Overbank flow
|
Low frequency of occurrence
(only for the highest tides)
Relatively shallow water depth
(\(Y_{\text{MAX}}\)<1 m)
Weak and frictionally-dominated flow
(\(v_{\text{MAX}}=\)0.1-0.2 m/s)
Flow direction nearly perpendicular to the channel-axis
orientation
|
High frequency of occurrence
(almost every tidal cycle)
Relatively large water depths
(\(Y_{\text{MAX}}\)>3-4 m)
Strong and sheet-flow-dominated flow (\(v_{\text{MAX}}>\)0.4-0.5m/s)
Flow direction virtually unrelated to the channel-axis orientation
|
Stage-velocity relation |
Higher velocities for above-bankfull stages
(\(Y\)>\(Y_{B}\)) |
Higher velocities for below-bankfull
stages (\(Y\)<\(Y_{B}\)) |
Secondary circulations
|
Relatively strong
More pronounced when primary streamwise flows are stronger (i.e., in
phase with streamwise flows)
|
Relatively weak
More pronounced when primary flows are weaker (i.e., out of phase with
streamwise flows)
|
Helical flow |
Well developed |
Poorly developed |
Flow separation |
Possible as a function of bend geometry and tidal flow
characteristics (i.e, Froude number) |
Possible as a function of bend
geometry and tidal flow characteristics (i.e, Froude
number) |
Rainfall runoff |
Limited importance due to the presence of vegetation |
Potentially significant due to the absence of vegetation |
Wave action on intertidal plains |
Weak due to wave attenuation by
vegetation |
Strong due to high overbank water depths and reduced
friction |