In a most recent article, a team of climatologists and historians around Ulf Büntgen has proposed the identification of a “Late Antique Little Ice Age” in the period from 536 to 660 AD which was characterised by significant socio-political upheavals and catastrophes such as volcanic eruptions and plague epidemics. Among the extreme events not included into their scenario by Büntgen et alii is the severe flood which in 628 AD affected what is now modern-day Southern Iraq, then the core province of the mighty Sasanian Empire, which was not to survive the following decades.
by Johannes Preiser-Kapeller, OEAW (Johannes.Preiser-Kapeller@oeaw.ac.at)
In his “Book of the Conquests of Lands”, the 9th century Arab historian al-Balādhurī reported: “(…) in the year 7 or 6 of Hegira [628/629] the Euphrates and the Tigris had a considerable flood, such as had never been seen before or after: large breaches opened that [the Sasanian Great King] Khusro [II] Parvez tried to close, but the water was stronger and reached the low country, submerging villages and crops and several land districts in this place. Khusro [II Parvez] came to the site in person to block the breaches: he laid a pile of silver on a leather tablecloth and put to death those workers who did not work hard enough (it is said that on a single dike he put under the cross, in one day, forty of those who worked there), but he could not stop the water. At the same time, the Arabs invaded Iraq and the Persians became henceforth preoccupied by war, to the point that the breaches grew larger without anyone worrying about it: the landowners in the villages were powerless to block them, so large were they, so the marshes grew in extent.” Al-Baladhuri X: 453-454 (transl. Hitti)
Great King Khusro II, called Parvez (“The Victorious”) at that time had ruled over the Sasanian Empire, which in its core encompassed modern-day Iran and Iraq, for almost 40 years (since 590 AD). Most of this time, he had waged war against the neighbouring Eastern Roman Empire. Since 602 and especially after 610 AD, Sasanian armies had occupied the richest provinces of their traditional imperial rival in Syria, Palestine and Egypt; two years before the flood of the Tigris, Persian troops even had stood at the Asian side of the Bosporus vis-à-vis the Roman capital of Constantinople. Yet in the face of the natural disaster, the Great King seemed almost as helpless as a mere mortal.
Fig.: Taq-e Bostan in Iran: relief of Great King Khusro II in the centre with the goddess Anahita to the left and the god Ahura Mazda to the right.
In the narrative of al-Balādhurī and other Arab historians, the incipient invasion of the troops of the newly emerging Arab umma of Islam added up to the crisis of the Sasanian Empire and hindered the Persians to take successful measures against the flooding. But as a matter of fact, the Arab invasion started in earnest only four years later in 632. More probably, it was a turning of tides in the war with Rome which impeded a more effective handling of the disaster. Since 622 AD, the Roman Emperor Heraclius (r. 610-641) had been able to perturb the not yet consolidated rule of the Persians over Eastern Anatolia and the Caucasus region in a series of audacious campaigns. In Armenia and Georgia, he found valuable new clients. Furthermore, the Emperor allied himself with the Khanate of Western Turks, who controlled the Steppes to the north of the Caucasus and Iran in Central Asia. In 627, Turkish horsemen devastated the border provinces of the ancient Sasanian realm while Heraclius defeated a Persian army at Niniveh in Northern Iraq and marched towards the residence of Khusro II in Dastagird near the capital of Ctesiphon (near modern-day Baghdad), to which the Great King had to flee.
Fig: Late Antique Mesopotamia and the approx. area affected by the flood of 628 AD to the south of Wāsit; places in brackets were founded later under Arab rule (map: J. Preiser-Kapeller, 2016).
In this most critical situation, disaster struck. The short and long term impacts of the flood of 628 AD are described in the work of the Persian geographer Ibn Rusta of the 10th century: “The river cut through the earth until it started flowing past Wāsit and its waters flowed into al-Batā´ih [the marshes]. At that time [before the flood], al-Batā´ih were cultivated lands that continued without interruption up to the land of the Arabs (…) and (…) up to the land of Maisān. The water took possession of the low-lying areas, and the higher areas became islands. These places are known to this day in al-Batā´ih (…). Ruins are still visible under water in the al-Batā´ih depression, because the water is motionless and clear; this demonstrates the area used to be [solid] land. And the original marshes in which the Tigris water gathered, before it shifted to the area of Wāsit, were in Jūhā, in the area between al-Madār and Abdasī; when the Tigris shifted, the water was cut off from these marshes, and they became desolate deserts. Whoever passes through them in summer, suffers fierce sand storms.” (transl. Verkinderen 2015, 54).
Fig.: A street in Baghdad after a flood in October 2015.
The disaster thus affected the region not only on a short term basis, but permanently and significantly modified the landscape; a vast area to the south of the town of Wāsit became known as al-Batā´ih (the marshes) for centuries. Wide areas of cultivated land were lost, settlements disappeared and people had to leave their homes. In his magisterial new study on the waterways of Iran and Iraq in the early Islamic period, Peter Verkinderen describes the hydrological background to this catastrophe: “(…) both Tigris and Euphrates breached their banks at numerous places in 628. (…) Like the Euphrates – and many other meandering rivers – the Tigris regularly breached its bank in its lower reaches, and over the course of centuries created levees, raised riverbeds that rise up to several metres above the plain. A breach (or crevasse) occurs when part of this raised bank of the river collapses, usually during high water periods. The force of the water rapidly widens the gap, but because the river is located above the level of the surrounding plain, the water also starts to erode the levee in a vertical direction, cutting a channel through the sides of the levee that is lower than the original riverbed; at worst, the river can abandon its bed entirely (avulsion). The results of such a breach are dramatic: it becomes next to impossible to make the river return to its former – raised – bed, and the river inundates a large area at the side of the levee where the breach occurred; depressions can be turned into lakes or marches. (…) Moreover, the levee of the former bed becomes a dike that prevents the water from reaching the area at the other side of the levee. In a worst-case scenario, a breach permanently inundates the fertile areas one side of the levee, and entirely deprives the area on the other side of the levee from water. This appears to be exactly what happened with the Tigris.” (Verkinderen 2015, 54).
Fig.: The marshes in the delta region of Euphrates and Tigris today
The hydrological causes for this disaster can be found in the climatic conditions of the “Late Antique Little Ice Age“ as recently identified by Ulf Büntgen and his colleagues: various sources document a series of extremely cold and snow-rich winters in the regions of the waterheads of Euphrates and Tigris and their tributaries in Eastern Anatolia, Armenia and the Zagros mountains in the years 623 to 628 AD (cf. for instance Telelis 2004; Haldon 2014). While these harsh weather conditions allowed the Roman army to outmanoeuvre their Persian foes in the Transcaucasian areas, the abundance of melt water resulted in the catastrophic floods of the Euphrates and the Tigris. But as Peter Christensen has outlined in his now classic volume on the “Decline of Iranshahr” (1993), disaster in 627/628 AD struck the Persian provinces at the same time also as another wave of the so-called Justinianic plague, which time and again reduced populations across the Mediterranean and the Near East since the 540s (the reign of Emperor Justinian I). The losses of populations due to the epidemic and of productive land due to the flood further destabilised the Sasanian polity already on the verge of defeat from the hand of the Romans; according to the estimates of Christensen, the area of Iraq contributed 50 % of the Empire´s revenues – and half of these may have been lost due to the deluge of 628 AD.
Fig: The trajectories of temperature and the series of political upheavals in the “Late Antique Little Ice Age” between 536 and 660 AD as reconstructed by Büntgen et al. 2016
The most prominent victim of this combination of military and natural disasters became Great King Khusro II himself: in February 628, he was deposed by leading members of the aristocracy and later killed in prison. He was replaced by his son Kavadh II Siroe, who was able to negotiate peace with Emperor Heraclius, but died under unclear circumstances already in September 628. The regime now ran out of the rudder: in the following four years, not less than seven kings and queens succeeded to the Sasanian throne before Yazdegerd III (r. 632-651) established a longer lasting rule again. But he was the last of the Persian Great Kings and lost his crumbling empire to the Arabs, who first conquered Iraq and then entire Iran.
The Sasanian Empire had come to an end after more than 400 years. The flood of 628 AD of course was not the sole trigger of its demise. Already the rule of Khusro II in 590 AD had started with civil war and internal unrest; as Parvaneh Pourshariati has demonstrated in her monograph of 2008, the socio-political framework of Sasanian power as such was less centralised and stable as hitherto assumed. But the series of climate-induced disasters (weather extremes, epidemics and flood) together with the devastating war with the Romans and later the Arabs in the 620s-640s definitely tested the Persia´s resilience beyond its limits (as they almost did also for the Eastern Roman Empire). The Sasanian Empire thus may be added to the “victims” of the “Late Antique Little Ice Age”.
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