NET FLOW STRUCTURE AT TIDAL INLETS
Possible Implications for Transport of
Dissolved and Suspended Matter
Arnoldo Valle-Levinson
Civil and Coastal Engineering Department
Amy Waterhouse’s PhD dissertation
WI Program Initiation Fund
Freshwater input
Salty water inflow
(near the bottom)
OUT
OUT
IN
OUT
IN
Wind-driven Flow (with no river input)
Average Tidal Flow (with no river input)
Net transport after one period (cycle)
Direction of propagation
Net displacement = Stokes drift (covariance between tide and current)
Animation taken from GREEN EARTH WORLD POWER (gewp.org)
Residual set-up
z
x
Gradients in tidal flow – tidal stress
y
x
U T = U Stokes + U gradients + U set −up
Theoretical results over
simplified bathymetry
UT = UStokes + U press grad + Utidal stress
St Augustine
Inlet
Feb 2, 2006
ADCP Profiles and CTD casts
Full tidal cycles
13 transect repetitions
St. Augustine Inlet
Pattern reinforced in tropical season
Jupiter Inlet
May 9, 2006
21 repetitions
OUT
Jupiter Inlet
Ponce de Leon Inlet
Florida
Florida
Intracoastal
Waterway
Prepared by Amy Waterhouse
Ponce de Leon Inlet
Prepared by Amy Waterhouse
Depth averaged (~3 mo.) residual flows
5 cm/s
Prepared by Amy Waterhouse
Tidally averaged: us & un [cm/s]
Into the inlet
Depth (m)
Depth (m)
Out of the inlet
Prepared by Amy Waterhouse
1st Survey
Tidally averaged: us & un [cm/s]
Into the inlet
Depth (m)
Depth (m)
Out of the inlet
Prepared by Amy Waterhouse
2nd Survey
Residual flow modulated by winds and spring-neap cycle.
Deep: Outflow
Shallow: Inflow
Prepared by Amy Waterhouse
Residual flow modulated by winds and spring-neap cycle.
Deep: Outflow
Shallow: Inflow
Prepared by Amy Waterhouse
Strongest magnitude of exchange occurs during spring tides
Strength of Exchange : Deep - Shallow
Prepared by Amy Waterhouse
Strongest magnitude of exchange occurs during spring tides
Strength of Exchange : Deep - Shallow
Prepared by Amy Waterhouse
Panama
City
River-influenced
Oct 18, 2007
Feb
, K14,
= 12008
Prepared by Amy Waterhouse
SUMMARY (1)
Density-induced exchange flow
out
oyut
in
St Andrews Bay
z
y
out
St Augustine (wet)
out
in
SUMMARY (2)
Net tidally induced exchange flow
out
St Augustine (dry)
& Jupiter
out
in
short
z
in
Ponce de León
in
out
long
y
(wide)
(narrow)
low
E
med
E
high
E
(looking into the estuary; orange is inflow;
white is outflow)
(wide)
(narrow)
low
E
med
E
high
E
(looking into the estuary; orange is inflow;
white is outflow; arrows are transverse flows)
•
CTD Casts - Sea Bird SBE19
Tropical Savannah
Arid Dessert Hot
Temperate Not Dry Hot Summer
Peel, M. C. and Finlayson, B. L. and McMahon, T. A. (2007). "Updated world map of the KöppenGeiger climate classification". Hydrol. Earth Syst. Sci. 11: 1633-1644.
Wind-induced exchange flow (seaward wind)
τ
out
in
out
z
out
in
y
SUMMARY
out
out
in
Tidally driven
residual
exchange
z
y
Exchange pattern (for ‘short’ basins) consistent with density-driven
Fortnightly modulation opposite to that in temperate estuaries