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Recent increases in urbanization and tourism threaten the viability of UNESCO world heritage sites across the globe. The Angkor world heritage site located in southern Cambodia is now facing such a challenge. Over the past two decades, Angkor has seen over 300,000% growth in international tourist arrivals, which has led to uncontrolled development of the nearby city of Siem Reap. This study uses remote sensing and GIS to comprehend the process of urban expansion during the past 14 years, and has applied the CA-Markov model to predict future urban expansion. This paper analyzes the urban pressure on the Angkor site at different scales. The results reveal that the urban area of Siem Reap city increased from 28.23 km2 in 2004 to 73.56 km2 in 2017, an increase of 160%. Urban growth mainly represented a transit-oriented pattern of expansion, and it was also observed that land surfaces, such as arable land, forests, and grasslands, were transformed into urban residential land. The total constructed land area in the core and buffer zones increased by 12.99 km2 from 2004 to 2017, and 72% of the total increase was in the buffer zone. It is predicted that the built-up area in Siem Reap is expected to cover 135.09 km2 by 2025 and 159.14 km2 by 2030. The number of monuments that are most likely be affected by urban expansion is expected to increase from 9 in 2017 to 14 in 2025 and 17 in 2030. The urban area in Siem Reap has increased dramatically over the past decade and monuments continue to be decimated by urban expansion. This paper urges closer attention and urgent actions to minimize the urban pressure on the Angkor site in the future. [ABSTRACT FROM AUTHOR]

The sustainability of Angkor World Heritage site (Cambodia) has been of increasing concern due to rapid socioeconomic development of the surrounding region including the booming city of Siem Reap. We interpret findings from satellite radar interferometry (InSAR) motion fields for the period 2007–2017 to derive new insights into the dynamics of the relationship between land subsidence, groundwater extraction and monument stability. Evolution of motion trends along with hydraulic heads indicated that the surface in the archaeological zone was stable up to 2011, followed by a mild subsidence during 2011–2017, primarily impacted by unregulated tourism development. Spatially decline of groundwater table beneath Siem Reap City could, in the future, threaten the stability of monuments. We developed a model that predicted that surface subsidence in the central archaeological zone could reach up to −3.6 to −3.8 mm/yr by 2021 if a 6% annual increase of tourists and the resulting demand for groundwater resources continued. A tourism carrying capacity below 2.5 million per year may be sustainable to prevent the emergence of hydrological problems that could exacerbate the risk of significant land subsidence and consequences for monument stability. This study is a clear illustration of the value of InSAR space-eye combined with ground-based measurements for monitoring potential hazards and modelling conservation states of World Heritage sites in order to improve preparedness critical for mitigating future threats. • Understanding of the water crisis and sustainability of Angkor site is challenging. • Satellite InSAR and ground-based data evaluate the over-tourism impact in Angkor. • Surface motions and hydraulic heads indicate the emergence of hydrological problems. • The developed model predicts future motion trends in the archaeological landscape. • This study demonstrates the value of InSAR-eye in monitoring heritage sites. [ABSTRACT FROM AUTHOR]