Sea pollution off the Belgian coast, in figures

Operational ship discharges off our coast

Since the start of air surveillance in Belgium, in 1991, the MUMM has systematically kept figures on sea pollution in Belgian and neighbouring marine areas as observed by aerial surveillance. In this way an extensive database of sea pollution over a period of 25 years has been compiled.

operational discharge


Operational oil pollution

An operational oil slick observed in a ship’s wake is an immediate indication of a likely violation of the international discharge standards for mineral oil under the terms of Annex 1 of the MARPOL 73/78 Convention. Research and experiments at sea have also shown that an observable oil trace at sea originating in a ship is always the result of a discharge in excess of the permitted concentration limit for oil. A recent statistical analysis of illegal oil discharges by ships over the years has shown that the number of observed operational oil discharges from ships off our coasts has fallen sharply.

A deeper analysis of these multi-annual data compiled by the MUMM quickly showed that this decrease was not the same for the number of discharges per year, the total polluted surface area and the total polluted volume. Furthermore, it was not so much a continuous decrease but one achieved in stages over the years. Two crucial measures have provided the most visible impact in the field. In 1999 the North Sea was recognised by the International Maritime Organisation as a ‘Special Area’ for oil discharges by ships, since which time the strictest international discharge standards have consequently applied. This suddenly reduced by one half the number of pollution incidents and also the polluted area after 1999. The total volume of oil observed also fell after 1999 but less strikingly. A second important policy measure was the approval of the European Directive on Port Reception Facilities, which was only fully implemented for European ports from 2004-2005. As of that point all sea vessels were obliged to discharge their oil waste residue at European ports of call, making it difficult for ships to then illegally discharge large volumes of oil at sea. The MUMM has shown that these policy measures had a clear impact in reducing large volume incidents of oil pollution. In the period after 2004-2005 the annual oil volumes observed fell significantly, by around 90%.

Annual number of observations of operational oil pollution
Annual number of observations of operational oil pollution made by the aircraft per flight hour, in and around Belgian waters from 1991 to 2015.

These recent analyses of the MUMM data therefore clearly show the positive effects of the many policy measures. Other actions no doubt contributed to this fall: the criminal prosecution of illegally discharging vessels, the deterrent effect of aerial surveillance and port controls, positive changes in training and in the awareness of sailors.

The number of operational oil discharges by vessels off our coast, and the related volumes, continue to fall. In 2015 for the first time not one incident of operational oil pollution was observed in or around Belgian waters. That year the surveillance aircraft was, however, out of action for extensive maintenance for almost six months, during which time the pollution control flights were carried out by a replacement aircraft (without sensors). The coming years should therefore show whether or not the problem of illegal oil discharges off our coast is under control.

Oil discharge


Other harmful liquids

Since 1991 the MUMM has kept a systematic record of observations of operational sea pollution incidents other than oil pollution, i.e. those caused by noxious liquid substances or NLS. They are often referred to as “chemical discharges”, but are not necessarily chemicals, because vegetable oils fall under the NLS category.

The applicable international discharge standards for harmful or 'noxious' liquids other than oil are laid down in Annex II of the MARPOL 73/78 Treaty. Unlike a visible oil slick, many of the observed operational NLS discharges by ships are legally authorised at sea. In determining whether or not a discharge of another noxious liquid constitutes a violation, it is not so much the visual characteristics of the liquid that are the deciding factor, but where and how the liquid was discharged from a vessel at sea: in or outside territorial waters? Below or above the waterline? Was the ship travelling at sufficient speed and is there sufficient water depth?

Unfortunately, our NLS observations have not shown the same positive trend as for oil. Indeed, the number of pollution incidents for other noxious liquids saw a slight increase, although it cannot yet be proven statistically. Belgium is not the only North Sea country to make this discovery. France and the Netherlands have also recently reported an increasing trend in chemical discharges by ships in their waters.

Other noxious liquid discharge

The MUMM data show that incidents of operational pollution involving other noxious liquids have been observed in fewer numbers than oil pollution over the years, and that the general problem of ship discharges off our coast is not on the pre-2000 scale. However, in 2012, for the first time, more cases of chemical sea pollution were recorded off the Belgian coast than oil pollution, a phenomenon which recurred in 2015. Given that chemical discharges are often permitted at a distance from the coast, the length of sea pollution by other noxious liquids seems to be more than double that by oil slicks. Chemical discharges from vessels in the North Sea are not, therefore, a problem to be underestimated but one that demands further, close monitoring at sea and at the quayside.

Annual number of observations of pollution by other noxious liquid substances
Annual number of observations of pollution by other noxious liquid substances (NLS) made by the aircraft per flight hour, in and around Belgian waters from 1991 to 2015.


Accidental sea pollution

The problem of accidental sea pollution by ships is not limited to operational ship discharges. The exceptionally busy shipping traffic in the Belgian section of the North Sea, the Strait of Dover and the presence of Europe’s two biggest ports, Rotterdam and Antwerp, the shallow sandbanks… these are all factors resulting in the area's international recognition as a high risk area for shipping accidents and accidental sea pollution. The historical list of shipping accidents off our coast shows that collisions in our area can often result in accidental damage to the environment.

Since 1991 the aircraft has successfully provided operational support in the form of aerial monitoring and air support for pollution fighting units during more than 20 different shipping accidents in Belgian and surrounding maritime areas. In each case an evaluation of the severity of the accidental pollution and the threat to the coast is made from the air. The aircraft has also made numerous flights to guide the pollution-fighting vessels to the larger areas of accidental pollution from the air.

In 1993, for example, the aircraft was used in the crisis management operation launched by the government during the incident involving the British Trent tanker; in 1995 following the collision between the ‘Carina’ and the ‘Samia’; in 2001 when the ‘Heinrich Behrman’ ran aground; in 2002-2003 for the ‘Tricolor’ and ‘Vicky’ incidents; more recently, in 2012 during the passage of the severely damaged container ship the ‘Flaminia’; the sinking of the car carrier ‘Baltic Ace’ in 2014-15; and the incident of the sinking of the ‘Flinterstar’ off Zeebrugge in 2015-16. In the ‘Tricolor’ and ‘Flinterstar’ incidents alone more than 50 oil pollution cases at sea were observed and reported to the authorities during the incident period as a whole, and the aircraft was deployed for several weeks to guide the pollution fighting vessels.

everdecent incident
tricolor incident


Westhinder incident (1992) Gudermes/St.Jacques II (2001)
Cast Muskox/Long Lin (1992) Heinrich Behrmann (2001)
Amer Fuji/Meritas (1992) Tricolor/Kariba (2002-04) (+ salvage of Tricolor)
Davidgas/Athos (1992) Vicky (2003)
Aya/Wladyslaw Jagiello (1993) Pauline (2007)
British Trent/Western Winner (1993) Sapphire (2007)
Carina/Samia (1995) High Progress/Advent (2009)
Spauwer (1995) Z700-Rapke (2011)
Mundial Car/Jane (1997) Flaminia (2012)
Adelaide/Saar Ore (2000) Baltic Ace/Corvus J (2012-15) (+ salvage of Baltic Ace)
Vera/Music (2001) Flinterstar/Al Oraicq (2015-16) (+ salvage of Flinterstar)
Shipping accidents in and around Belgian marine areas with (a major risk of) accidental sea pollution by oil and/or other noxious liquid substances in which the aircraft was used to monitor and/or provide air support (1991-present).