The Dutch Rhine and Meuse rivers are such examples and are strictly
managed to ensure that the hydraulic roughness in the embanked
floodplains will not increase water levels during a flooding . The Dutch
floodplains consist roughly of 30% intense agricultural use, 26%
natural grassland, 23% open water, 5% bare or built, 6% forest &
bush . Vegetation management consists of small-scale management such as
mowing, grazing or harvesting of woody vegetation. Natural parts of the
floodplains are often extensively grazed by cattle and wild horses to
slow ecological succession, while agricultural areas are managed more
intensively through harvesting and mowing. Quickly developing pioneer
floodplain forests characterized by fast growing willows or maythorn
shrubs will often be removed by tree felling in specific plots of this
types of vegetation.
There are approximately 12.000 landowners in these floodplain areas,
ranging from farmers (both crops and cattle grazing) to NGOs and private
entities owning property in the floodplains. The challenge for the
National Water Authority ‘Rijkswaterstaat’ is to focus efforts in the
management of this vegetation in good dialogue with all these different
owners, as they are responsible for timely management of vegetation on
the land they own in line with legal requirements.
Present day monitoring of the floodplain vegetation is done via aerial
photointerpretation and these maps are generated once per six years.
These maps are translated into hydraulic roughness classes and used as
input to the official hydraulic models for water level calculations to
check on flood safety standards . The manual once per six-year update of
the ecotope maps is costly and time consuming. There is a need for cost
efficient up-to-date monitoring of vegetation. Remote sensing is a
proven technology for large scale monitoring and has been tested in the
past on Dutch floodplains but had not moved to an operational platform