Including informal housing in slope stability analysis – an application to a data-scarce location in the humid tropics

Abstract

Abstract. Empirical evidence from the humid tropics shows that informal housing can increase the occurrence of rainfall-triggered landslides. However, informal housing is rarely accounted for in landslide hazard assessments at community or larger scales. We include informal-housing influences (vegetation removal, slope cutting, house loading, and point water sources) in a slope stability analysis. We extend the mechanistic model CHASM (Combined Hydrology and Stability Model) to include leaking pipes, septic tanks, and roof gutters. We apply this extended model (CHASM+) in a region of the humid tropics using a stochastic framework to account for uncertainties related to model parameters and drivers (including climate change). We find slope cutting to be the most detrimental construction activity for slope stability, and we quantify its influence and that of other destabilising factors. When informal housing is present, more failures (+85 %) are observed in slopes that would otherwise have had low landslide susceptibility and for high-intensity, short-duration precipitations. As a result, the rainfall threshold for triggering landslides is lower when compared to non-urbanised slopes and comparable to those found empirically for similar urbanised regions. Finally, low cost-effective “low regrets” mitigation actions are suggested to tackle the main landslide drivers identified in the study area. The proposed methodology and rainfall threshold calculation are suitable for data-scarce contexts, i.e. when limited field measurements or landslide inventories are available.

Computational Modeling of Hyperpolarizing Astrocytic Influence on Cortical Up-Down State Transitions

“…To delineate the dynamical regimes in which the model was bistable as well as exhibited spontaneous Up-Down transitions, we performed a stability analysis similar to the one in (19). The resultant Eq (23) and (24), thus, delimited the bistable dynamical regime as shown in Fig 3. Low values of β and θ E are expected to give rise to a regime of persistently high firing rates, i.e., a stable Up state.…”

“…We did SA for ten parameters and characterized the highly sensitive parameters as free parameters compared to the Moyse model. It was implemented using the Sensitivity Analysis For Everyone (SAFE) toolkit, an open-source program (23).…”

Interferometric Synthetic Aperture Radar (InSAR) and field‐based observations of rainfall‐triggered landslides from the November 2021 storm, Gisborne/Tairāwhiti, New Zealand

“…Emerging evidence cautions that land‐use change may equal, or in some instances exceed, the impact of climate change in affecting the temporal and spatial occurrence of landslides (Ozturk et al, 2022). Indeed, growth and land development for residential properties and related infrastructure often neglects the natural constraints that are bestowed by the local environment (Bozzolan et al, 2020). Thus, in addition to the rainfall outlined above, site‐specific anthropogenic factors also appear to influence slope failures in the Gisborne region, namely: (1) vegetation removal, (2) inadequate slope stabilisation and drainage, (3) slope loading and (4) topographic changes/cutting.…”

Contrasting Population Projections to Induce Divergent Estimates of Landslides Exposure Under Climate Change

“…In addition, the interaction between risk components has been investigated in some studies (Depicker et al., 2021; Ozturk et al., 2022). Findings indicate that the distribution of population and transport infrastructure, apart from influencing landslide exposure as elements at risks, could interact with changes in landslide hazard (Bozzolan et al., 2020; Brenning et al., 2015). For instance, the unplanned sprawl of urbanization in mountainous areas would not only lead to an increased exposed population and buildings, but also to changes in the morphology, hydrological or material properties of the landslides, and thus changes in the landslide hazard for individual or regional landslides (Dille et al., 2022; Ozturk et al., 2022), due to the associated changes in land use, especially the destruction of vegetations, the cutting of slopes for road construction or housing, and the excavation at the foot of the slopes (Bozzolan et al., 2020; Depicker et al., 2021; Dille et al., 2022; Ozturk et al., 2022).…”