In the 18th century, shipping on the Merwede was regularly troubled by sandbanks and shallows. For example, some sandbars formed near Hardinxveld in the long run, which were a nuisance for ships, especially at low tide. Shallow areas also existed near the harbour of Werkendam, which continued to grow despite all kinds of countermeasures.
This map made by the surveyor Melchior Bolstra (1704-1776) shows the Merwede between Papendrecht and Dordrecht in 1761. On this stretch, too, siltation had to be dealt with, which made it difficult for the city of Dordrecht to reach the shipping traffic. Together with the Inspector General Johan Lulofs (1754-1768), Bolstra had twelve river soundings made and marked on the map. These soundings were compared to earlier soundings made in the period 1738-1741 for the survey map of the Merwede. These showed that the river had widened on the northern side, while the southern part was gradually silting up. It also showed that the Noord, the connection between the Merwede and the Nieuwe Maas, was suffering from considerable sedimentation.
The map is appended to the States Resolution of 3 April 1761 regarding a river engineering report written by Lulofs, 'Rapport van eenige inspectien en peilingen van de Merwede, zo bij Dordrecht, als bij Hardinxveld, Leiden, 25 November 1760'.
