AZTI-Marine Research, Herrera Kaia, Portualdea z/g, 20110 Pasaia, Spain

MODELLING THE DRIFT OF MARINE LITTER IN THE BAY OF BISCAY

L. FERRER O.C. BASURKOI. GRANADO

I. RUIZ A. RUBIOJ. MADER

M. NOGUES I. EPELDE P. LIRIA

I. DE SANTIAGOJ.L. ASENSIO

A. CABALLERO A. DEL CAMPO

1 DEFINITION OF THE PROBLEM TO BE SOLVED: DRIFT OF MACROPLASTICS

1 DEFINITION OF THE PROBLEM TO BE SOLVED: DRIFT OF MACROPLASTICS

1 DEFINITION OF THE PROBLEM TO BE SOLVED: DRIFT OF MACROPLASTICS

PLASTIC

BOTTLES:

DRY

WEIGHT

RANGE

0.33-0.5 L~

15 g

………….

1.5 L~

33 g

1 DEFINITION OF THE PROBLEM TO BE SOLVED: DRIFT OF MACROPLASTICS

THEY HAVE AN

IMPORTANT

EMERGED

PART

BUT

IT DEPENDS

ON EACH

SPECIFIC

OBJECT AND

ITS STATE OF

DEGRADATION

1 DEFINITION OF THE PROBLEM TO BE SOLVED: DRIFT OF MACROPLASTICS

THE BIG QUESTION:

HOW DO THESE FLOATING OBJECTS DRIFT?

COMPLEX ANWSER, TAKING INTO ACCOUNT THAT THE DATA WE USE

TO ESTIMATE THE REAL DRIFT COME FROM NUMERICAL MODELS AND

THERE IS AN IMPORTANT PROPAGATION OF ERRORS FROM THE

ATMOSPHERIC MODEL TO THE WAVE AND OCEAN CURRENT MODELS

2 METHODOLOGY: MODEL

THE SOLUTION SEEMS TO BE HERE:

CLOSER TO A WIND MODEL THAN AN

EKMAN MODEL AND SEEMS TO DEPEND

ON THE WIND VELOCITY, THEN WE

ASSUME THAT THE DRIFT VELOCITY IS AS

SIMPLE AS FOLLOWS:

U_drift = C_d * U_wind_c

C_d = DRAG COEFFICIENT

U_wind_c = WIND VELOCITY CORRECTED

WITH A DEFLECTION ANGLE

2 METHODOLOGY: MODEL

WRF (WEATHER RESEARCH AND FORECASTING MODEL) WINDS WITH

A RESOLUTION OF 12 km (MODEL RUN BY METEOGALICIA)

NUMERICAL SIMULATIONS

(FOR DRIFTERS WITH A DRY WEIGHT < 1 kg):

C_d = 0.01, 0.011, 0.012,…, 0.068, 0.069, 0.07

DEFLECTION ANGLE (MINUS: TO THE RIGHT) = 0, -5, -10,…, -35, -40, -45

TOTAL: 610 COMBINATIONS

2 METHODOLOGY: SMALL WOODEN BUOYS

DIFFERENT WEIGHTS (g): 800 – 1,200

HEIGHTS (cm): 7 – 8

2 METHODOLOGY: DRIFTING BUOYS

WEIGHTS (g):

184, 293, 377, 513

VOLUMES (mL): 775

HEIGHTS (cm): 9.3

WEIGHTS (g):

350, 561, 724, 975

VOLUMES (mL): 1,308

HEIGHTS (cm): 15.7

3 RESULTS

3 RESULTS

3 RESULTS

3 RESULTS

3 RESULTS

THE BEST RESULTS (TO IMPROVE):

C_d: [0.015 – 0.030]

Deflection angle: [0º – 25º]

3

3

THE BEST RESULTS (TO IMPROVE):

C_d: [0.045 – 0.06]

Deflection angle: [0º – 25º]

3

FROM THE ORIA RIVER MOUTH

(NOT STILL SIMULATED)

CALM WEATHER LOW VELOCITIES

SHORT TRAJECTORIES AND A POSSIBLE

PROBLEM: MARINE LITTER GROUPING

3 RESULTS

MARINE

LITTER

GROUPING

PHOTO FROM IRATI’S HOUSE (ZARAUTZ)

3 RESULTSNEAR

ZARAUTZ

15 APRIL 2018

13:00 GMT

KOSTASystem

(WWW.KOSTASYSTEM.COM)

3 RESULTSNEAR

ZARAUTZ

15 APRIL 2018

14:00 GMT

KOSTASystem

(WWW.KOSTASYSTEM.COM)

3 RESULTSNEAR

ZARAUTZ

15 APRIL 2018

15:00 GMT

KOSTASystem

(WWW.KOSTASYSTEM.COM)

3 RESULTS

ZARAUTZ

BEACH

8 MAY 2018

16:00 GMT

KOSTASystem

(WWW.KOSTASYSTEM.COM)

2 RESULTS

LA CONCHA

BEACH

5 JUNE 2018

18:42 GMT

4 CONCLUSIONS

-MORE THAN 95% OF THE BOATS AND BUOYS DRIFTED, ON AVERAGE, TOWARDS THE EAST, DEPENDING MORE ON THE CYCLONIC CONDITIONS (HIGHER VELOCITIES) THAN ON THE ANTICYCLONIC ONES (LOWER VELOCITIES).

-WE FOUND THAT IT IS A DIFFICULT TASK FOR MARINE LITTER (IN MANY CASES DRIFTING IN GROUPS: “MARINE LITTER GROUPING”) TO ENTER OR LEAVE THE BAY OF BISCAY, SUGGESTING THAT THE SOURCES OF LITTER ARE IN THE BAY.

-A SIMPLE AND DIRECT RELATIONSHIP BETWEEN THE WIND AND DRIFT VELOCITIES IS APPLIED, WHICH REASONABLY REPRODUCES THE DRIFT OF THE BOATS AFTER ADJUSTING WIND PARAMETERS. IN THE CASE OF THE BUOYS, IT IS MORE COMPLEX TO OBATIN A SATISFACTORY RESULT (TO CONTINUE THE SIMULATIONS).

5 FUTURE WORKS

-WE WILL INCORPORATE THE EFFECTS OF WAVES AND SURFACE OCEAN CURRENTS (OUTPUTS FROM NUMERICAL MODELS AND HIGH-FREQUENCY RADAR) AND OTHERS TERMS SUCH AS THE TURBULENT DIFUSSION.

-BUT AS THESE DATA DEPEND ON THE WIND, IT IS VERY POSSIBLE THAT THE SOLUTION OBTAINED DOES NOT IMPROVE THE PRESENT RESULTS, BECAUSE THE WIND MODEL ERRORS PROPAGATE TO THE WAVE AND CURRENT MODELS.

-MOREOVER, THE MODEL OBTAINED MUST BE USED WITH FORECAST DATA INSTEAD OF THE BEST DATA OF THE PAST IN ORDER TO STUDY ITS ACCURACY IN FORECAST MODE, I.E. IT WILL BE MORE DIFFICULT FOR THE MODEL TO WORK WITH GUARANTEES.

-USE LOWER WEIGHT DRIFTERS SIMILAR TO EMPTY PLASTIC BOTTLES.