Avulsions and Ancient Settlement Patterns in Lower Mesopotamia Galina S. Morozova

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Avulsions and Ancient Settlement Patterns in
Lower MesopotamiaGalina S. Morozova
http//joseph_berrigan.tripod.com/ancientbabylon/i
d14.html
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http//joseph_berrigan.tripod.com/ancientbabylon/i
d1.html
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(Adams, 1981 Sanlaville, 1989 Cole Gasche,
1998 Uchupi et al., 1999)
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Distribution of settlements by size during
different periods of Mesopotamian history (based
on Adams, 1981)
200.1ha
10.1-20 ha
20.1-40 ha
4.1-10 ha
40.1-200 ha
of settlements
Onset of settlement
0.1-4 ha
Ubaid
Islamic
Cassite
Akkadian
Sasanian
Late Uruk
Jemder Nasr
Post Cassite
Old Babylonian
Isin-Larsa/UR III
Early Dynastic I-III
Parthian/Seleucid
Early- Middle Uruk
Early Neo-Babylonian
Neo-Bab/Achaemenid
periods
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A
A
Cross section along AA
A
new channel belt

A
avulsion point
avulsed channel belt
Avulsion is a major river diversion to a lower
elevation on the floodplain in which the older
channel becomes abandoned and a new channel is
initiated
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Samarra
Tigris
Euphrates
Dayr
Baghdad
Fallujah
Sippar
Purattum
Kutha
Pallukkatu
Jamdet Nasr
Irnina
Tigris
Kut
Babylon
Kish
Borsippa
Nippur
Shat al-Garraf
Najaf
Kish Branch
Adab
Kisurra
Kut present cities
Larsa ancient cities
Jidr
Hindiyh
Isin
Zabalam
Shuruppak
Umma
Girsu
Hilla
Lagash
Uruk
Nina
Bao Tibra
Larsa
Euphrates
Nasyriyah
Ur
(Gibson, 1972 Oates, 979 Adams, 1981 Saggs,
1988 Northedge et al., 1990 Cole Gasche,
1998)
Eridu
Laham
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• Factors that may affect settlement distribution
• Avulsion rate (abrupt vs gradual abandonment of
  
• former channel)
• Avulsion frequency (number of avulsions during
  certain
• period of time)
• Avulsion style (reoccupational vs
  progradational)
• - reoccupation flow occupies channel previously
• existing channel on floodplain (e.g. former
  major
• channel or smaller stream channel)
• - progradation avulsion belt is deposited
• following avulsion, followed by formation of
• a new single channel
• Channel pattern following avulsion
• (single channel or multiple channel system)

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• Three scenarios resulting from avulsions with
  different
• implications for settlement distribution
• A. Single channel with crevasse splays or
• two-channel system in case of gradual avulsion
• B. Progradational avulsion followed by
  development avulsion belts
• C. Gradual and/or frequent avulsions followed by
  long-lasting coexistence (102-103 yrs) of many
  active channels and avulsion belts.

crevasse splay
avulsion belt
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Ancient Mesopotamian Cities

• Were located on river banks and surrounded by
  their countryside with corona of irrigation
  agriculture
• sustaining area per individual was estimated
  between 0.5-1.5 ha/person
• daily travel distances from city to countryside
  did not exceed 3-4 km for maximum agricultural
  productivity

(Jacobsen, 1958 Oppenheim, 1969 Chisholm, 1970
Johnson, 1973 Adams Nissen, 1972 Adams,
1985).
Reconstruction of UR (www.taisei.co.jp/cg_e/anc
ient_world/ur/aur.html)
Large city with about 40,000 inhabitants required
200-600 km2 of nearby irrigated land
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Gravity-flow irrigation

• Channels confined by levees flowing higher than
  elevation of surrounding floodbasins

• Artificial channels or levee breaks at crevasse
  channels are used as intake points for irrigation
  water

• Irrigational enclaves develop within distal
  levee and crevasse splays where soils are better
  drained and undergo less salinization
• Relatively small naturally- irrigated area
  needed for rural settlements, e.g. 5-15 km2 for
  a settlement of 1000.

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Sizes of settlements in relation to sizes of
naturally-irrigated area
(gravity-flow irrigation)
Crevasse splays - size several km2 - splay
with size of 10km2 can support up to 200
people - everyday walking distance did not have
to exceed 3-4 km Avulsion belts - size several
100 km2 - avulsion belt with size of 600km2 can
support more than 40,000 people - everyday
travel out and in the city could be by boat
along anastomosed channels - anastomosed
channels could be kept flowing by desilting and
regulating of inflow and outflow channels
rural
10 km
city
new channel
avulsed channel
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rural
Consequences of avulsion scenarios for
settlement distribution A. Single channel no
increase in settlement size, some increase in
settlement number in case of gradual avulsion,
rural settlements at crevasse splays under
natural conditions in desert climate extensive
canal construction is needed to increase the
irrigated area of floodplain B. Avulsion belt
local increase in naturally-irrigated area of
floodplain and settlement size, city and rural
settlements at crevasse splays C. Multiple
channels with crevasse splays, many avulsion
belts dramatic increase in naturally-irrigated
area of floodplain, increase in settlement number
and settlement sizes, many cities and rural
settlements.
urban
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before 6000 BP, Ubaid period prior to major
onset of settlement
Zagros Mountains
Tigris
Jazira Plateau
folded Cenozoic rocks
?
Persian Gulf
Euphrates
Arabian Platform
alluvial fan
eolian sediments
Paleozoic rocks
(Larsen Evans, 1978 Adams, 1981 Aqrawi,
1996, 1999, 2001)
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6000-5300 BP, Late Ubaid-Middle Uruk periods
Zagros Mountains
Tigris
?
Jazira Plateau
folded Cenozoic rocks
Persian Gulf
Euphrates
Hammar Formation
Arabian Platform
alluvial fan
Paleozoic rocks
eolian
(Larsen Evans, 1978 Adams, 1981 Aqrawi, 1996,
1999, 2001)
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5300-3600 BP, LateUruk-Old Babylonian periods
Zagros Mountains
Tigris
Jazira Plateau
?
?
folded Cenozoic rocks
Persian Gulf
Euphrates
alluvial fan
Hammar Formation
Arabian Platform
Paleozoic rocks
eolian
(Larsen Evans, 1978 Adams, 1981 Aqrawi, 1996,
1999, 2001)
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3600-1000 BP, Cassite-mid Islamic
Zagros Mountains
Tigris
Jazira Plateau
Folded Cenozoic rocks
Euphrates
marsh sediments
Hammar Formation
Arabian Platform
alluvial fan
Paleozoic rocks
eolian
alluvial fans
abandoned deltaic plains
marsh
settlements a) rural, b) urban
canals
valleys
eolian
(Larsen Evans, 1978 Adams, 1981 Aqrawi, 1996,
1999, 2001)
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Preliminary Conclusions
http//www.upennmuseum.com/ cuneiform.cgi
- avulsions and resulting channel and
sedimentation patterns affected the distribution
and sizes of irrigated floodplain, quality of
soils, and, therefore, settlement patterns -
progradational avulsions with avulsion belts
created conditions for local increase in
naturally-irrigated area with well-drained soils,
generation of food surpluses and population
migration toward area possibly leading to
appearance of urban settlements - during and
after abandonment of avulsion belts and multiple
channel networks in favor of two-channel or
single-channel system, extensive canal
construction was required to maintain urban and
many rural settlements, eventually abandoned
(probably due to increased inefficiency) during
mid-Islamic period.