Monitoring oil spill hotspots, contamination probability modelling and assessment of coastal impacts in the Caspian Sea using SENTINEL-1, LANDSAT-8, RADARSAT, ENVISAT and ERS satellite sensors

Figures & data

Figure 1. Geographic location of the Caspian Sea and oil and gas fields under the exploitation in the Caspian Sea.

Figure 2. (a) Visible and (b) invisible oil slick because of wind speed; (c) radar backscattering of oil slicks and (d) backscattering of entire radar image (SENTINEL-1).

Figure 3. Coverage of radar and optical satellite images in the Caspian Sea.

Table 1. Characteristics of satellite sensors and count of used satellite images.

Sensors	Mode	Resolution (m)	Swath width (km)	Band	Wavelength	Operative	Count of used images
SENTINEL-1	IW (Interferometric Wide)	20	250	C	3.75–7.5 cm	2014 – operating	12
RADARSAT-1	SCW (ScanSAR Wide)	100 × 100	450–500	C		1995 – operating	16
RADARSAT-2	SCW (ScanSAR Wide)	100 × 100	450–500	C		2007 – operating	10
ENVISAT	IM (Image Mode)	30 × 30	100	C		2002–2012	255
	WSM (Wide Swath Medium)	150 × 150	400				6
ERS-1	PRI (Precision Image Product)	30 × 30	100	C		1991–2000	20
ERS-2	PRI (Precision Image Product)	30 × 30	100	C		1995–2011	71
LANDSAT-5	TM (Thematic Mapper)	30	185	B1 – Blue, B2 – Green B3 – Red B4 - Near Infrared (NIR) B5 – Shortwave Infrared B6 – Thermal, B7 – Shortwave Infrared	B1 (0.45–0.52 µm) B3 (0.63–0.69 µm) B4 (0.76–0.90 µm) B5 (1.55–1.75 µm) B6 (10.40–12.50 µm) B7 (2.08–2.35 µm)	1984–2013	11
LANDSAT-8	OLI (Operational Land Imager)	30	185	B1 – Ultra Blue (coastal/aerosol) B2 – Blue B3 – Green B4 – Red B5 – Near Infrared B6 – Shortwave Infrared B7 – Shortwave Infrared B8 – Panchromatic B9 – Cirrus B10 – Thermal Infrared B11 – Thermal Infrared	B1 (0.435–0.451 µm) B2 (0.452–0.512 µm) B3 (0.533–0.590 µm) B4 (0.636–0.673 µm) B5 (0.851–0.879 µm) B6 (1.566–1.651 µm) B7 (2.107–2.294 µm) B8 (0.503–0.676 µm) B9 (1.363–1.384 µm) B10 (10.60–11.19 µm) B11 (11.50–12.51 µm)	2013 – operating	10

Figure 4. Data-processing workflow for oil pollution studies in the Caspian Sea.

Table 2. Multiresolution and spectral difference segmentation parameters.

Multiresolution segmentation						Spectral difference segmentation
Scale parameter		Shape		Compactness		Maximum spectral difference
Radar	Optical	Radar	Optical	Radar	Optical	Radar	Optical
30	100	0.1	0.1	0.5	0.5	3	30

Table 3. Bonn agreement oil appearance codes (Bonn Agreement Aerial Operations Handbook 2009).

Appearance	Quantity (m^3/km^2)	Thickness (µm)	Typical appearance
Sheen (silvery/grey)	0.04–0.3	0.04–0.3
Rainbow	0.3–5	0.3–5
Metallic	5–50	5–50
Discontinuous true oil colour	50–200	50–200
Continuous true oil colour	>200	>200

Figure 5. Overall distribution of oil spills and natural seepage slicks in the Caspian Sea.

Figure 6. Temporal repetition (frequency) of oil spills and natural seepage slicks in the Caspian Sea.

Figure 7. Heatmap of oil spills and natural seepage slicks in the Caspian Sea.

Figure 8. (a) Aerial view of the Oil Rocks Settlement; (b) Pirallahi and Chilov Islands; (c) repetition of oil spills associated with wells of Oil Rocks Settlement, Pirallahi and Chilov Islands and (d) sample aerial view of Bonn agreement oil appearance thickness codes (Bonn Agreement 2011).

Figure 9. (a) Water surface: probability of contamination (%); (b) water column: probability of contamination (%); (c) total contamination probability risk (%) and (d) graph of water surface, water column and total contamination probability.

Figure 10. (a) Caspian Sea bathymetry and general circulation of currents; (b) detailed snapshots of Caspian Sea Winds; (c) currents visualised in OSCAR for date and time of 2007-05-07 06:00 and (d) currents around the Oil Rocks Settlement, Chilov and Pirallahi Islands.

Figure 11. (a) Cross-validation of predicted contamination probability with overall boundary of detected oil spills in the Caspian Sea; (b) distribution of predicted contamination probability classes within overall boundary of detected oil spills from satellite images and (c) exponential regression between probability of oil contamination and temporal repetition of detected oil spills from satellite images.

Figure 12. (a) Land-use classes along the shoreline of the Caspian Sea in Azerbaijan; (b) shoreline contamination probability (%) and (c) maximum accumulated emulsion mass (tonnes).

Figure 13. (a) Kilometre range of environmental sensitivities and contamination probability; (b) distance of land-use classes within contamination probability >50%; (c) kilometre range of maximum accumulated emulsion mass (tonnes); (d) distance of predicted maximum accumulated emulsion mass within contamination probability > 50%; (e) validation of shoreline contamination probability with shoreline pollution frequency detected from satellite images.

Bonn Agreement Aerial Operations Handbook. 2009. [accessed 2017 Feb. 6]. http://www.bonnagreement.org/publications.

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Bonn Agreement. 2011. BAOAC Photo Atlas (Bonn Agreement Oil Appearance Code). http://www.bonnagreement.org/publications.

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