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Flashcards in Reading Deck (17)
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1

Wohl 2004

- To make informed decisions on rivers, its important to think of them in terms of form and function
- Rivers 'also reflect people's history'
- 800AD = planting maize and deforestation have affected floodplains (also led to increase in sediment and water yields)

2

Newson 1997

Effective river channel management must be holistic at the catchment scale
- Improving river conservation must focus on increasing public awareness (better management = better knowledge of fluvial geomorphology)
- In LR after modification rivers will change their elevation, planform and inter-relationship with the flood plain

3

Hobbs and Hams 2001

Effective restoration requires ongoing dialogue between the general concepts associated with system behaviour and the specific practical restoration activities

4

Sclafani 2015

Erosion from debris avalanche into the Toutle River continues to produce a problematic quantity of sediment for downstream communities
- High level of uncertainty in the future of the Toutle Basin

5

Nygaara 2015

Since the 1980 eruption, the US army corps of engineers have been actively managing debris avalanche sediment in the Toutle River and lower Coulitz River

6

Newcomb and Flagg 1983

Eruption of Mt St Helens in southwestern Washington resulted in airborne volcanic material being deposited in many areas in the Pacific Northwest
- Toutle River basin was covered with volcanic ash and mud slides
- Heavy sediment loads in the Toutle River were carried downstream through the lower Coulitz river

7

Gregory 2006

Human activity affects river channels through engineering including channelisation, dam construction, channel diversion, etc
- Human role in changing river channels has been exorcised for more than 4000 years

8

Knighton 1998

Causes of change:
- long-continued evolution of the fluvial system
- Climate, vegetation, land use and base level = all major causes of instability in the fluvial system

9

Knox 1972

Climate impacts
- Results of study emphasise the importance of climate and land use to the biographic balance between runoff and sediment yield
- Morphology of stream channels and floodplains is controlled by physical environment of the contributing drainage basin
- Climate influences vegetation which influences watershed runoff and sediment yield

10

Newson 2007

A central concept in fluvial geomorphology is scale
- Rivers need both huge multi-disciplinary scientific effort and simple, careful and informed observation

11

Brighton 1998

- Rivers transport on average 19,000 million tonnes of sediment every year (80% solid and 20% dissolve)
- Humans becoming more influential due to regulation and changing and use patterns (e.g. 36,000 dams worldwide)

12

Knighton 1998

Overpopulation is biggest threat to fluvial systems

13

Wohl 2014 (overland flow)

Hortonian overland flow = infiltration capacity low compared to precipitation intensity
Saturation overland flow = direct precipitation onto saturated areas and return flow from subsurface as saturation occurs (antecedent conditions important)

14

Wolman and Leopold 1957

Bankful discharge = the state just before flow begins to overtop the banks
- Can also be based on recurrence interval (every 1-2 years tankful discharge is reached) (Wohl 2014)

15

Wohl 2014

Lane's balance = model of channel adjustments
QwS (proportionate to) QsDs

16

Lane's balance negatives

The form of a river is a consequence of way more processes than just changes in slow, discharge, sediment size or or volume.
Rivers are highly complex systems influenced by manifold factors = e.g. importance of flora (riparian veg) and sauna (all animal species in/around river)
Confinement of river system too (e.g. closed or coupled) and global climate change, natural hazards and human alterations alter fluvial processes within rivers and change whole morphology of the river.

17

What is Lane's balance?

Lane's stability concept equates the product of a river's sediment load and sediment size with the product of the same river's slope and discharge.
- when sediment load or size are disrupted, the balance with Stream slope and discharge is offset, and the imbalance may result in Aggradation or Degradation problems.