often merged by the disposal of materials, dredged in the navigation channel, in a
non-navigated arm.
These island modifications had multiple consequences: the relatively still waters,
used as resting areas, refuges during floods, spawning grounds and/or fishing
grounds for some fish species have decreased. The total length of river banks per
kilometre of river course has also markedly decreased (around 30% between the
1880s and 2010) as well as river habitat heterogeneity.
5 Conclusion and Perspectives
In Western European rivers, physical changes have affected the lower and medium
stream orders since the Middle Ages, and sometimes earlier, as demonstrated by
archeo-geology [3]. The heritage of these slow and gradual changes, and the related
cultural elements (mills, ponds, etc.), has been represented with accuracy and
precision since the early 1800s in various cartographic documents.
The selected cartographic documents mainly represent the visions that engineers
had on these areas at each period, particularly on the fluvial area. But they can also be
used to reconstruct, within our contemporary knowledge and technical means, the
longue durée evolution of the river and stream network, the river channel in its three
dimensions – longitudinal, lateral and vertical – and its related floodplain and the
river-related natural and cultural elements represented. Our contemporary interpretations of these documents must be cautious: the reliability of these ancient documents must be assessed. The context and the objective of the cartographic work must
be established, with its quality, accuracy, imprecision and relevance with regard to
the contemporary research objectives [62].
These well-contextualised cartographic documents were used to perform quantified geo-historical analyses through two main approaches: (1) the analysis of the
state of the river at a given period and (2) the comparison of two states, which
provides the dynamics of the elements represented.
The applications of the analysis of historical cartographic documents are
numerous: they can be used to investigate hydro-morphology, hydro-ecology,
water resources and river use history, as well as river restoration and management.
These natural and/or human-made changes lead to new hydraulic and hydrodynamic
conditions which eventually reshape the river course and the aquatic environment, as
evidenced by the evolution of the morphometric parameters. In turn the aquatic biota
readapts to these new conditions. In the case of river works, the most frequent one,
the related adjustments provide the response times of the aquatic environment to the
pressures exerted on them. As these responses are often on the decadal or multidecadal scale, analysis of cartographic archives is essential.
The physical modifications documented here have been found for every stream
order, from the headwaters (e.g. Versailles plateau, Morvan forest) to the riverestuary limit (Poses sector, order 7). Several drivers are responsible for these
52
L. Lestel et al.
non-navigated arm.
These island modifications had multiple consequences: the relatively still waters,
used as resting areas, refuges during floods, spawning grounds and/or fishing
grounds for some fish species have decreased. The total length of river banks per
kilometre of river course has also markedly decreased (around 30% between the
1880s and 2010) as well as river habitat heterogeneity.
5 Conclusion and Perspectives
In Western European rivers, physical changes have affected the lower and medium
stream orders since the Middle Ages, and sometimes earlier, as demonstrated by
archeo-geology [3]. The heritage of these slow and gradual changes, and the related
cultural elements (mills, ponds, etc.), has been represented with accuracy and
precision since the early 1800s in various cartographic documents.
The selected cartographic documents mainly represent the visions that engineers
had on these areas at each period, particularly on the fluvial area. But they can also be
used to reconstruct, within our contemporary knowledge and technical means, the
longue durée evolution of the river and stream network, the river channel in its three
dimensions – longitudinal, lateral and vertical – and its related floodplain and the
river-related natural and cultural elements represented. Our contemporary interpretations of these documents must be cautious: the reliability of these ancient documents must be assessed. The context and the objective of the cartographic work must
be established, with its quality, accuracy, imprecision and relevance with regard to
the contemporary research objectives [62].
These well-contextualised cartographic documents were used to perform quantified geo-historical analyses through two main approaches: (1) the analysis of the
state of the river at a given period and (2) the comparison of two states, which
provides the dynamics of the elements represented.
The applications of the analysis of historical cartographic documents are
numerous: they can be used to investigate hydro-morphology, hydro-ecology,
water resources and river use history, as well as river restoration and management.
These natural and/or human-made changes lead to new hydraulic and hydrodynamic
conditions which eventually reshape the river course and the aquatic environment, as
evidenced by the evolution of the morphometric parameters. In turn the aquatic biota
readapts to these new conditions. In the case of river works, the most frequent one,
the related adjustments provide the response times of the aquatic environment to the
pressures exerted on them. As these responses are often on the decadal or multidecadal scale, analysis of cartographic archives is essential.
The physical modifications documented here have been found for every stream
order, from the headwaters (e.g. Versailles plateau, Morvan forest) to the riverestuary limit (Poses sector, order 7). Several drivers are responsible for these
52
L. Lestel et al.