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Box 3.1           German floodplain inventory and assessment

A first nationwide consistent and updatable inventory of the loss and quality status of German floodplains provides an efficient overview of the position, dimension and status of floodplains at larger rivers in Germany (Brunotte, et al., 2009). The survey of the floodplain areas was conducted for sections of the rivers with a catchment area of at least 1 000 km² and tidal waters were not included. The geomorphologic floodplain, consisting of the remaining active and former floodplains, which is defined in this case as the area which could be inundated, if there were no man-made dikes was assessed. For each 1-km section of the rivers, separately for the left and the right side, the active and former floodplain areas were mapped and land use cover in seven classes, nature conservation value, and protection status were documented

Based on a standardized approach (Koenzen, 2005) to define reference conditions for riverine landscapes (their potential natural status), the status of all mapped floodplains was assessed. Main input data for this assesment comprises the main factors of habitat quality for all species, including the geomorphologic and hydrologic habitat conditions, and land use.

As for the Water Framework Directive (EU 2000) the floodplain assessment methodology refers to a reference status (which is close to being unaffected by human intervention) and the results are  presented in five classes giving the degree of modification compared to the potentially natural status (table 3.2).

Floodplains of larger rivers in the past covered about 15 000 km², which corresponds to 4.4% of the German territory. Two-thirds of the morphological floodplain was lost by embanking. At large parts of rivers like Rhine, Elbe, Danube and Oder only 10-20 % of the former floodplains can still be inundated nowadays. More than one-third of the remaining active floodplains are intensively used as arable land use (28 %) or urban (6 %) areas and less than 10 % of the active floodplains fully provide their ecological functions. The remaining near-natural hardwood forests of floodplains cover only about 1 % of the active floodplain area. Compared to the potential natural status, less than 1% of the assessed active floodplain sections are classified as “nearly natural” (see figure 3.1), while 54 % of the floodplain sections are assessed as “severely modified” or “totally modified”. On the one hand, this situation resulted from the intense agricultural use on fertile soils of floodplains and on the other hand from the former importance of rivers as waterways for transport and trade as well as the arising urbanisation.

As expected, the classes severely modified and totally modified are more abundant (79 %) in the former floodplains compared to active floodplains (54%). However, there is a small percentage (4 %) of “slightly modified” former floodplain sections, which apparently still maintained a “floodplain- like” environment without being inundated for a longer period. Hence, these areas should be targeted for a potential restoration (activation) of former floodplains.

Source: (BMU et al., 2009), see http://www.geodienste.bfn.de/flussauen online