Suggestions for large-scale, postdisaster reconstruction involving indigenous populations: a participatory approach to recovery after Typhoon Morakot

Purpose The participatory method, a major factor for a successful post-disaster reconstruction (PDR) project, is applied in various stages of the PDR. However, the application of this method for PDR involving indigenous populations is underexplored. Therefore, this paper aims to analyze the critical factors that can influence the participatory PDR in the indigenous context. Design/methodology/approach Two large-scale, indigenous, post-disaster relocation projects after the 2009 Typhoon Morakot were selected as case studies. The qualitative and quantitative methodology (semi-structured interview and questionnaire) were applied in the research. Findings A participation-friendly policy, community organization, the extent of damage, flexibility of nongovernmental organizations, understanding of the participatory concept and mutual trust were found to be essential factors that profoundly influence participation in PDR projects. Originality/value This study contributes by providing guidelines for future participatory PDR projects, especially in the indigenous context.

Evaluating the Landslide Stability and Vegetation Recovery: Case Studies in the Tsengwen Reservoir Watershed in Taiwan

The sediment yield from numerous landslides triggered in Taiwan’s mountainous regions by 2009 Typhoon Morakot have had substantial long-term impacts on the evolution of rivers. This study evaluated the long-term evolution of landslides induced by 2001 Typhoon Nari and 2009 Typhoon Morakot in the Tsengwen Reservoir Watershed by using multiannual landslide inventories and rainfall records for the 2001–2017 period. The landslide activity, vegetation recovery time, and the landslide spatiotemporal hotspot analyses were used in the study. Severe landslides most commonly occurred on 35–45° slopes at elevations of 1400–2000 m located within 500 m of the rivers. The average vegetation recovery time was 2.29 years, and landslides with vegetation recovery times exceeding 10 years were most frequently retrogressive landslide, riverbank landslides in sinuous reaches, and the core area of large landslides. The annual landslide area decline ratios after 2009 Typhoon Morakot in Southern Taiwan was 4.75% to 7.45%, and the time of landslide recovery in the Tsengwen reservoir watershed was predicted to be 28.48 years. Oscillating hotspots and coldspots occupied 95.8% of spatiotemporal patterns in the watershed area. The results indicate that landslides moved from hillslopes to rivers in the 2001–2017 period because the enormous amount of sediment deposited in rivers resulted in the change of river geomorphology and the riverbank landslides.

Characteristics of the Near-Ground Typhoon Morakot

Two WJ-3 anemometers placed at the same height on the top of an architectural engineering building in Wenzhou University are used to determine the wind speed of Typhoon Morakot during its landing in real time. This study aims to explore Typhoon Morakot’s wind field characteristics, including mean wind speed, probability density distribution of fluctuating wind speed, power spectral density, correlation analysis, and coherence, on the basis of data measured by the two anemometers. Results show that the probability density distribution of the fluctuating wind speed of the typhoon follows the Gaussian distribution, and the measured cross-power spectrum of fluctuating wind speed is in good agreement with the modified Karman spectrum. The autocorrelation decreases with the increase in time interval (τ). The longitudinal autocorrelation coefficient decays rapidly with the increase in τ, and the lateral autocorrelation coefficient decays at an unchanged rate. The exponential attenuation coefficients of the longitudinal and transverse fluctuating wind speeds increase with the increase in the mean wind speed, and their mean values are 10.86 and 15.33, respectively. The change trends of the coherence coefficients of the two wind speed components with the mean wind speed are the same. The measured coherence coefficients of the two wind speed components are in good agreement with the exponential function.

Badland landscape response to individual geomorphic events

Landscapes form by the erosion and deposition of sediment, driven by tectonic and climatic forcing. The principal geomorphic processes of badland – landsliding, debris flow and runoff erosion – are similar to those in full scale mountain topography, but operate faster. Here, we show that in the badlands of SW Taiwan, individual rainfall events cause quantifiable landscape change, distinct for the type of rainfall. Typhoon rain reduced hillslope gradients, while lower-intensity precipitation either steepened or flattened the landscape, depending on its initial topography. The steep topography observed in our first survey is inconsistent with the effects of any of the rainfall events. We suggest that it is due to the 2016 Mw 6.4 Meinong earthquake. The observed pattern in the badlands was mirrored in the response of the Taiwan mountain topography to typhoon Morakot in 2009, confirming that badlands offer special opportunities to quantify natural landscape dynamics on observational time scales.

Spatiotemporal Hotspots and Decadal Evolution of Extreme Rainfall-Induced Landslides: Case Studies in Southern Taiwan

The 2009 Typhoon Morakot triggered numerous landslides in southern Taiwan, and the landslide ratios in the Ailiao and Tamali river watershed were 7.6% and 10.7%, respectively. The sediment yields from the numerous landslides that were deposited in the gullies and narrow reaches upstream of Ailiao and Tamali river watersheds dominated the landslide recovery and evolution from 2010 to 2015. Rainfall records and annual landslide inventories from 2005 to 2015 were used to analyze the landslide evolution and identify the landslide hotspots. The landslide recovery time in the Ailiao and Tamali river watershed after 2009 Typhoon Morakot was estimated as 5 years after 2009 Typhoon Morakot. The landslide was easily induced, enlarged, or difficult to recover during the oscillating period, particularly in the sub-watersheds, with a landslide ratio > 4.4%. The return period threshold of rainfall-induced landslides during the landslide recovery period was <2 years, and the landslide types of the new or enlarged landslide were the bank-erosion landslide, headwater landslide, and the reoccurrence of old landslide. The landslide hotspot areas in the Ailiao and Tamali river watershed were 2.67–2.88 times larger after the 2009 Typhoon Morakot using the emerging hot spot analysis, and most of the new or enlarged landslide cases were identified into the oscillating or sporadic or consecutive landslide hotspots. The results can contribute to developing strategies of watershed management in watersheds with a dense landslide.

Maintaining Quality of Care among Dialysis Patients in Affected Areas after Typhoon Morakot

Natural disasters have negative health impacts on patients who need dialysis in affected areas. Severely affected areas are usually rural, with limited basic infrastructure and a population without optimal dialysis-specific care after a disaster. A population-based longitudinal case–cohort study enrolled 715,244 adults from the National Health Insurance Registry who lived in areas affected by a major natural disaster, Typhoon Morakot, in 2009. The observation period was from 2008 to 2011. A total of 13,268 patients (1.85%) had a history of end-stage renal disease (ESRD). Of the ESRD patients, 1264 patients (9.5%) received regular dialysis. Only eight patients missed dialysis sessions in the first month after the disaster. Compared to the moderately affected areas, the incidences of acute cerebrovascular and cardiovascular diseases were higher in patients in severely affected areas. Male dialysis patients aged 45–75 years had a higher mortality rate than that of the general population. Among the affected adults receiving regular dialysis, patients with diabetes (adjusted hazard ratio (aHR): 1.58, 95% confidence interval (CI): 1.20–2.08) or a history of cerebrovascular disease (aHR: 1.58, 95% CI: 1.12–2.21), chronic obstructive pulmonary disease (COPD) or asthma (aHR: 1.99, 95% CI: 1.24–3.17) in moderately affected areas had significantly elevated mortality rates. Additionally, among dialysis patients living in severely affected areas, those with a history of cerebrovascular disease (aHR: 4.52 95% CI: 2.28–8.79) had an elevated mortality rate. Early evacuation plans and high-quality, accessible care for cardiovascular and cerebrovascular diseases are essential to support affected populations before and after disasters to improve dialysis patients’ health outcomes.

Mechanisms and activity of deep-seated landslides at Tienchih and Yakou (S Taiwan) revealed by structural geology and remote sensing

&lt;p&gt;Deep-seated gravitational slope deformations (DSGSD) gained increasing attention in Taiwan due to their catastrophic impacts on lives and infrastructures during Typhoon Morakot in 2009, when over 2700 mm of rainfall in 5 days were recorded. As the main Taiwan island is located on a complex convergent plate boundary, available data suggest that the island&amp;#8217;s strong tectonic activity has contributed, along with its subtropical climate and intense human activity, to the onset and destabilization of deep-seated landslides. These are widespread in high-relief mountain areas where Miocene to Eocene meta-sandstone and slate successions outcrop. Slopes at Tienchih (Lalong River of Kaohsiung) and Yakou (few km east in Taitung County) were affected by significant slope collapses and impending instabilities after the heavy precipitation of Typhoon Morakot. This led to severe damages and closure of the South Cross Island Highway No.20, a critical roadway connecting the western and eastern sides of S Taiwan, where continuing slope instability has been observed after 2009. At Tienchih, 240 mm of displacement over an area of 6.7 ha were recorded in 2016 by continuous GPS measurements after a heavy rainfall event. At Yakou, the middle slope sector including the road experienced a major collapse in 2018. At both sites, morpho-structural evidence identified in 1-m resolution LiDAR DEMs suggest that long-term slope deformations occurred well before catastrophic slope destabilization. This is supported by spectacular gravitational deformation structures (i.e. kink folds and shear zones), well exposed at Yakou, and by continuous slow movements detected at Tienchih by multi-temporal TCPInSAR analyses on ALOS/PALSAR images (2007-2011). On the other hand, dense vegetation and limited rock outcrops make an accurate assessment of the geometry, controls, mechanisms and style of activity of these landslides difficult. To overcome this difficulties, we carried out a systematic geomorphological mapping of the two areas through ortho-photos and HRDEMs derived from aerial LiDAR (2012 and 2019), and field surveys to characterize the local structural geology (ductile and brittle features), rock mass strength and gravitational morpho-structures. We performed a local-scale analysis of displacement patterns and rates by combining traditional radar interferometry (D-InSAR on ALOS and Sentinel-1 imagery), improved TCPInSAR analyses, GPS data, Digital Image Correlation between DEMs and change detection analysis of LiDAR point clouds. Our results suggest that long-term progressive failure of slopes was promoted by high tectonically-forced erosion rates and constrained by inherited ductile structures. These preconditioned the location, size and mechanisms of slope sectors more prone to catastrophic failure due to intense rainfall and river bank erosion. A systematic characterization of long-term slope deformation can thus provide key information to assess the hazard related to deep-seated landslides in Taiwan.&lt;/p&gt;