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Taiwan River Response to Faulting (Fossil organic carbon export (Hilton…
Taiwan River Response to Faulting
Yanites Method
Worked out stream power required to facilitate the river downcutting observed
Modelled how landscape should've responded
Observed river ∆
lotsa downcutting & widening btwn faults
How river responded to Chi-Chi equake?
Cho Shui River
Briefly changed direction
Peikang
River
Upstream of Meiylan & Tili Faults
River adjusted to enhanced uplift via
both narrowing & steepening
∴ Direct river response to perturbation
as predicted by model
Sediment ∆ in river responding to uplift
Minimal in-situ sediment
Material delivered either via
landsliding
via river
∴ landslides/vegetated debris everywhere
large boulders from main failure
vegetation stripped by displacement
Model river response to equakes
Yanites 2010
T1. Surface rupture - landsliding
Whole system downcuts & retreats upstream
Right after equake
T2
Proximal
KP propagates upstream
Distal
Channel widens (incision limited0
T3
Proximal
Bed alluviated - river widens
Distal
Bedrock incision restarts
T4
New equilibrium profile develops
Upper reaches steepen
∴ below fault reaches disequilibrium as reach = too flat
thus system migrates upcatchment
Implications exported material
Organic-rich debris exported
Material exported to ocean
--> following such big equake/uplift events
Can alter organic carbon export
∴ affecting carbon budget of oceans (locally if not globally)
Fossil organic carbon export
(Hilton 2010)
Export to ocean from Taiwan after big equake
Big flux westward discerned from region where Chi-Chi equake occurred
Also big flux from SE
Whereas Northward export = much lower
(background)
Higher POC fluxed out during typhoon
Typhoon Q vs particulate carbon
During typhoons
Huge increase sed flux & poc exported to ocean
No typhoon
relatively low (background) POC
Floods
Floods dominate erosion of particulate organic carbon