Modeling Antecedent Soil Moisture to Constrain Rainfall Thresholds for Shallow Landslides Occurrence

Rainfall-triggered shallow landslide events have caused losses of human lives and millions of euros in damage to property in all parts of the world. The need to prevent such hazards combined with the difficulty of describing the geomorphological processes over regional scales led to the adoption of empirical rainfall thresholds derived from records of rainfall events triggering landslides. These rainfall intensity thresholds are generally computed, assuming that all events are not influenced by antecedent soil moisture conditions. Nevertheless, it is expected that antecedent soil moisture conditions may provide critical support for the correct definition of the triggering conditions. Therefore, we explored the role of antecedent soil moisture on critical rainfall intensity-duration thresholds to evaluate the possibility of modifying or improving traditional approaches. The study was carried out using 326 landslide events that occurred in the last 18 years in the Basilicata region (southern Italy). Besides the ordinary data (i.e., rainstorm intensity and duration), we also derived the antecedent soil moisture conditions using a parsimonious hydrological model. These data have been used to derive the rainfall intensity thresholds conditional on the antecedent saturation of soil quantifying the impact of such parameters on rainfall thresholds.

Geographical distribution of the weather stations and landslide events for the study area. The graph in the inset shows the monthly distribution of landslides in Basilicata from 2001 to 2018.

How to cite: Lazzari, M., M. Piccarreta, R. L. Ray and S. Manfreda, Modelling antecedent soil moisture to constrain rainfall thresholds for shallow landslides occurrence, Landslides edited by Dr. Ram Ray, IntechOpen, pp. 1-331, (10.5772/intechopen.92730) 2020. [Link]

Modelling Antecedent Soil Moisture to Constrain Rainfall Thresholds for Shallow Landslides

Rainfall-triggered shallow landslides have caused losses of human life and millions of euros in damage to property in all parts of the world. The need to prevent such phenomena combined with the difficulty to describe the geo-physical processes over large scales led to the adoption of empirical rainfall thresholds derived from the observed relationship between rainfall mean intensity and duration and landslide occurrence. These thresholds are generally obtained neglecting the role of the antecedent moisture conditions that should be taken into consideration. Therefore, traditional approaches that neglect such parameter may have a limited value in the early-warning systems. In the present manuscript, we explored the role of antecedent soil moisture on critical rainfall intensity–duration thresholds highlighting its impact.This study was carried out using a record of 326 landslides occurred in the last 18 years in the Basilicata region (southern Italy). Besides the ordinary data (i.e. rainstorm intensity and duration), we also derived the antecedent moisture conditions using a parsimonious hydrological model. We found that antecedent soil saturation plays a crucial role on landslide triggering, which may support the improvement of forecast systems. In particular, this parameter seems to control rainfall thresholds that tend to assume lower values when a rainfall event is occurring on a saturated soil.

How to cite: Lazzari, M., Piccarreta, M., and Manfreda, S.: The role of antecedent soil moisture conditions on rainfall-triggered shallow landslides, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2018-371, under review, 2018.

The role of antecedent soil moisture conditions on rainfall-triggered shallow landslides

Rainfall-triggered shallow landslides have caused losses of human life and millions of euros in damage to property in all parts of the world. The need to prevent such phenomena combined with the difficulty to describe the geo-physical processes over large scales led to the adoption of empirical rainfall thresholds derived from the observed relationship between rainfall intensity/duration and landslide occurrence. These thresholds are generally obtained neglecting the role of the antecedent moisture conditions that should be taken into consideration. In the present manuscript, we explored the role of antecedent soil moisture on the critical rainfall intensity-duration thresholds highlighting its critical impact. Therefore, traditional approaches that neglect such parameter may have a limited value in the early-warning systems. This study was carried out using a record of 326 landslides occurred in the last 18 years in the Basilicata region (southern Italy). Besides the ordinary data (i.e. rainstorm intensity and duration), we also derived the antecedent moisture conditions using a parsimonious hydrological model.

How to cite: Maurizio Lazzari, Marco Piccarreta, Salvatore  Manfreda, The role of antecedent soil moisture conditions on rainfall-triggered shallow landslides, Natural Hazards and Earth System Sciences Discussions (doi: https://doi.org/10.5194/nhess-2018-371), 2018. [pdf]

HYDROLOGICAL AND GEOLOGICAL HAZARDS IN BASILICATA

Basilicata is known for the highest frequency of extreme hydrological and geological events. Several landslides and floods have extensively affected the region because of its geological characteristics and dynamics of precipitation producing extensive damage to regional urban areas and infrastructures. In this work, an analysis of extreme events occurred from 1925 to 2015 in Basilicata region is carried out in order to characterize their spatial and temporal evolution. This allowed us to identify the most critical periods and the areas most frequently affected by events that have caused damage on territory.

How to cite: Dal Sasso, S.F., S. Manfreda, G. Capparelli, P. Versace, C. Samela, G. Spilotro, M. Fiorentino, La pericolosità idraulica e geologica della regione BasilicataL’Acqua, n.3, 77-85, 2017. [pdf]