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)