Water-Risk Management in Tchogha Zanbil World Heritage Site in Iran, With a Focus on the Ancient Management System

Abstract

Abstract. Water-risk management is one of the most challenging issues in the conservation of earthen sites, because of the inherent weakness of earth to moisture, and also the severe damage after rainfall as a result of a combination of many factors in the deterioration processes. In Tchogha Zanbil World Heritage Site (WHS) in Iran, this problem causes more damage due to the heavy rains that impact the site in a short period of time. The property encompasses a vast area, which makes regular maintenance more difficult. Also, there are insufficient strategies for controlling water runoff on the structures. Archaeological studies have revealed an ancient system for managing surface water at this site which could be compatible and adaptable for further development of the current management system. This study aims to present sustainable approaches in managing water-risk in the Tchogha Zanbil WHS, by identifying the authenticity values, investigating the problems and challenges in the current water-management system, and more importantly, assessing ancient strategies for controlling water, based on archaeological evidence.

Assessment of vulnerability and site adaptive capacity to the risk of climate change: the case of Tchogha Zanbil World Heritage earthen site in Iran

“…Based on UNESCO-WHC reports (1995, 2000), heavy rainfall has been one of the most destructive factors in Tchogha Zanbil, in recent years. The water-related erosion observed in Tchogha Zanbil is also well-discussed in previous work (Nakhaei and Correia, 2020) as follow:The development of small gullies and channels due to the sleep slope of the upper parts of the Ziggurat is introduced, as the first step for deterioration;In the response to soil erosion, small holes become large cavities and penetration of rainwater occurs;Soil erosion, subsidence and compaction to a significant depth;Subsidence after saturation where there is no sloping;Massive destruction of the brick façade due to penetration of water in the exit of the pits and cavities, at the junction of the adobe structure and brick façade;Salt crystallization and efflorescence due to evaporation of penetrated moisture in the adobe structure of ziggurat, directing the soluble salts to the brick façade;Loss of gutter efficiency due to destruction of the upper parts of the ziggurat and due to the changes to the ziggurat drainage system andRaising vulnerability to atmospheric downpours due to loss of brick façade which was designed for protecting the central structure.…”

“…On the other hand, it can be considered that Tchogha Zanbil has a considerable adaptive capacity. In fact, Elamites were aware of water vulnerability in some parts of Tchogha Zanbil's ziggurat and had designed and elaborated a water management system, to protect it against extreme events, such as heavy rains (Mofidi, 2007; Nakhaei and Correia, 2020). Even today, ancient techniques can provide resilience, even if they serve a different purpose in society, operate within a different organizational structure or are resilient for different reasons (Kaptijn, 2018).…”

“…In this regard, although the physical and managerial sensitivity of Tchogha Zanbil expose it to severe risk of climate change (Table 1), the adaptive capacities decreased the rate of vulnerability, especially physical sensitivity which consists of the highest scores. For instance, calculating the inlet/outlet capacity of gutters as Elamite architecture did, and adding new gutters if it seems needed (based on topography), as well as using ceramic channels for conducting water flow and controlling gully formation in upper parts (Nakhaei and Correia, 2020). Moreover, managerial sensitivity plays an important role in exposing the site to drought and desertification; however, long-term planning and using sustainable methods for controlling drought accelerating factors are the key elements at national level (see Table 2).…”

“…Based on the climate change trend map of Khuzestan, Tchogha Zanbil is located in an area with a classification of very severe hazard of climate change, which is described by significant changes in temperature (>4 °C increase in temperature for 100 years) and significant changes in decreasing of climate index trend toward drier condition (Masoudi and Elaheesahar, 2016). In Tchogha Zanbil, the study of intensity-duration-frequency revealed that the possibility of precipitation considered high destructive occurs at a frequency of 98 mm in 15 min, with different return periods (Nakhaei and Correia, 2020).…”

“…In addition, the upper parts of the ziggurat become the section of the structure that is the most vulnerable to atmospheric downpours since its protective brick facade is missing (Nakhaei and Correia, 2020). Figure 4 confirms the high sensitivity of this structure when unprotected sections of the adobe structure overlap with high-risk areas for water erosion.…”