Amplified erosion above waterfalls and oversteepened bedrock reaches

نویسندگان

  • I. Haviv
  • Y. Enzel
  • K. X. Whipple
  • E. Zilberman
  • J. Stone
  • A. Matmon
  • L. K. Fifield
چکیده

, where E(x=La) is the erosion rate at the upstream end of the flow acceleration zone above a waterfall, Fr is the Froude number at this setting, and n ranges between 0.5–1.7. This amplification expression suggests that erosion at the lip could be as much as 2–5 times higher relative to erosion at a normal setting with identical hydraulic geometry. Utilizing this erosion amplification expression in numerical simulations, we demonstrate its impact on reach-scale morphology above waterfalls. Amplified erosion at the lip of a waterfall can trigger the formation of an oversteepened reach whose length is longer than the flow acceleration zone, provided incision wave velocity (Vi) at the upstream edge of the flow acceleration zone is higher than the retreat velocity of the waterfall face. Such an oversteepened reach is expected to be more pronounced when Vi increases with increasing slope. The simulations also suggest that oversteepening can eventually lead to steady state gradients adjacent to a waterfall lip provided Vi decreases with increasing slope. Flow acceleration above waterfalls can thus account, at least partially, for prevalent oversteepened bedrock reaches above waterfalls. Using the cosmogenic isotope Cl-36, we demonstrate that incision wave velocity upstream of a waterfall at the Dead Sea western escarpment is probably high enough for freefall-induced oversteepening to be feasible.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

The role of waterfalls and knickzones in controlling the style and pace of landscape adjustment in the western San Gabriel Mountains, California

Bedrock rivers set the pace of landscape adjustment to tectonic and climatic forcing by transmitting signals of base-level change upstream through the channel network and ultimately to hillslopes. River incision is typically modeled as a monotonic function of bed shear stress or stream power, modulated by sediment tools and cover effects, but these models do not apply in channels with steep or ...

متن کامل

Formation of waterfalls by intermittent burial of active faults

Waterfalls commonly exist near bounding faults of mountain ranges, where erosional bedrock catchments transition to depositional alluvial fans. We hypothesize that aggradation on alluvial fans can bury active faults, and that the faults accumulate slip in the subsurface to produce a bedrock scarp. Following entrenchment of the alluvial fan, the scarp can be exposed as a waterfall. To explore th...

متن کامل

Two-stage opening of the Dover Strait and the origin of island Britain

Late Quaternary separation of Britain from mainland Europe is considered to be a consequence of spillover of a large proglacial lake in the Southern North Sea basin. Lake spillover is inferred to have caused breaching of a rock ridge at the Dover Strait, although this hypothesis remains untested. Here we show that opening of the Strait involved at least two major episodes of erosion. Sub-bottom...

متن کامل

Downstream variations in the width of bedrock channels

Field surveys of channel width w and drainage area A in bedrock channel reaches reveal relationships where w 5 cA, similar to the classic hydraulic geometry of alluvial channels. Data from five mountain channel networks support the assumption used in many landscape evolution models that an alluvial hydraulic geometry relationship where b 5 0.3–0.5 holds for bedrock channel systems. Although the...

متن کامل

Managing pH of Muck Soils for Vegetable Production

Historically, the Everglades Agricultural Area (EAA) evolved under seasonally-flooded conditions that predominately supported sawgrass and other wetland vegetation. Over several thousand years, Histosol “muck” soils were deposited as organic matter accumulated above the limestone (calcium carbonate) bedrock. In the early 1900s, these soils were drained. Declining water table levels coupled with...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2006