Rivers – Approaches for evaluation of anthropic alteration

INHABIT project

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Home Themes & Results Innovative measures (I3) Evaluation of anthropic alterations

Rivers – Approaches for evaluation of anthropic alteration

Human impact on river environment may occur on different spatial scales: it could appear as an immediate and local impact, confined to the area directly in contact with or close to the primary source of alteration, or it could have consequences visible and measurable on major scales, involving processes that develop spatially and temporally over longer intervals. The first case does include alterations regarding erosion/deposit forms or bank areas, associated to a pressure. In the second case, we mostly refer to alterations regarding morphological processes and river dynamics, with possible effects on the equilibrium profile of the river or on changes in the shapes of the channel pattern (that can change, for example, from one morphological type to another).

The studies carried out within INHABIT project I3 group of actions, have thoroughly illustrated the potential of CARAVAGGIO method in detecting alterations specifically affecting habitats and related biotic communities. The method is designed and structured to provide snapshots of river environments on the surveyed area, allowing to depict in detail characteristics and possible impairments of in-channel and riparian habitats. On the other hand, it cannot properly record alterations related to variations in the river dynamics set on a larger scale, for alterations of this magnitude are not necessarily perceived locally (for instance, a change in the channel shape will be accompanied by a change in local habitats and communities, in balance with it). Other methods, such as the MQI (Morphological Quality Index) or procedures of geographic modeling, allow the assessment of river system complexity and changes in its balance and they will apply to water body and river basin spatial scale. On the other side, such tools cannot describe and grasp in detail the fragmented river mosaic and its components.

Within INHABIT project I3 group of actions, in particular among the activities described in Deliverable I3d2, we proceeded in a comparison between the results obtained from surveys undertaken with both CARAVAGGIO and MQI (or geographic modeling) methods on the same river water bodies/reaches investigated in INHABIT (considering both recorded data and processed information), in order to verify possible harmonization or integration among the different assessment approaches. The comparison has highlighted similarities and differences in the two methods for what the approaches and the resulting descriptors is concerned, confirming the general correspondence regarding the assessment of impacts on medium spatial scale (reach) and the different responses to the variations estimated over wider spatial elements or related to decennial temporal scales (e.g.  the previously mentioned change in cannel pattern). However it is important to emphasize that, even in the matching outcomes, the two methods express evaluations enhanced by their characterizing elements, according to the different purposes for which they were developed.

On the basis of the needed priorities to be assessed, and depending on the aims of the study - if quantifying the direct and locally significant alterations that can affect river habitats and biotic communities, or if quantifying the long-term impacts that may affect river processes on a large-scale - different evaluation methods should be applied. Such methods are not mutually exclusive but they complement and complete each other, recreating a layered system of information that can be used to different levels of application.

A thorough description of the CARAVAGGIO method is available in the Manual of the method (in Italian), that the activities of the project INHABIT allowed to finalize. The manual is distributed as an attachment to the Deliverable I3d2 and will soon be available for free download on this website (Manuale CARAVAGGIO)