POLLUTION OF COASTAL ZONES DUE TO DEFLECTIONS OF RIVERS UNDER THE INFLUENCE OF THE CORIOLIS FORCE Grigoriadou V., Konidaris A., Angelidis P., Kotsovinos N. Department of Civil Engineering, Democritus University of Thrace, V. Sofias 12, Xanthi 67100, Greece s:

Surface plume trajectory of river discharging into sea  Initial momentum at the estuary  Buoyancy forces due to the density difference of the sea ambient  Surface shear stress due to the winds  Geomorphology of the seabed  Coriolis force due to the earth’s rotation

Satellite image of North Aegean and Propontis (June 2003) (source: http//modis.gsfc.nasa.gov/)

motor Angular velocity control sensor cameras flow meter PC Observation platform 5.2m 1.0m 15cm Outflow pipe

 Usage of potassium permanganate (red colour)  Identical density for outflow & ambient water  Rotation of the basin for some hours before the experiment, for the ambient water to acquire rigid body form 30cm

26 experiments  Volume rate Q: 0.48 – 1.76 lt/min  Rotation period Τ: 30 – 90 s  Froude number: : 0.33 – 1.19  Rossby number: : – INERTIAL FORCES GRAVITY FORCES INERTIAL FORCES CORIOLIS FORCES

y max t/T=5.67

Behavior at the initial phase of the spread Dimensionless parametric equation of the trajectory (clotoid curve) : characteristic length : dimensionless distance along the trajectory J r : momentum flux at the orifice α : Valid for deep ambient (h/L > 0.2) x y

Comparison of an experimental trajectory at the initial phase of spread with the theoretical clotoid curve from Savage & Sobey. Q = 0.96 lt/min T = 60 sec L theor. = 0.44 m F o = 0.65 Ro = 0.08

y max t/T=5.67

F o < 1F o > 1 Correlation of the dimensionless maximum spread width and the Froude number

APPLICATION: calculation of the maximum spread width for flood discharge of Evros river Q = 3000 m 3 /s average estuary depth: 4m U o = 1.25 m/s estuary width: 600m 41 o north parallel Τ = 37 hr natural river α = 0.01 L = m Y Α = 0.8L = 9300 m F o = 0.2 Y max /Y A = 1.3 Y max = m using graph

CONCLUTIONS  The influence of the earth’s rotation (Coriolis force) on the spread of the large scale environmental flow was studied  A series of experiments with horizontal outflow in rotating ambient was performed  Deflection to the right of the outflow axes was observed  The theory of Savage & Sobey that at the initial phase the trajectory of the front follows the clothoid curve was validated  The existence of a maximum spread width, where the discharge water is restricted and remains for a long time was detected  A method for the calculation of the maximum spread width was suggested, as a function of the initial conditions: outflow velocity outflow momentum flux angular velocity ambient depth