Geomorphology, river hydrology and natural processes (Steve Addy

51 Pages·2013·2.76 MB·English

Geomorphology, river hydrology
and natural processes
SNH Sharing Good Practice Event: Identifying and
planning river restoration projects
Strathpeffer, 24th September 2013
Steve Addy
Outline
Controls on channel morphology
Fluvial processes
Channel morphology variability
River types
Links to river ecology
Some definitions
Fluvial geomorphology
Fluvial: rivers and streams
Geomorphology: the study of landforms and the processes
that form them
Hydromorphology
WFD leglislative term that encompasses fluvial
geomorphology and hydrology (i.e. the physical factors that
govern river ecosystems)
Alluvial
Sediment moved and deposited by rivers
Why is fluvial geomorphology important?
• Fluvial forms and processes are recognised as a key
component of river systems in EU WFD and national
legislation
• River landforms and flows constitute the basic ‘physical
template’ that influences riverine biota
• Fluvial geomorphology input is needed for sustainable river
management and restoration
• For mitigating flood risk and geomorphic hazards
Channel morphology
Consists of 5 variables that are inter-dependent i.e.
change of one variable leads to change in others in
response to alteration of the fundamental drivers
Water and sediment inputs
Valley width
Width
Depth
Roughness
(sediment and
bedforms)
Channel pattern
(Church, 2006)
Scales of channel adjustment

(Buffington, 2012)
Boundary conditions: inherited topography,
geology and sediment sources
• Topography reflects millions of years of landscape
development
• Scottish landscapes have been conditioned by glaciation
and rivers are still adjusting to this legacy.
Boundary conditions: bed and bank material
Sparse vegetation, non- Dense vegetation, cohesive Bedrock banks
cohesive alluvial banks alluvial banks

Alluvial bed A l l u v i al bed B e d r o ck bed
Increasing channel boundary resistance
Boundary conditions: large dead wood
• Wood is an important component of natural river ecosystems
• Can create significant flow resistance (hydraulic roughness)
• Influence on sediment transport and river bed habitats
(Soulsby, 2006)