FS

uplift and erosion form landscape

river is in equilibrium of transport cap and sediment supply

after disturbance: re-establishing of equilibrium

two models: progressive change, episodic change

rates of U(t) and e(t)

their temp variability

intermitency (periodizität)

prob dist of large events

feedbacks

FS is complex because:

processes act together

many timescales involved

adjustment take long and overlap

external and internal forces adjust the system

-> complexity = predictable??

system organises itself in a critical state

in the critical state, all seizes of events may occur

predictability is only in a mean statistical way possible

critical state is: an attractor, globaly stable, locally instable

stat properties of SOC are very similar to natur

does not work for all granular piles

based on efficiency of transporting sediment

local optimality: equal energy dissipation per unit channel

global optimality: minimal energy dissipation in total

-> very similar to natur

fully coupled, uncoupled, de-coupled

important: effectiveness, magnitude, direction of coupling

lateral: hillslope-channels

longitudinal: upstream-downstream

vertical: river-aquifer

disconnectivity: buffers, barriers, blankets

buffers: swamps, floodplains

barriers: steps, slugs

blankets: floodplains

boosters: gorges

sigma(r) = P(r)/T(r) = erosion-deposition/ transport capacity

if sigma ->0 : detachment limited

if sigma ->inf: transp cap limited

seasonality of hillslides and floods

landslide occur in winter -> sediment delivery

floods occur in summer -> transport of sediment

system responds to disturbence depending on its: state, connectivity, forcing

can be hyper- or undersensitive -> new or old equilibrium

reaction: disturbance - response of system

response: disturbance - new eq.

relaxion: time it takes to change to new eq

response = reaction + relaxion

they all depend on: state, connectivity and forcing of the FS

use of sediment continnuity/mass balance to compute channel change as a function of changes in the sediment transp flux

(1-p0) dz/dt = -dqs/dx, with p0 = V_water/V_total

used in erosion-deposition models

allows assessment of river straightening

effect of straigntehing of a river:

upstream: degradation z-

downstream: aggregation z+

qs: eincreased in straightened section

calculation: (1-p0)(z_t+dt -z_t) dx = (qs,x - qs,x+dx)dt

short term effect: higher flow velocity

long term effect: aggregation & degradation

conservation of mass

conservation of momentum

sediment continuity (exter)

+ q = q(v)

-> all eq interact

how to determine sediment transport? -> morphodynamics

v_x/u_* = 1/k*ln(z/z0)

derived from turbulent flows in open channels

res to flow: overland >> channel

due to: low flow depth, raindrops, vegetation (inc surf roughn, ext laminar flows, negates raindrops)

f=k_t/Re= (k0+Ai^b)/Re (laminar)

f ≈ 0.223/Re^0.25 (turbulent)

i = precipitation intensity

shields parameter is a critical value, where transportation e.g. incipient motion begins

tau. = hydrodyn. forces/rising forces = tau0*ds² / gamma_s*ds³-gamma_m*ds³ = rho_m * u.²/(gamma_s-gamma_m)*ds

= (F_lift + F_drag + F_rising) / (F_wweight + F_buoyancy)

only dealing with single grains

tau. = hydrodyn. forces/rising forces = tau0*ds² / gamma_s*ds³-gamma_m*ds³ = rho_m * u.²/(gamma_s-gamma_m)*ds

= (F_lift + F_drag + F_rising) / (F_wweight + F_buoyancy)

only dealing with single grains

multiple grain seizes -> partial motion

grain interaction

slope variation

geometry