Wetland drainage and flood mitigation works have had a profound influence on hydrology, especially hydroperiod and tidal exchange across coastal NSW.

Barriers or instream artificial tidal impediments that may limit blue carbon opportunities were selected from the NSW Government Fish Passage Dataset. This dataset indicates the location of in stream structures or barriers that may influence tidal exchange across NSW. This dataset was provided by the Department of Primary Industries: Fisheries. Some manipulation of data was necessary due to geospatial errors in the position of some tidal barriers. A 1 km buffer was identified at each tidal limit, and barriers within this buffer were considered to serve as a tidal impediment. Expert opinion from NSW Government Department of Primary Industries Fisheries officers verified the position of tidal barriers and their effectiveness as a tidal impediment.