Hydraulic landscapes and irrigation systemsSome distance from the levees occur flood basins o f clay-rich and usually saline soils
that accumulate floodwaters from the rivers or the overflow from canals (Figure 2.2).
In the long term, such depressions became marshes that together with the perennial
and estuarine marshes characteristic o f the head o f the G u lf contributed to the overall
verdant nature o f the lower plains. In the vicinity o f the estuaries, the slight rise and fall
o f the tides also provided a natural system o f irrigation as well as drainage which allows
soils to be leached thereby mitigating the more extreme forms o f salinisation.
In addition to providing the foundation for local irrigation networks, the raised
anastomosing channels provided the framework for the distinctive alignments o f third
m illennium settlements discussed by Jacobsen, Adams and Nissen (see U r this
volume). Nevertheless, as argued by Pournelle (2007), the earlier patterns o f settlement
appear to have been less linear than those o f the Early Dynastic and later periods
because during the U baid the mosaic o f ‘turtlebacks’ and wetlands were also an
important locus o f settlement.
Unfortunately, this verdant ‘Garden o f Eden was marred by the tendency o f
the rivers to occasionally burst their banks and adopt new channels, a process
known as avulsion. Such catastrophic events, w hich are a well-known feature o f the
M esopotam ian plains (Gibson 1973; Adams 1981; W ilkinson, T.J. 2003: 84-85;
M orozova 2005), could lead to entire settlement systems being left without water, but
equally could have created new channels and new opportunities for settlement. This
Figure 2.2
Levees and flood basins in the
southern alluvium around
modern Suq al-Shuyukh
(re-drafted from Buringh i960:
fig- 97)0 5 km
N