1. Water resources management: getting water where and when WE want it, not as it occurs naturally – mostly for agriculture, for 1000’s of years…

Definition:3 Dimensions of C21 River Management (2.0)

2. Hazard management: associated with river flooding, erosion, and river ‘instability’… especially since urban growth onto floodplains (Industrial Revolution):

– Tulla 1817 “as a rule no stream or river needs more than one bed”: start of engineered river corridors

3. Conservation management: preserve and restore rivers for ecosystem benefit, functional benefit, social and environmental justice. Since the 1960s-1980s

…as practices for 1. and 2. are usually well-established, C21 river management is frequently about how to modifypractices for managing water resources & hazards while integrating conservation goals…

Ph

oto

: PW

D

Ph

oto

: SW

S

Intl. Comm. on StratigraphySubcomm. on Quat. Stratigraphy

Smith and Zerder 2013 Anthropocene

Anthropocene context

• Partly a matter of definition…

• overwhelming?

• dominant?

• significant?

• ‘Great Acceleration’ since 1950s

(Co-)evolution of rivers in the Anthropocene?

In Fluvial Systems?

• Brown et al., 2017 ESPL: Answer: f (geomorphic system, size, relief, susceptibility to tectonic activity)

• … more evident in small- to medium-sized catchments

Need cumulative impact studies: very few multi-stressor, catchment-historical, spatially- and temporally-differentiated-response…

Benefits? Better understand cause-effect sensitivity, role of human agency, advise research priorities, aid management

A = Astronomical forcingG = Geophysical forcingI = Internal dynamicsH = Human activity

Gaffney and Steffan 2017, Anthropocene Review

‘Anthropocene equation’: rate change of Earth system

Human Causes of Change

Land use activities: deforestation

Channelisation

MiningRegulation

Urban development

Responses/effects

Area (km2)

Minimum 61

Maximum 1,020,000

25th percentile 602

Median 2,950

75th percentile 5,781

Cumulative impact studies: a meta-analysis

Year Year Timespan

Minimum 1100 1950 31

Maximum 1963 2015 850

25th percentile 1851 2000 72

Median 1878 2005 127

75th percentile 1932 2009 151Timespan of studies

Category Data source

Instrumented surveysRiver channel cross-sections, bed elevation surveys, bathymetry, floodplain topography

Instrumented time series records

Gauging station flow/sediment data, water levels, flood records, precipitation records

Numerical modelling Flow hydraulics, rainfall-runoff modelling

River channel mapping Field, bed sediment, habitat surveys (e.g., RHS)

Land surface mapping Topographical, historical, geological, land cover

Remotely sensed imagery Aerial, ground, LiDAR, satellite

Modified from Trimble 2008

How? Data sources in historical research

Category Data source

Historical records / contemporary records

Infrastructure construction dates, river engineering records, mining records, wildfire archives, survey notes, archives, agricultural surveys

Floodplain / palaeochannelsedimentology

Floodplain/palaeochannel sections, faciesinterpretation, sediment cores

Relative and absolute dating techniques

Geochemical, isotope analysis, radiocarbon dating, dendrochronology, lichenography, artefacts

Data sources, contd.

Modified from Trimble 2008

Intrinsic limits to historical reconstruction?

Comprehensiveness:

Research Resolution

Average Minimum Maximum

Sub-periods 2.9 1 5

Stressor scales 3.9 2 6

Total stressors 5.4 2 11

No. Reaches 12.0 (SD 12.1)

2 49

Study length (km)

Median 83.5Mean 143.5

5.5 900

(Figure in progress…!)

Reaches

Sub-periodsStressorscales

What does a multi-stressor study look like?Factors driving change

ATMOSPHERE

BASIN

RIPARIAN

REACH

LOCAL

LAND COVER

NETWORK

Stressor ‘Scale’ Stressor Frequency

What sort of response? Evolution

Reductions in discharge or

sediment load

Reduction in channel

activity rates / ‘less

complex’ channel forms

Increases in discharge or

sediment load

Increased rates of channel

activity

Changes in meander

geometry

Changes in bed sediment

River (co)evolution in the ‘late’ Anthropocene…(1880-2005)

Studies: global (esp. European)

Size: 3,000 km2 (600-6,000 km2) Length: 84 km (27-140 km)

Delineated reaches: 9 (4-12) Sub-periods: 3 (2-4)

In response to: 5.4 stressors at 4 scales

Flow or flood regime variability, bank protection, dam, instream mining, land use change, forest cover change

Have responded in: width, depth, channel pattern

By: channel narrowing (fluctuating with widening)

bed incision

reducing lateral activity

changing from braided to single-thread channel

reducing sediment flux and channel storage

…co-evolution with human activity

before

18501850 1855 1860 1865 1870 1875 1880 1885 1890 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

little change change to narrowing

aggradation & braiding incision armouring (conceptual model)

narrowing and incision (conceptual model)

narrowing of 35% abrupt flood wideningintense narrowing widening

peak narrowing, pattern change stable d/s

rapid narrowing negligible activity

no major narrowing trend

greater narrowing in headwaters

wandering little activity

narrowing of 66%, incision, esp. near mining sites

rapid meander wavelength, sinuosity increase most rapid width decrease, length increase (Fig 10)

rapid narrowing and braid loss upstream (text) stability (d/s?) Fig7

incision u/s, stable d/s

width decrease, sinuosity increase width homogenous

not certain whether to retain this as a 1830 start significant continuous width increase, bedload reduction

tributaries lost links with mainstem runoff, width decreases, braid loss u/s/, sinuoisty increase d/s

channel narrowed 45%, lost braids, incised

significant channel form and type changes

significant incision, continued narrowing u/s, widening d/s

major incision, expansion continued incision

cutoffs/straightening, expansion, bend adjustment incision, low flow realignment below dam in unconfined channels

greatest rates of incision, narrowing d/s

bank erosion rates highest

When did change occur? …greatest intensity ‘Great acceleration’ since 1950?

Downs and Piégay, in preparation

An Anthropocene for the SCR?

Overwhelming impact of the

‘Great Acceleration’?

Downs et al. 2013

River co-evolution in the ‘late Anthropocene’?

C20 river systems subject to multiple

‘stressors’ got:

• narrower

• incised

• reduced lateral activity

• simplified channel patterns

An icon of the Anthropocene?

…implications for ecological

functioning and river conservation?

Gaffney and Steffan 2017

f (H >> A, I, G) ?

Implications for science and management

A role for a methodologically distinct

‘Anthropocene-scaled’ fluvial

geomorphology?

Studies in co-evolution: background

for developing river management 3.0?

…background to this workshop!!