The morphological factor 20 mei 2019 The morphological factor Erik Mosselman Bring Your Own Model to the RiverLab Deltares, Delft, 9 May 2019

Long-term morphological developments Strategies to speed up computations: Hierarchical tree of processes Cor Flokstra: Delft3D-MOR Efficient computation of varying flow fields Bert Jagers and Mohamed Yossef: case management tool Morphological acceleration factor Dano Roelvink: Delft3D-FLOW with sediment online Now in Delft3D and Delft3D-FM

Hierarchical tree of processes (Flokstra) Steering module: Links modules for different processes Process may be executed: a fixed number of times or for a given time span or as long as a certain condition is not satisfied

Case management tool (Jagers, Yossef) Efficient computation of varying flow fields: Store flow fields for computed discharges in database Use stored flow field from database as a starting point when discharge re-appears

Morphological acceleration factor (Roelvink) Flow and morphology computed within the same module: Calculate the flow field present during a time step Δt Multiply the corresponding morphological changes by MorFac Proceed in time over a period MorFac × Δt

Morphological acceleration factor discharge hydrodynamic time discharge x 2 morphodynamic time

Morphological acceleration factor discharge hydrodynamic time discharge morphodynamic time

Morphological acceleration factor discharge storage hydrodynamic time discharge storage morphodynamic time

Morphological acceleration factor discharge hydrodynamic time discharge morphodynamic time

Morphological acceleration factor Squeezing of discharge hydrograph into shorter duration: Acceptable for long, slowly varying hydrographs quasi-steady flow negligible flood wave attenuation Caution for short, rapidly varying hydrographs unsteady flow significant flood wave attenuation

When does flood wave attenuation matter? Chézy’s law:

When does flood wave attenuation matter? Continuity: Advection-diffusion equation with celerity c = 3u/2 and diffusion coefficient D = q/2iw Linearization, co-ordinate system moving with celerity c and substitution of sinusoidal wave with length Lwave Result: relaxation equation for water depth (and level)

When does flood wave attenuation matter? Linear approximation:

When does flood wave attenuation matter? discharge time acceleration factor 1 time

But there is much more … Mart Borsboom

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