the impact of tidal pumping, turbidity maxima, density ...the impact of tidal pumping, turbidity...
TRANSCRIPT
The impact of tidal pumping,
turbidity maxima, density
gradients on sediment
retention in estuaries
Dr Gerardo M. E. PerilloInstituto Argentino de Oceanografía
Departamento de Geología - UNS
Where sediment is trapped
• Estuarine deltas (head, tidal, tributarymouths)
• Inner wetlands (mangroves, marshes,tidal flats)
• Point and interchannel bars
• Other geomorphologic andhydrodynamic induced traps
• Artificial structures (harbours, jetties,etc.)
What traps sediment
• General and local geomorphology
• General and local sediment inputs
• Within-estuary tidal range gradients
• Tidal pumping
• Turbidity maxima
• Vertical and longitudinal density gradients
• Coastal dynamics
• Climate dynamics
• Events
• Biological interactions
However!!!!
• Sediment and water input from rivers
– What happens with dams and watershed
retention??
– How much sediment is retained in lower
catchment (below the last gaging station)
• Sediment input from the sea
– Barrier effects (i.e., tidal deltas, barriers)
Lack of input implies internal erosion and
sediment export
• Ratio ocean vs
continental E.
• Sediment input
• Coastal stability
• Climatic regions
0 2 64
Deltasfluviales
Barreras
Deltas ddemarea
Bocas demarea
Bancosalineados
Planicies de marea
Marismas
Micromarea l Mesomarea l Macromareal
Amplitud de marea (m)
-59 -58 -57 -56 -55
Longitud
-36
-35
La
titu
d
10
8
6
8 2030
35
20
25
20
30
40
50 55
20
15
10
8
6
10
10
8
15 20
25
15
6
25
U R U G U A Y
A R G E N T I N A
MontevideoBuenosAires
La Plata
Colonia del Sacramento
Pir
iápo
lis
P. d
el E
ste
P. Rasa
P. Piedras
P. T
igre
Canal M
arítimo
Banco
Ro u
en
Bar
ra d
el In
dio
BancoArquímedes
Banco Inglés
Canal Oriental
Bahía deSamborombón
Antico, 2002
Antico, 2002
0.E+00
1.E-04
2.E-04
3.E-04
4.E-04
5.E-04
6.E-04
7.E-04
8.E-04
0 50 100 150 200 250 300
x ( km )
Gx
( m
2 s-3 )
Gx media
Gx máxima
Gx máxima - Gx media
0 20 40 60 80Distance from head (km)
0
4
8
12
16
Gx/G
0
ENERGY DISSIPATION
Río de la Plata – Antico, 2002
Bahía Blanca Est.
Perillo & Piccolo, 1991
TIDAL ASYMMETRY
Fluvial effect on the tidal
range.
- Increase inland
- Changes in tidal asymmetry
- Potential sediment outflow
Kimmerer WJ. 2004.
http://repositories.cdlib.org/jmie/sfews/vol2/iss1/art1
San Francisco Bay
Headward influence increase
A.D. Heap et al. /
Sedimentary
Geology 168 (2004)
1–17
A.D. Heap et al. /
Sedimentary
Geology 168 (2004)
1–17
J.O. Blanton et al. / Estuarine, Coastal and Shelf Science 57 (2003) 993–1006
Wurpts, 2006
SALT WEDGE (A)
FJORD
PARTLY MIXED (B)
VERTICALLY HOMOGENEOUS
Residual Fluxes
Interaction with
• Estuarine Geomorphology
• Density gradients
• Wind
• Freshwater discharge
uL = uS + uE
Lagrangean Flux = Stokes Drift + Eulerian Flux
Stokes Drift (uS)
• Interaction between the partly
progressive tidal wave and the
topography
• Headward
• Associated to Tidal Pumping
uAu
AS=< >
< >
~~
Eulerian Flux (uE)• Response to the set up induced by the
tidal pumping
• By continuity generates seaward flow
<QE> = -<QS> uE = <Au>/<A>
• Valid for steady state
• Without river discharge
Lagrangean Flux (uL)
• Transport due to density gradient
uL= <Qvt>/<A>
• River runoff (uf)
uf= <Qf>/<A> <Qf>=R
uL = uf
In steady state, near the head
Residual Flux Calculation
Datos Ui,j,k ; Si,j,k ; Ci,j,k ; Ai,j,k
Donde i = total # of levels …. I ; j = total # of columns…. J; k = time k = 0, 1, …, n k = T
F uCdA=
F IJUCA J A u c I A u c Fvtk i i
i
j j
j
= + + +• • • •
*
Where
FL = FTP + FVS + FTS + F*
F A u s
F A u s
vs i i
i
ts j j
j
=
=
• •
• •
F Q C
F QC
L
TP
=< >< >
=< >~
CONCLUSIONS
• Hydraulic processes are key to
sediment retention/export in estuaries
• Geomorphology is as or more
important
• Some processes have been considered
only for the whole system or in
individual portions of some estuaries