The map presented here serves as a context and index sheet for the detailed two-sheet map of the Merwede between Woudrichem and Hardinxveld of 1730 by Nicolaas Cruquius. The survey map was also made by Cruquius and concerns the hydrographical difficulties around the Merwede at that time. For a long time, the river formed one of the biggest problem areas in the Dutch river system. Especially after the Sint-Elisabethflood of 1421 - when the Biesbosch was given the opportunity to develop gradually - the hydraulic situation became precarious. Along the undyked southern bank of the Merwede was the northern boundary of the extensive Biesbosch. This area consisted of many watercourses, so-called kills, which carried most of the Merwede water to the North Sea via the Hollands Diep. However, the Merwede itself had less water to swallow, which made it increasingly difficult to keep the river at the required depth.
For the harbour cities of Dordrecht, Rotterdam, Delft, Schiedam and Brielle, good navigability of the Merwede and, downstream, of the Lower Maas was of economic importance. These cities did everything in their power to guarantee shipping on both rivers by fully or partially closing off the Biesbosch. However, the problem was that the city of Gorinchem and the water boards upstream had great difficulty with a closure of the Biesbosch. After all, they benefited from a safe discharge of water and ice through an open Biesbosch. Closing off this drainage area without simultaneously reinforcing the northern river bank was unacceptable to them.
This 18th century contrast between the five Maassteden and Gorinchem forms the backdrop of this map of the Merwede between Gorinchem and Dordrecht, made by Nicolaas Cruquius (1678-1754) in 1729-1730. At that time, there was a continuous discussion about the way in which the improvement of the water conditions of the Merwede should be tackled. Between 1726 and 1746 the States of Holland made three frantic attempts to find a solution, each time accompanied by river engineering reports and accompanying maps. Cruquius' map was made for the second attempt at mediation, in the period 1729-1734.
In February 1729, as in 1726, high water levels and ice masses were once again a problem. A large ice dam had formed near Giessendam, closing the Merwede and thus blocking it. Because of a breach in the Waal dike, the Tielerwaard was under water and the water accumulated in front of the Lingedijk. For a moment, people feared a repetition of the events of 1726, when this dike broke. Fortunately, there was movement in the ice dam at Giessendam, which allowed large amounts of water and loose ice floes to be discharged through the channels of the Biesbosch. Several dams that had been erected here in 1727 and 1728 fell prey to the water and ice currents. However, the water level in the Merwede rapidly dropped and thus the danger of dike breaches and floods had temporarily disappeared.
The city of Gorinchem thought that the events of 1729 showed that the Biesbosch channels should not be closed without also constructing a spillway through the Land van Altena. Because the States of Holland were not convinced, they decided to submit Gorinchem's proposal to three neutral experts, among them the surveyor Nicolaas Cruquius. They had to draw up an improvement plan in a short period of time, but it would take a year before this would be written down. The report showed, among other things, that the Merwede had a very irregular depth. In addition, there were large differences in flow velocity. It turned out that no less than two thirds of the water mass of the Merwede drained via the Biesbosch. Partly due to this and to sedimentation, the Merwede threatened to become unnavigable for shipping.
The improvement plan was based in the first place on removing obstacles in the river's winter bed. Secondly, the plan provided for the construction of a spillway through the Land of Altena or via the north bank of the Merwede. On completion of this spillway, the Oude Wiel, the large channel to the Biesbosch, was to be dammed up, with an opening for shipping towards the local villages.
Cruquius' river map was an integral part of the recovery plan. In fact, it consisted of the two-page detailed map mentioned earlier and the survey map shown here. Cruquius based this survey map on existing map material. The sources included an accurate handwritten map of the Grote West Kil by surveyors Mattheus van Nispen, Abel de Vries and Mattheus de Vries.
The overview map shows the entire Merwede river basin and places the river's water problems in a broader spatial context. Two rectangles in the upper right corner show the area covered by the two-sheet main map and thus form a bookmark. The measures to be taken from the recovery plan are well highlighted on the survey map. A dam (letter 'F') is marked at the upper mouth of the Oude Wiel, with an opening for shipping. The spillway areas through the Land of Altena and via the northern bank of the Merwede are also shaded in grey. Also indicated are the hydraulic provisions and measures for these projected spillways, such as the construction of new dikes and dike heightening or lowering.
At the bottom Cruquius' map has numerous cross-sections and diagrams of tides. With these diagrams he introduced a statistical novelty. They include, for instance, six cross-sections of the riverbed near the Oude Wiel. On the main and overview map these profiles are shown with a railing line and letter. The profiles show the great variation in the width and depth of the Merwede at the location. Factors such as water run-off via the Biesbosch, tidal effects and barriers in the river bed had a major influence on flow velocity. Cruquius took measurements of these at Hardinxveld and incorporated them in the graph in the centre left. Next to it is a longitudinal profile of the Merwede with the height of the dike between Papendrecht and Dalem. Finally, the bottom diagram shows the high and low water levels between June 1729 and March 1730, as observed at Hardinxveld.
The final report with the accompanying maps was presented to the States of Holland in July 1730. However, due to disputes between Gorinchem and the five Maas cities, a difficult compromise was only reached in September 1730. This meant that no spillway was built and also that the Oude Wiel was not dammed up. What remained of the recovery plan was merely the clearing of the riverbed, which was done only to a limited extent.
The printed map by Cruquius was an annex to the resolution of 12 July 1730 concerning the 'Report of professors 's-Gravesande and Wittichius, and of the surveyor Cruquius, on their inspection of the river Merwede from Gorinchem downstream, and on the means employed to prevent inundation'.
