The alluvial landscapes of southern Mesopotamia during the Early Dynastic period (c. 2900–2350 BCE) were structured by dense networks of rivers, canals, and wetlands that shaped both irrigation practices and patterns of mobility. While ancient waterways are often modeled as conduits of movement and exchange, they also constituted significant barriers to overland accessibility, particularly within low-relief floodplain environments. This paper presents a GIS-based least-cost path (LCP) approach to modeling accessibility between three Early Dynastic sites—Umma, Zabalam, and Tell Shimd—using slope-derived friction surfaces based on a 5 m DEM, combined with hypothetical reconstructions of irrigation canals and river courses.
Multiple hydrological scenarios are tested, including topographically plausible water networks derived from DEM-based flow accumulation and alternative canal configurations modeled under slope constraints and archaeological plausible traces on the field. These waterways are incorporated into cost surfaces primarily as high-friction or impassable features, with controlled crossing points used to simulate fords or bridges. The resulting models demonstrate how different reconstructions of irrigation and drainage systems significantly alter accessibility patterns between settlements, even within a landscape characterized by minimal topographic variation.
By foregrounding uncertainty and explicitly modeling waterways as barriers as well as components of irrigation infrastructure, this study offers a reproducible framework for integrating hydrological features into mobility modeling and highlights how irrigation systems structured both agricultural production and spatial interaction in Early Dynastic southern Mesopotamia.

First Author: Fatemeh Javanmardi

Co-Authors: Tadeáš Červík

Keywords:
Irrigation Systems
Least-cost Path Analysis
Waterways as Barriers
Accessibility
DEM