FS

bankfull: flow that fills channel just to the top of the banks

most effective: flow that transports the most sediment on the long term

channel forming: flow that would form the same channel as the natural flow hydrograph does.

-> they can all be the same, but do not need to...

structures that have similar patterns/ geometric characteristics over a range of scales

objects with identical propery scaled parts are identical to the original, they are scale invariant

D= lim(log(N(r)/log(r)), r->0

D=0 point, D=1 line, D=2 area

in reality often 1.1...1.3

river network often have 2 dimensions: D≈1.1 -> shape of individual streams on small scale

D≈2 -> representing branching character of the network

can be expressed by hortons law: D = log(Rb)/log(Rl)

perfectly scaling (e.g. koch curve)

have a unique fractal dimension

are absolute scale free

have a scaling range where this relation holds

e.g. rivers, coastlines

to describe river network structure

identifying if (mean dissipation rate)/(unit channel) = konstant, if yes-> optimal

omega = tau * v = (rho*g*Sf*Q)/Pw = konst

erosion/depositon form channel in such a way that transport capacity is equal in the system (on the longterm).

-> equilibrium which is never reached but channels are adjusting towards it.

usefull to identify streams/ sections that deviate from the "optimal state"

belonging to the bank of a river

traditional semi-terrestrial areas

influenced by freah water, extending from the edge of water towards the edges of upland communities

very dynamic, e.g. clearance by flooding -> regrowth or not if to dry/wet etc...

abiotic + biotic env, lotic, lentic, semi-lotic

exchange of water, sediment, energy, nutrients on 4 dimensions

interconnected corridors

food webs, habitats

clustering + dispersion of populations

needs: flood disturbance -> cleaning & newly deposited sediment -> regeneration

hydrology: variability in flow

physical env: amont, variability

biology: diversity

water quality: temp. pH, BOD

geomorphology: eg. sediment load

regular low to medium flows: maintain water table -> growth

periodic high flows: channel movement + sediment deposition -> regeneration sites

well timed high + low flows: in growing season -> delivery of seeds -> establishment

gently traped flows after peak: sucessfull seed establishment (1-2.5 cm/d)

no high flows during sexond half of growing season: no destruction of seedlings

open sites: no competition for pioneers

moist enough: rooting of seeds

near to water: moisture + organis debris

different sediments: niches, variation

5 critical components:

magnitude of flow

frequency of occurence of flow above a given magnitude

duration of flood, low flow etc

timing/predictability of flow: important for seeds

rate of change / flashiness: change a lot due to dams (dQ/dt)

allows management of physical processes/landforms

direct form of management

rather local effect only, does not fix the problem - just its effects

easy to controll

small consensus needed

cause + effects are obvious

usefull to threat sections only - e.g. between irreparable sections

increase roughness

setting back flood defense

re-connectin side arms

mimikry natural flow hydrograph

deposit sediment

managing vegetation + wood debris

sustainable solution

does fix the whole system

not very practical

difficult to predict impact

uncontrolled management: not aceptable to managers & owners

too many stakeholders: difficult for consensus

managing downstream of dams: e.g. recruitment box

managing water abstraction level: controll of timing, quantity, seasonality

managing sediment flux

allow landslides

assesment requires:

measure range of ecosystem attributes

identify value of it

compare restored- unrestored forest

compare with reference forest

+ monitoring!

variables that do not vary

measure: key physical processes

biological response

simple + practical

repeated + compared

rapide response

uniformity

threaholds

landscape evolution

complexity

self organized criticality SOC

optimality

process laws remain the same for past, present and future

narure of processes does not change, frequency distr does not change

system only responds when treshold is exceeded

external or internal thresholds

critical slope

meander cutoff

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

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