of the inactive fan lobes located within and south the reaches of the new distributary channels. Observing the southward lateral growth of the reaches of the new formed distributary channels implies the possibility of forming a new active depositional lobe that could be merged with the abandoned depositional lobe of the fan.