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

Shallow soil slips are a significant hydrogeological hazard which could affect extended areas of the high-gradient mountainous landscape. Their triggering is highly dependent on the rainfall water infiltration and its further redistribution, as well as the characteristic properties of the soil itself. The complex interaction between those factors generates a considerable degree of uncertainty in the understanding of the governing processes. In this work, we take a small step further towards the untangling of those intricate relationships through observation. The results of a set of 20 downscaled shallow land mass failures are analysed through a principal component analysis and a further detailed look at the resulting parametric trends. Moreover, electrical resistivity tomography measurements are added up to the interpretation of experimental data, by providing a glimpse on the rainfall water infiltration process at the subsurface level. The outcome of this work implies that the coupled interaction between rainfall intensity, hydraulic conductivity and soil moisture gradient is governing the stability of soil and while rainfall intensity and duration are essential instability predictors, they must be integrated with antecedent moisture and site-specific characteristics. A tentative comparison of the dataset with existing rainfall thresholds for shallow landslide occurrence suggests the potential application of experimental tests for thresholds' definition or validation under the appropriate dimensional analysis. A dimensional analysis indicated the interconnection of parameters intrinsic to the problem, and the significance of scale effects in performing a downscaled simulation of land mass failure.

Section: Introductionmentioning

confidence: 99%

Investigation on the Role of Water for the Stability of Shallow Landslides—Insights from Experimental Tests

Ivanov

Arosio

Tresoldi

et al. 2020

“…Three critical levels-normal, moderate, and high-are defined daily for each zone on the basis of pluviometric thresholds. The latter are identified for characteristic durations of foreseen rainfall events (3,6,12,18,24,48,72,96, and 120 h) and for return times of 2, 5, and 20 years.…”

Section: Discussionmentioning

confidence: 99%

“…The GRIB files with the forecasts are downloaded and pre-processed; 3. For each duration (3,6,12,18,24,48,72,96, 120 h), from the current time to the next 36 h, the DSS checks whether the threshold has been exceeded. Recorded precipitation and forecasts are accumulated for a time span of 3 h and compared with the critical values.…”

Section: Discussionmentioning

confidence: 99%

“…To Basilicata region, in Southern Italy, is one of the most vulnerable in the national territory, with nearly 50% of the towns classified as high risk for landslides or floods [16][17][18], and a dense drainage network that supplies around 90% of the water resources for public use to the Puglia region [19]. The Basilicata region covers an area of 9992 km 2 in Southern Italy.…”

Section: Case Studymentioning

confidence: 99%

See 1 more Smart Citation

The GEOframe-NewAge Modelling System Applied in a Data Scarce Environment

Bancheri

Rigon

Manfreda

2019

Self Cite

In this work, the semi-distributed hydrological modeling system GEOframe-NewAge was integrated with a web-based decision support system implemented for the Civil Protection Agency of the Basilicata region, Italy. The aim of this research was to forecast in near real-time the most important hydrological variables at 160 control points distributed over the entire region. The major challenge was to make the system operational in a data-scarce region characterized by a high hydraulic complexity, with several dams and infrastructures. In fact, only six streamflow gauges were available for the calibration of the model parameters. Reliable parameter sets were obtained by simulating the hydrological budget and then calibrating the rainfall-runoff parameters. After the extraction of the flow-rating curves, six sets of parameters were obtained considering the different streamflow components (i.e., the baseflow and surface runoff) and using a multi-site calibration approach. The results show a good agreement between the measured and modeled discharges, with a better agreement in the sections located upstream of the dams. Moreover, the results were validated using the inflows measured at the most important dams (Pertusillo, San Giuliano and Monte Cotugno). For rivers without monitoring points, parameters were assigned using a principle of hydrological similarity in terms of their geology, lithology, and climate.

“…The heavy rains and floods caused a powerful and spectacular landslide event because of the anthropic removal of the old drainage network. Lazzari et al [7] have explored the role of antecedent soil moisture on the critical rainfall intensity-duration thresholds highlighting its critical impact. This study was carried out using a record of 326 landslides that occurred in the last 18 years in the Basilicata region, Southern Italy.…”

Section: Introductionmentioning

confidence: 99%

Combining TRIGRS and DEBRIS-2D Models for the Simulation of a Rainfall Infiltration Induced Shallow Landslide and Subsequent Debris Flow

Hsu

Liu

2019

TRIGRS revealed the responses of the total pressure heads and factors of safety with a depth change under a rainfall infiltration occurring on the Daniao tribe’s hill. The depth distribution of the collapsed zone could be identified under the condition where the factors of safety Fs = 1, and the results could calculate the area and volume. Afterward, DEBRIS-2D used TRIGRS’s results to assess the hazard zone of the subsequent debris flow motion. In this study, the DTM variation analysis results from both of before and after the Daniao tribe’s landslide are used to validate TRIGRS’s simulation, the area and the volume of the collapse zone within 8% and 23% errors, respectively. The real disaster range was depicted from the aerial photo used to validate the hazard zone simulation of DEBRIS-2D within 25% errors. In spite of that, the hazard zone from the simulation still included the real disaster range. The combining method for a rainfall infiltration induced a shallow landslide and subsequent debris flow, which was well-matched on a real disaster range on the Daniao tribe’s hill. Therefore, we believe that the TRIGRS and DEBRIS-2D combining methods would provide a better solution for an assessment of a rainfall infiltration inducing shallow landslide and subsequent debris flow motion. TRIGRS could, therefore, provide the area and depth distribution of the collapsed zone, and DEBRIS-2D could use TRIGRS’s results for subsequent debris flow hazard assessment. Furthermore, these results would be of great help in the management of slope disaster prevention.