taming and dedication of the river to human uses. These changes were made in
several steps, corresponding to political decisions and technical innovations
[33]. River reaches were mapped in three dimensions with great precision and
accuracy prior to any construction works, leaving behind precious archives that
are used today to access the initial river course morphology.
Until the 1940s, the river level within Paris was not regulated, and extreme low
levels were observed in summer (Fig. 1k). In 1910, an exceptional event occurred:
the flooding of Paris and its suburbs by a 100-year return period flood. Another
phase of river management ensued. The new objective was to maintain the river level
at a fixed value Æ35 cm, with minimum river discharge variations [34]. Flood
protection and low-water discharge regulation for Paris led to the creation of four
main reservoirs, which were constructed in the 1930s–1980s on the Yonne, Upper
Seine, Aube and Marne rivers (schematically represented in Fig. 1), some 250 river
km upstream of Paris. These facilities, financed by the city of Paris, increased the
summer low flows from 25 m
3 /s (extreme value at Paris) up to 100 m
3 /s, thus
reducing the impact of the Paris region on the water quality of the Lower Seine.
When comparing the 1800 and 2000 figures, the weight of Paris on the Seine
River course is enormous, considering the local and proximal changes such as the
artificialisation of the river courses within Paris, the high regulation of discharge and
the water level, the loss of many suburban river reaches or the modification of the
water balance over the urbanised sectors. But Paris also controls the river in a
distal mode, either upstream by the regulation reservoirs for flood protection and
low-water enhancement or 100–250 km around Paris on regulated and navigated
river reaches and by the sandpit excavation. Many of these river transformations can
be documented with historical maps. Cartographic document analysis can also be
complemented by other approaches to assess the slow longue durée evolution of the
river, such as the use of former furnace slags to measure the very slow river bedload
movement (Box 1).
Box 1 Historical Slag Residues: Another Approach to Slow River
Dynamics
In lowland meandering rivers such as the Seine, riverbed transport is very slow
and the deposited sand-gravel material might only move during medium rare
to rare events. In these rivers with relatively low energy and therefore with low
morpho-sedimentary adjustments, the impact of obstacles such as weirs, river
mill diversions, small reservoirs and navigation sluices is relatively unknown.
Coarse sediment transport in the Seine basin occurs at a slow pace, which
can be quantified by the analysis of slag residues from historical high-furnace
iron smelting, even if mill weirs have temporarily or permanently interrupted
or disturbed sedimentary transit for several centuries.
(continued)
The Evolution of the Seine Basin Water Bodies Through Historical Maps
35
several steps, corresponding to political decisions and technical innovations
[33]. River reaches were mapped in three dimensions with great precision and
accuracy prior to any construction works, leaving behind precious archives that
are used today to access the initial river course morphology.
Until the 1940s, the river level within Paris was not regulated, and extreme low
levels were observed in summer (Fig. 1k). In 1910, an exceptional event occurred:
the flooding of Paris and its suburbs by a 100-year return period flood. Another
phase of river management ensued. The new objective was to maintain the river level
at a fixed value Æ35 cm, with minimum river discharge variations [34]. Flood
protection and low-water discharge regulation for Paris led to the creation of four
main reservoirs, which were constructed in the 1930s–1980s on the Yonne, Upper
Seine, Aube and Marne rivers (schematically represented in Fig. 1), some 250 river
km upstream of Paris. These facilities, financed by the city of Paris, increased the
summer low flows from 25 m
3 /s (extreme value at Paris) up to 100 m
3 /s, thus
reducing the impact of the Paris region on the water quality of the Lower Seine.
When comparing the 1800 and 2000 figures, the weight of Paris on the Seine
River course is enormous, considering the local and proximal changes such as the
artificialisation of the river courses within Paris, the high regulation of discharge and
the water level, the loss of many suburban river reaches or the modification of the
water balance over the urbanised sectors. But Paris also controls the river in a
distal mode, either upstream by the regulation reservoirs for flood protection and
low-water enhancement or 100–250 km around Paris on regulated and navigated
river reaches and by the sandpit excavation. Many of these river transformations can
be documented with historical maps. Cartographic document analysis can also be
complemented by other approaches to assess the slow longue durée evolution of the
river, such as the use of former furnace slags to measure the very slow river bedload
movement (Box 1).
Box 1 Historical Slag Residues: Another Approach to Slow River
Dynamics
In lowland meandering rivers such as the Seine, riverbed transport is very slow
and the deposited sand-gravel material might only move during medium rare
to rare events. In these rivers with relatively low energy and therefore with low
morpho-sedimentary adjustments, the impact of obstacles such as weirs, river
mill diversions, small reservoirs and navigation sluices is relatively unknown.
Coarse sediment transport in the Seine basin occurs at a slow pace, which
can be quantified by the analysis of slag residues from historical high-furnace
iron smelting, even if mill weirs have temporarily or permanently interrupted
or disturbed sedimentary transit for several centuries.
(continued)
The Evolution of the Seine Basin Water Bodies Through Historical Maps
35