Lessons Learned
After three years of dredging the river discharge had increased and the river was flowing all year round, thus increasing its navigability. The year-round supply of water to the delta led to a reduction of the salinity intrusion into river and the surrounding areas. Consequently, the fish population increased. However, maintenance dredging turned out to be crucial, as the river starts silting up as soon as dredging is stopped.
Because of uncertainty it made little sense to set dredging volumes and locations on beforehand. In an uncertain environment like this more flexible measures are needed. Also, the time between design-survey and approval of dredging proposals needs shortening, as the river morphology changes fast. Close monitoring and associated modelling has led to new insights into the behavior of the river. This examples shows that the approach promoted by Building with Nature and applied here can give a technically sustainable solution. Due to governance complications, however, this particular project could not be shown to be sustainable in the long run.