Assessing human impact on alluvial fan development: a multidisciplinary case-study from Lower Khuzestan (SW Iran)

Abstract

This paper presents a multidisciplinary approach for studying the evolution of an alluvial fan system in Lower Khuzestan (SW Iran). The study draws on previously collected data from geological and archaeological field campaigns and new data derived from the interpretation of satellite imagery and historical textual sources. Three alluvial fans were identified, successively deposited by the Jarrahi river in progressively downstream/westward direction. Judging from archaeological and historical evidence, the successive phases appear to coincide with a relocation of settlement and irrigation activities. The distributary system of the present-day fan developed over a period of less than four centuries. It is suggested that management of levee breaks by man played a key role in such rapid fan development and in maintaining extremely low gradients. Judging from the extensive patterns of ancient irrigation canals, human activity also played an important role in the formation of the earlier fans.

The role of long‐term human impact on avulsion and fan development

“…The alluvial depositional history of the river Jarrahi and the development of its three spatially separated alluvial fans have been reconstructed in detail (Walstra et al , ). It has been demonstrated that human‐intervention had an important impact on the evolution of the different fans.…”

“…Previous case‐studies highlighted the substantial effect of human actions (notably the construction of large‐scale irrigation works) on the river patterns and sedimentation history of the region (Alizadeh et al ; Verkinderen, ; Walstra et al , ; Heyvaert et al , ). This paper is not intended to replicate this work, but rather to re‐evaluate the case‐studies in the light of controls and mechanisms of avulsions, with particular focus on human action.…”

“…Fluvial fans are scenes of recurrent avulsions and owe their existence and typical cone‐shaped depositional landform to avulsion activity (Gohain and Prakash, ; Horton and DeCelles, ; Makaske et al , ; Leier et al , ; Assine, ; Walstra et al , , Walker and Fattahi, ; Arzani, ). They are typically located at mountain fronts where rivers are released from their confinement and discharge conditions promote frequent avulsions.…”

Characteristics of direct human impacts on the rivers Karun and Dez in lowland south-west Iran and their interactions with earth surface movements

“…A variety of methods were applied, including field survey (Kavanagh, 2009), geomorphological and sedimentological fieldwork (Goudie et al, 1990;Jones et al, 1999a), and analysis of topographical information, geological maps, and remote sensing images. This included the use of a unified LandsatTM and CORONA database of processed and geo-referenced imagery using ERDAS IMAGINE and ArcGIS ® software (Walstra et al, 2010a(Walstra et al, , 2011. All of the data was compiled and used with data from previous work in the region to demarcate areas of human activities, structural geology, and river characteristics which included river hydrology, sedimentology, morphology, migration, and longitudinal profiles.…”

“…Other factors, such the constraining influence of the River Jarrahi delta to the east (Fig. 7), may have been more influential in the persistence of this near-straight river course (Walstra et al, 2010a;Heyvaert et al, 2013).…”