Assessment of post-tsunami disaster land use/land cover change and potential impact of future sea-level rise to low-lying coastal areas: A case study of Banda Aceh coast of Indonesia

© 2019 The objective of this study is to investigate the impact of the projected sea-level rise to the coastal land use/land cover (LULC) at a disaster-prone coastal area, encompassing an engineering time-scale, based on a couple of sea-level rise scenarios. We investigate the Banda Aceh coast, a low-lying coastal area vulnerable to multiple hazards such as tsunamis and co-seismic land subsidence, which is typical along the Indonesian coastlines. Three sets of multi-temporal Google Earth Engine images acquired in 2004 (pre-tsunami December 2004), 2011 and 2017 were utilized to obtain the areal coverage of various types of LULC. The scenarios of coastal inundation were pre-determined at elevation +1.0 m and +1.5 m projecting the sea-level rise in the next couple centuries. Aquaculture ponds, buildings and bare land are the top three most pre-dominant land covers in Banda Aceh coast. The finding of this study reveals that the aquaculture ponds are at the highest risk to the future sea-level rise, and potentially contribute to the unproductive seawater inundated area. The bare land which has a huge potential to be converted into settlement area (buildings, housing, etc.), experienced remarkable loss due to both future inundation scenarios. The coastal area of Banda Aceh in the next couple of centuries, thus, will be highly vulnerable to the projected sea-level rise, providing the fast-growing and ever-expanding built environment very close to the coastline. A sustainable coastal management taking into account the disaster risk should, therefore, be incorporated within the decision making for the protection of the coastal area

From rapid visual survey to multi-hazard risk prioritisation and numerical fragility of school buildings

Regional seismic risk assessment is paramount in earthquake-prone areas, for instance, to define and implement prioritisation schemes for earthquake risk reduction. As part of the Indonesia School Programme to Increase Resilience (INSPIRE), this paper proposes an ad hoc rapid-visual-survey form, allowing one to (1) calculate the newly proposed INSPIRE seismic risk prioritisation index, which is an empirical proxy for the relative seismic risk of reinforced concrete (RC) buildings within a given building portfolio; (2) calculate the Papathoma Tsunami Vulnerability Assessment (PTVA) index, in any of its variations; (3) define one or more archetype buildings representative of the analysed portfolio; (4) derive detailed numerical models of the archetype buildings, provided that the simulated design is used to cross-check the model assumptions. The proposed INSPIRE index combines a baseline score, calibrated based on fragility curves, and a performance modifier, calibrated through the analytic hierarchy process (AHP) to minimise subjectivity. An attempt to define a multi-hazard prioritisation scheme is proposed, combining the INSPIRE and PTVA indices. Such a multi-level framework is implemented for 85 RC school buildings in Banda Aceh, Indonesia, the most affected city by the 2004 Indian Ocean earthquake–tsunami sequence. As part of the proposed framework, two archetype buildings representative of the entire portfolio are defined based on the collected data. Their seismic performance is analysed by means of non-linear static analyses, using both the analytical simple lateral mechanism analysis (SLaMA) method and numerical finite-element pushover analyses to investigate the expected plastic mechanisms and derive displacement/drift thresholds to define appropriate damage states. Finally, non-linear dynamic analyses are performed to derive fragility curves for the archetype buildings. This paper demonstrates the effectiveness of the INSPIRE data collection form and proposed index in providing a rational method to derive seismic risk prioritisation schemes and in allowing the definition of archetype buildings for more detailed evaluations/analyses

Data for: Assessment of post-tsunami disaster land use/land cover change and potential impact of future sea-level rise to low-lying coastal areas: A case study of Banda Aceh coast of Indonesia

The data provided here include the delineation of Land Use / Land Cover (LULC) of Banda Aceh coastal system. The LULC type polygon maps produced by a delineation of discernible objects on the individual satellite image of 2004, 2011 and 2017, and stored them in polygon shape format. The delineation was performed by using the unsupervised LULC classification scheme, digitized from each of the individual high-resolution satellite images of 30 x 30 cm pixels. We identified and validated objects and patches specific to different types of LULC from each satellite image based on our familiarity with the study area. Three sets of high-resolution satellite images acquired on 23rd June 2004 (pre-tsunami December 2004), 1st March 2011 and 14th May 2017 retrieved from the Google Earth Pro - Digital Globe, were utilized for LULC delineation using ArcGIS software. Each of the acquired satellite images was already geo-referenced and spatially rectified. Eight types of LULC, including the aquaculture, bare land, building area, lagoon, mangrove, rice field, river and sea, were delineated for the individual satellite images. The quantifiable land use and land cover were delineated as polygons of aquaculture, bare land, building area, lagoon, mangrove and rice field. Figure 4 displays the polygon maps of the LULCs delineated from the high-resolution satellite images

Barrier Islands Resilience to Extreme Events: Do Earthquake and Tsunami Play a Role?

Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier islands are surprisingly resilient to extreme storm events. At present, little is known about barrier systems’ resilience to seismic events triggering tsunamis, co-seismic subsidence, and liquefaction. The objective of this study is, therefore, to investigate the morphological resilience of the barrier islands in responding to those secondary effects of seismic activity of the Sumatra–Andaman subduction zone and the Great Sumatran Fault system. Spatial analysis in Geographical Information Systems (GIS) was utilized to detect shoreline changes from the multi-source datasets of centennial time scale, including old topographic maps and satellite images from 1898 until 2017. Additionally, the earthquake and tsunami records and established conceptual models of storm effects to barrier systems, are corroborated to support possible forcing factors analysis. Two selected coastal sections possess different geomorphic settings are investigated: (1) Lambadeuk, the coast overlying the Sumatran Fault system, (2) Kuala Gigieng, located in between two segments of the Sumatran Fault System. Seven consecutive pairs of comparable old topographic maps and satellite images reveal remarkable morphological changes in the form of breaching, landward migrating, sinking, and complete disappearing in different periods of observation. While semi-protected embayed Lambadeuk is not resilient to repeated co-seismic land subsidence, the wave-dominated Kuala Gigieng coast is not resilient to the combination of tsunami and liquefaction events. The megatsunami triggered by the 2004 earthquake led to irreversible changes in the barrier islands on both coasts