Use constraints: Data can be used freely given that the source is cited (following creative commons license CC-BY). The source should be cited as: “HELCOM HOLAS II Dataset: Dredging areas 2011-2016 (2018)”.

Data processing:

For Estonia, dataset submitted was in WGS84 and transformed to ETRS 1989 LAEA. Dataset includes the permitted dredging site with location and description of dredging site, permitted dredging and deposit of solid material, and year of activity.

For Latvia, dataset submitted includes the X and Y coordinates of dredging sites, corresponding area (km2), amount of dredged material (tons), type of activity, and year of activity.

For Finland, 6 datasets were received in total. The data were cleaned and only dredging activity done during 2011 to 2016 were selected. Some of the information do not have corresponding spatial data but those with spatial data was reported in EUREF-FIN and was transformed to ETRS 1989 LAEA. An updated dataset was received from Finland for the 2018 version.

For Lithuania, two data sets for the year 2012 and 2013 were received from the Environmental Protection Agency. Dredging in year 2014 was reported through HELCOM Recommendation 36-2. The spatial data was reported in WGS 84 and transformed to ETRS 1989 LAEA.

For Germany, the dataset has been collected from regional planning authorities and merged as a national dataset. Some of the information do not have spatial data but those with spatial data was reported in WGS 84 and transformed to ETRS 1989 LAEA. The submitted dataset includes some X and Y coordinates, area (km2), and year of activity only.

For Poland, the dataset has been collected from Maritime Office in Gdynia, Slupsk and Szczecin and merged as a national dataset. The dataset is not complete as some dredging locations were not reported as spatial data.

Data coverage:

Russian data was extracted from reporting for HELCOM Recommendation 36-2, other countries' data is based on response to national data call.

For Sweden, The data has been collected from court decisions and additional information from county administrative boards.

• In the list, dredging sometimes appears twice from the same year and place. It is due to the fact that one row in the list represents the material disposed at sea and the other row in the list represents the material disposed at land. However, that is not always the case, sometimes the material disposed at sea and land is added in the same row.

• It is important to note that the area of the dredging activity is unique for that dredging code. However, in reality it may be that one part of the area was dredged one year and one part was dredged another year. This is especially true for capital dredging.

• The polygons were digitized from paper copies of maps. The polygons are simplified due to time limits for this project. The area included in polygons can therefore in many cases be overestimated compared to the area actually dredged. Five different methods where therefore used for estimating the area, see the Table below. The ranking of methods in the table also reflects their uncertainty, method 4 and 5 are especially uncertain. An updated dataset was received from Sweden for the 2018 version, including small scale dredging sites.

The reported area is based on the following 5 methods (as referred to in the data sheet):

1. a court decision or underlying information to that decision.

2. calculations and assumption based on a court decision or underlying information to that decision.

3. is likely a dredging that only requires a “notification”. Therefore the area is assumed to be 3000 m2 since that is the maximal area for that type of dredging.

4. the area of the polygon, only a few cases.

5. the volume. We have assumed a dredging depth of 2 meters. This value is very uncertain

Data source:

National data provider

Estonia: Ministry of the Environment

Finland: Finnish Environment Institute

Latvia: State Environmental Service of Latvia

Lithuania: Environmental Protection Agency

Germany: Federal Institute of Hydrology

Poland: Maritime Office in Gdynia, Slupsk and Szczecin

Russia: SPb PO “ Ecology&business”

Sweden: Swedish Agency for Marine and Water Management

Attribute information:

Country: Country

National ID: National reporting id

HELCOM site ID: HELCOM site ID for dredging site

Site name: Dredging site name

Dredging type: Type of dredging activity

Year: Year of dredging activity

Amount 2011-2016: Amount per year (if site used on several years)

Total 2011-2016: Total amount of dredged material for all years

The data set was approved by all HELCOM Contracting Parties in the HOLAS II Human activities data review process during first quarter of 2018.