Coupled Morphodynamic-Physical
Habitat Modelling: MORPHED |
Introduction to Morphodynamic Modelling: |
Morphodynamic models and Landscape Evolution Models
(LEMs) simulate the geomorphic response (typically of a catchment
or a channel reach) to certain drivers (usually a minimum of climate
and topography). The landscape (inclusive of a river channel) is represented
with a topographic model, and at every time step a new topographic
model is produced representing the products of erosion, deposition
and storage.
Such models come in a variety of forms (see
here for links to models), which are normally dictated by the
model developer's research interests and coding experience. The distinction
between morphodynamic models and LEMs is vague, but has largely to
do with the temporal and spatial scope of the modelling. The term
LEM implies modelling geomorphic evolution over longer time scales
(e.g. 100's to 1000's of years) and does not necessarily include a
hydraulic solution; whereas morphodynamic models often focus on the
dynamics produced by individual hydrologic events over time-scales
of hours to tens of years.
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Belief in Importance of Geomorphic Dynamics to Fish: |
There is a
wide spread belief that the quality of physical habitat (for both
flora and fauna) in riverine environments is a direct product of
geomorphic
dynamics and natural variability of flows. Morphodynamic models fully
coupled to simple vegetation regeneration and growth models have been
in circulation for at least a decade. The quality of physical habitat
for fish in response to hydraulic and hydrologic variability has been
studied and modeled extensively (ecohydraulics).
However, we know of no examples of a fully coupled morphodynamic model
to an ecohydraulic fish habitat model (please email
me if you know otherwise). Such a model could give significant
insight into the implications of geomorphic dynamics on physical habitat
quality. Among the key physical requirements of such a model are:
- Capability to assess fish habitat suitability changes through
time in response to both hydrodynamics and morphodynamics
- Produce a hydraulic solution (velocity and depth on a cell-by-cell
basis) good enough to drive sediment entrainment, sediment
transport, sediment deposition and an ecohydraulic fish habitat
model
- Produce a morphodynamic solution (i.e. mobile and changing bed)
with emergent properties of morphological unit preservation, persistence
and reproduction after destruction (i.e. dynamics of pool, riffle
and bar morphology appears geomorphicaly reasonable)
Initially, I attempted to modify the CAESAR
LEM (with the ooCAESAR project) to meet
the above requirements. Owing primarily to unrealistic preservation
and production of morphological units at a scale relevant to fish
(third bullet above), the simple modification of CAESAR proved unfit
for this purpose. As such, we have gone back to the drawing board
and are in the process of developing a model specifically geared to
meet the above requirements. Tentatively, I call it 'MORPHED' - Model
Of Riverine Physical
Habitat & Ecohydromorphic Dynamics.
As the model is fundamentally concerned with capturing changes (Δ)
and habitat dynamics defined by morphology, and the project itself
morphed out of the ooCAESAR effort, MORPHED is a dually appropriate
name. Details of the model will be forthcoming from this website.
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Collaborators and Researchers on this Project: |
| Dr. James Brasington (Aberystwyth) is my primary collaborator on this project. Other collaborators include my PhD supervisors Professor
David Sear (Southampton) and Dr.
Steve Darby (Southampton), and Dr.
Mike Bithell (Cambridge).
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Relevant References: |
- Cox C, Brasington J, Richards K, Wheaton JM and Williams R.
(Submitted). A Comparison of Cellular Automata Flow Routing Models.
Earth Surface Processes and Landforms.
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