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: “Organisation: Name of dataset (Year)”.

For Poland “HELCOM HOLAS II Dataset: Coastal defence”.

The Danish national dataset was originally established in 1998-1999 based on aerial photos and has been constantly updated. The construction is brought into the dataset after they have been issued a license to construct. Updates are done quarterly (4 times in a year). The accuracy is 1-20 meters depending on whether the construction itself or the area of construction is recorded. The Danish dataset contains the following types of constructions: New construction, breakwater, jetty (updated untill 1998), structure, dike, mixed structure, groyne, slope protection, T groyne, outer groyne, stones, artificial reef (updated untill 1998), emission (updated untill 1998), sand nourishment and bypass.

From Estonia the dataset has been collected from the permits for the special use of water available via Republic of Estonia Environmental Board environmental services webpage: ( https://eteenus.keskkonnaamet.ee/

?page=avalik_stat_koond&act=avalik_info&u=20160316143654) and via Building Register webpage ( https://www.ehr.ee/app/esileht?0).

Data regarding length and area of coastal defence systems is given if available from the special use of water or from building permits. For some structures it is not known, whether they are already constructed, thus estimated time of completion (same as the end date on the permit) is given. For some structure the construction year is not known and this is marked as no data (ND).

Original point data from Finland was transformed into uniform data type by creating a 10 m line from each point. The original point was set to be the line midpoint. The original XY coordinates can be found from the attributes (X_lon and Y_lat). Activities on the inland was removed from the dataset.

Area (km2) of coastal defence structures was given for some and calculated for those structures that had information on both length and width. Often all attribute information has not been reported or logged into the database and can therefore be lacking.

For Germany, data only for the activities on the coast of Mecklenburg-Vorpommern are shown in the dataset. On the coast of Schleswig-Holstein, there are only minor activities of third parties which are not INSPIRE-relevant, not part of the public coastal defense plan, and for which data is not accessible. The coastal defense data relate to new defense measures in the period 2011-2016. For Mecklenburg-Vorpommern the data set includes:

- beach nourishment, reconstruction

- groyne, reconstruction

- sea wall, new building

The data from Poland is a compilation of data delivered by Maritime Offices in Gdynia, Slupsk and Szczecin.

Swedish data set is based on information in court decisions, the Swedish maritime administration and two different map providers: Lantmäteriet and Google Earth. Court decisions are used to identify places where constructions have occurred. There is a bias towards places where dredging has occurred, since this type of information has been characterised for the years 2011-2016 in another Holas2 data-set. This identification processes has been complemented with notification from the Swedish maritime administration and searching in the Swedish Agency for Marine and Water Management archives for cases related to coastal defence. However, these archives do not generally contain decisions on erosion protections. There are likely many more places where coastal defence have been constructed in Sweden during this time period. Especially coastal protection like seawalls and riprap are very common along the Swedish coastal line. However, these types of decisions are hard to identify. Beach replenishment is rather uncommon in Sweden, compared to for example Denmark, but will likely be used more in the coming year due to erosion in south of Sweden. The area for coastal defence has not been estimated for this data set since this type of information is missing in the decisions. The length of the modified coastline is simply the length of the constructions. However, a construction or beach replenishment could affect a much larger part of the coastline, depending on for example streams, pollutants, etc. The quality of this data set is rather low since it is difficult to determine from maps and court decisions if coastal defence has been constructed or not

The dataset was approved by all HELCOM Contracting Parties in the HOLAS II Human activities data review process during first quarter of 2017.

National data provider

Denmark: The Danish Coastal Authority (Kystdirektoratet)

Estonia: Republic of Estonia Environmental Board, Building Register

Finland: Finnish Environment Institute (Freshwater Centre)

Germany: State Agency of Agriculture and Environment Mittleres Mecklenburg

Poland: Ministry of Maritime Economy and Inland Navigation

Sweden: Swedish maritime administration, Lantmäteriet and Google Earth

Data quality: Dataset is unbalanced between countries, as a result of national interpretation of the definition of a coastal defence structure. More precise data is available from Denmark compared to other countries.

Data coverage: Whole Baltic Sea, excluding Latvia and Russia

Temporal coverage: Temporal coverage varies, as some countries have reported data for 2011-2016 and some countries have included more historical data.