Rivers – Approaches for possible hydromorphological features upscaling

INHABIT project

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Rivers – Approaches for possible hydromorphological features upscaling

The River Basin Management Plans (RBMPs) are the administrative tool for achieving WFD objectives. Within RBMPs a list of necessary measures and possible restoration actions is included on the basis of pressures and assessment of hydro-morphological conditions of water bodies. RBMPs are necessarily set to water body / catchment spatial scale, both for assessments acquisition and measures definition. However, morphological and hydrological characteristics related to water and riparian habitats represent the interface between the biotic communities, whose quality expresses the ecosystem quality – primary objective of the directive –,  and the river system. For this reason, in rivers, the knowledge of the hydro-morphological conditions at the local scale provides the most suitable tool to understand changes related to the quality of biotic communities and to verify related measures. It is therefore necessary to set up an information transfer mode from a spatial scale to another, that would allow to optimize resources, and, above all, to create a path of integrated analysis of the procedures; such analysis could then be used by water managers to implement measures for the benefit of the river system as a whole, river ecosystems and related biological communities.

Within INHABIT project I3 group of actions, and in particular among the activities described in Deliverable I3d2, we approached the problem of data and information transfer between different scales, mainly through the application of spatial analysis models that could make full use of the detailed local-scale collected hydro-morphological data from CARAVAGGIO method to verify and validate the assessments carried out on large scale, at watershed level. This activity was carried out by correlating modeled information with comparable information collected in the field by CARAVAGGIO method; in particular riparian vegetation data and bank erosion data were considered.

In contrast, the comparison between the assessment methods performed on a large scale and CARAVAGGIO has allowed us to verify, as first instance, the potential for direct information transfer from CARAVAGGIO to larger scales (up-scaling). Beyond the elements that cannot be fully recorded, due to the limited scale of observation in terms of both time and space, or elements that are not recorded because they are not considered by the method, the real limits of a possible up-scaling lay in the positioning of the CARAVAGGIO stretches, when it is not realistically possible to collect data from the entire river. The representativeness of the stretch, or stretches, which must represent prevalent morphological conditions and sources of alteration, becomes the key to the reliability of the up-scaling procedure. If the river stretch was chosen for purposes other than representativeness, most significant discrepancies can emerge and an up-scaling process could be misleading. The same criteria that make the method efficient, i.e. the ability to record a large amount of detailed and real information, can also necessarily represent its limit, in case of the surveyed stretch being characterized by particular features and/or local non-homogeneities which, although interesting, could describe only a peculiar portion of the river system. The anomalies recorded at a local scale, when up-scaled, must necessarily weigh in proportion to the larger scale. On the other hand, these circumstances, especially if related to positive features, may represent specific hydromorphological and habitat conditions that is worth considering in the management of that water body, just by virtue of their uniqueness (e.g. a portion of the river that has a good diversification of habitats in an overall degraded context). It follows that up-scaling process should not provide loss of information, but it should rather aim at its improvement, in addition to the validation of analysis on a large scale.