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Taiwan Debate (Typhoons Dadson 2004 (Average ~ 4 / year typhoons passing…
Taiwan Debate
Typhoons
Dadson 2004
Average ~ 4 / year typhoons passing over Taiwan
= Mega precipitation events
Direction/path varies
Dadson Findings
Areas receiving most precip from typhoons often = fastest eroding areas
Infer: climate = dominant control on erosion/exhumation ?
' Dead
zone'
little exhumation
also receives little typhoon rain
Taiwan Rivers
Rivers rise up to 8 m during full flow in summer
During summer moonsoon/typhoons
High transport capacity
∴ Can mobilise large rocks
However, most of year
Rivers = transport-limited
∴ lotsa sediment = sitting around
Sed Flux from Taiwan
= Seasonally-controlled by monsoon & typhoon
Monsoon
mobilises lotsa large clasts each summer
Typhoon
Extreme storm events mobilise huge clasts
Signal = superimposed atop background/monsoon
Several typhoons/year ∴ landscape constantly changing
Historical erosion rate
Estimated average erosion rate ~ 5 mm/yr
Based on 30 year sed flux data
Remarkably consistent w/exhumation rate
Climate & erosion
Studying long term relation climate & erosion
Can only analyse magnitude
--> cannot look @ seasonality
Could infer from modern climate
assumes climate constant since then
Climate def has effect
Generation/mobilising sediment
Steep, unstable topog
lotsa sediment in system
Mass wasting
∴ sediment = mobilised
triggered by equake shaking & high precip
Steep hillslope
Lotsa hillslopes > 40°
∴ relation exists between
River incision
Hillslope undercutting
Mass wasting - flux more sed into rivers
Interconnectivity
River
Excavation & removal of sed from channel system
Undercutting
of hillslopes
Mass wasting
of destabilised hillslopes
Flux more material into rivers
Drives further incision, restarting cycle