Modelling the risk of deterioration at earthen heritage sites in drylands

Abstract

The variable climatic and environmental conditions associated with dryland regions can cause rapid erosion to both natural and man‐made earthen structures. Whilst there is a long history of research into the evolution of erosional landforms such as yardangs, little research has investigated how dryland processes influence the erosion of built structures. Earthen heritage sites located in arid and semi‐arid environments experience rapid deterioration caused by exposure to environmental drivers such as wind and rain. Understanding how these environmental drivers interact with each other and cause deterioration to earthen material is vital for successful conservation strategies. To address this need, we present the Vegetation and Sediment TrAnsport model for Heritage Deterioration (ViSTA‐HD) that simulates the risk of polishing, pitting and slurry on earthen heritage in a spatially specific manner. A technical description of the model is provided, and sensitivity and validation tests are reported. The model is then used to simulate the risk of deterioration occurring over centennial timescales at a Suoyang Ancient City, located in semi‐arid northwest China. The modelled risk of deterioration is in good agreement with deterioration patterns found at Suoyang, with the risk of polishing predominantly occurring around the wall edges, areas at risk of pitting echoing the dune formation and the risk of slurry occurring in drape‐like patterns down the wall face. Consequently, ViSTA‐HD is a powerful and versatile model that can be used to help inform our understandings of long‐term interactions between dryland processes and deteriorative impact on earthen structures. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

Deterioration risk of dryland earthen heritage sites facing future climatic uncertainty

“…The risk of deterioration is determined using three factors: (1) the environmental conditions impacting on the given area of the wall; (2) the extent to which areas around the given area of the wall also experience the deterioration; and (3) previous deterioration on the given area of the wall. More details on the deterioration module can be found in Richards et al 21 .…”

“…Eighty percent vegetation coverage was implemented by increasing the proportion of randomly distributed vegetation elements in the model space. In all model runs, vegetation was assumed to remain the stable as at Suoyang image analysis has shown vegetation cover to remain stable over a decadal period 21 .…”

“…This paper applies a novel numerical modelling method to evaluate the potential risk of deterioration under future climate and conservation scenarios. We use the Vegetation and Sediment TrAnsport model for Heritage Deterioration (ViSTA-HD), a cellular automaton model developed by the authors that couples environmental and heritage deterioration processes 21 .…”

“…This enables us to detect changes across wall faces under different climate and conservation scenarios. Richards et al 21 provide a detailed explanation and extensive set of verification and validation tests for ViSTA-HD, with empirical data supporting the model formulation. The "Methods" section in this paper provides further description of the model.…”

“…1d). The modelled climatic and ecological conditions were reflective of present-day conditions at Suoyang unless otherwise stated and were informed by previous studies undertaken at the site 16,21 . Results of deterioration risk were similar for the two modelled walls, so we only present results from the 50 m wall in the main manuscript; results for the 10 m are provided in the Supplementary Information.…”