Exner conservation of bed sediment
For a constant-width reach with constant bed porosity p, sediment-solid conservation gives (1−p)Bη_t=−∂Q_s/∂x.
Key knowledge
For a constant-width reach with constant bed porosity p, sediment-solid conservation gives (1−p)Bη_t=−∂Q_s/∂x. A downstream decrease in solid sediment flux deposits material and raises the bed; an increase removes material. Q_s is a solid volumetric flux, so a measured mass flux must be divided by an appropriate grain density before using this form.
Values and equations
(1−p)B∂η/∂t=−∂Q_s/∂x
- p
- bed void fraction 1
- B,η,x
- channel width, upward bed elevation and downstream coordinate m
- Q_s
- solid sediment volumetric flux m³ s⁻¹
- t
- time s
Conditions and scope
- Fixed channel width B, bed elevation η increasing upward,0≤p<1, no unaccounted lateral sediment source and the stated bed-storage model.
- If suspended-sediment storage, changing porosity/width, multiple grain classes or lateral exchange matters, include the corresponding inventory and flux terms. Conservation alone does not supply a transport-capacity or entrainment law.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the actual displayed Exner equation, width/elevation/porosity definitions and supply-versus-capacity explanation. Explicitly fixed Q_s as solid volumetric flux for dimensional consistency; no adoption of an unspecified software sediment-load unit or closure.
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Entry details
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