Angelo Doglioni

Evolutionary polynomial regression to alert rainfall-triggered landslide reactivation

The derivation of an alert model for landslide risk management is a paramount problem for those sites which are affected by complex landslides involving strategic infrastructures as well as towns. This is a quite common scenario all over the world and then it is a primary problem for the management of geomorphological risk. Along the Adriatic Coast of south Italy, Petacciato landslide is peculiar, since it showed 11 reactivations between 1924 and 2009. It is a deep-seated landslide, and the history of its reactivations shows that even if generally related to quite abundant rainfall periods, there is no clear correlation between rainfall events and reactivations. For this reason, here, an analysis based on a data-driven evolutionary modeling technique is attempted, in order to identify an alert model based on cumulative rainfall heights. Modeling results are quite interesting and encouraging, since they are able to provide landslide forecasting whereas no false positive are ever returned. This work shows the results of this attempt as well as an analysis of the input to the modeling approach, in order to identify which are those cumulative rainfall heights which are physically sound with respect to the particular landslide.

Inferring groundwater system dynamics from hydrological time-series data

Abstract The problem of identifying and reproducing the hydrological behaviour of groundwater systems can often be set in terms of ordinary differential equations relating the inputs and outputs of their physical components under simplifying assumptions. Conceptual linear and nonlinear models described as ordinary differential equations are widely used in hydrology and can be found in several studies. Groundwater systems can be described conceptually as an interlinked reservoir model structured as a series of nonlinear tanks, so that the groundwater table can be schematized as the water level in one of the interconnected tanks. In this work, we propose a methodology for inferring the dynamics of a groundwater system response to rainfall, based on recorded time series data. The use of evolutionary techniques to infer differential equations from data in order to obtain their intrinsic phenomenological dynamics has been investigated recently by a few authors and is referred to as evolutionary modelling. A strategy named Evolutionary Polynomial Regression (EPR) has been applied to a real hydrogeological system, the shallow unconfined aquifer of Brindisi, southern Italy, for which 528 recorded monthly data over a 44-year period are available. The EPR returns a set of non-dominated models, as ordinary differential equations, reproducing the system dynamics. The choice of the representative model can be made both on the basis of its performance against a test data set and based on its incorporation of terms that actually entail physical meaning with respect to the conceptualization of the system. Citation Doglioni, A., Mancarella, D., Simeone, V. & Giustolisi, O. (2010) Inferring groundwater system dynamics from hydrological time-series data. Hydrol. Sci. J. 55(4), 593–608.

Geomorphometric analysis based on discrete wavelet transform

This work presents a geomorphometric approach for outlining anomalies of the topographic surface that may be related to geological structures or to geomorphological phenomena. It is based on 2D discrete wavelet transform of digital elevation models. This transform is used to extract singularities of a series of data. This is specifically applied to a digital elevation model, in order to get its detail coefficients and to have evidence about their variations and values. In particular, this approach can be helpful for the delineation and identification of landforms singularities, like landslides and geological structures. The potential and effectiveness of this approach is shown by an application to a case study about a large deep-seated landslide, located at the central-south front of the Apennine in South Italy.

Analysis of the Rainfall Preceding the Activation of the Large Maierato Landslide in 2010

This work focuses on the impact of the antecedent rainfall as triggering factor of the large landslide occurred in Maierato (south Italy) on February 15, 2010. According to previous studies by Guerricchio et al. (Tecniche per la difesa dall’inquinamento – 31° Corso di aggiornamento, pp 661–706, 2010) the predisposing factor of the landslide is an ancient deep-seated gravitational slope deformation that significantly affected landforms, drainage networks and infiltration processes of the whole slope where Maierato is located. Here after a brief introduction of the landslide according to the aforementioned study, a hydrological analysis of the rainfall preceding the landslide is presented. The analysis aims at evaluating the exceptionality and some peculiar characters of rainfall, which may be considered among the triggering factors of the landslide.

Quantitative Geomorphological Analysis Based on Wavelet Transforms

The identification and quantitative study of important geological discontinuities, like those related to large landslides constitutes a paramount problem, which claims for a careful, detailed and, if possible, quantitatively based geomorphologic analysis. Numerical geomorphic analyses represent an interesting approach to these studies, allowing for a detailed and pretty accurate identification of hidden topographic anomalies that may be related to large landslides or other hidden geological structures. Geomorphic numerical analyses herein presented, are performed on the digital elevation model, based on the 2D discrete wavelet transform. This analysis is applied to a case study related to the middle-south Apennine at the front of the Apennine, whereas a really large deep-seated large landslide has been previously identified on the base of different geomorphic analysis. Finally, the analysis emphasizes some peculiar aspect of the buried front of the Apennine, which can potentially bias the landslide.

Relationships between rain and displacements of an active earthflow: a data-driven approach by EPRMOGA

Inclinometer and piezometer measurements have been carried out since 2005 in a slow active earthflow in a clay shale formation of the Italian Southern Apennines. Previous studies outlined the main geometrical and kinematic features of the landslide and the pore pressure response to rainfall. Displacement rates seem to depend on the hydrological conditions as suggested by their seasonal variations. The availability of long time series of data, in some periods recorded in continuum, allows the use of a data mining approach to evaluate the relations among displacement rates in different points of the landslide, and between displacement rates and rainfall. To define such relations, the evolutionary modelling technique EPRMOGA, based on a genetic algorithm, has been used in this paper. The results give a deeper insight into the landslide behaviour on the one hand and, on the other hand, show the reliability of the technique, also in building up management scenarios. In particular, the results show that the landslide displacement rates in different points of the slip surface, although characterized by different values, are linearly dependent and thus have the same time trend, supporting the hypothesis of a constant soil discharge mechanism of movement. Piezometric data in single points cannot be used, in the considered case, to forecast displacements. The obtained relations allow to quantify the displacement rate variations due to contemporary rainfall. The influence of past rainfall is shown to decrease exponentially with temporal distance. Furthermore, the EPRMOGA simulations seem to confirm that there are no other dominant causes, besides rainfall, responsible of displacement rate variations in time.

Notes on morphological characters of ephemeral streams in Apulia region, south Italy

This work introduces an investigation on the peculiarity of morphological characteristics of the ephemeral streams of the central part of Apulia, in south-east of Italy. In particular, the analysis is focused on their morphological features, allowing to improve the knowledge about their origin and genesis. Moreover, a comparison between the ephemeral streams of the Murgia area and those of north Salento is proposed. These two groups of ephemeral stream share interesting similarities in term of stream length, catchment area, and climatic condition, but are located in different geological situations. The earlier group crosses the cretaceous limestone bedrock, outcropping in Murgia upland, the latter crosses quaternary deposits of Brindisi plateau. It is envisaged that ephemeral streams of Murgia even if located in quite geologically ancient rocks show morphological characteristics typical of a stream evolution at a really earlier stage differently from those of north Salento located in quaternary deposits. This is apparently unmotivated, since it should be the opposite. Therefore a likely reason for this may be a different genesis of ephemeral streams of Murgia.

A Simple Model for Passive Failure Compression Structure at the Toe of Landslide

The toe of landslides is subject to compression stresses induced by the upward sliding masses and often characterized by a co mpression structure. These structures can evolve in passive toe thrust, which bias the geomorphologic evolution of the toe zone, particularly for prevailing longitudinal dimension landslide. This work presents a simple analytic model of the passive thrust at the toe of landslide based on the infinite slope approach to stability analysis. It is based on the analysis of the state of stresses according to Mohr circle representation and can be implemented also into a spreadsheet and making it possible to evaluate the form of failure surface at the toe of the landslide and the shear strength contribution to the factor of safety of a landslide.

Success of Reclamation Works and Effects of Climatic Changes in Taranto Area: South Italy

The paper presents some considerations on the potential influence of climatic changes on the effectiveness and the success of reclamation works made between the 19th and the 20th century in some areas of the west bound of Taranto (South Italy), characterized by large swamps for centuries. Historical documents underline the difficulty to make effective and successful reclamation works in the area of Taranto, as in other areas of the Mediterranean basin because swamps were continuously supplied by upward groundwater flow from the powerful deep karst aquifer. Success were obtained during Thirties thanks to improvement in technical knowledge and design technics, but these successes were obtained in a period characterized by rainfall decreasing. This paper aims at emphasizing that successes in reclamation works were obtained during a period of rainfall decreasing that affected Taranto area and all southern Italy between the 19th and the 20th century. Rainfall decreasing induced a lowering of groundwater table and a reduction of swamp supply, favoring the success of reclamation works.

Evolutionary Data-Driven Modelling of Salento Shallow Aquifer Response to Rainfall

Data-driven techniques are among the most powerful approaches to model environmental phenomena. Evolutionary modelling constitutes and interesting approach able to combine the regressive feature of data-driven modelling with the power of evolutionary optimization. Here an evolutionary data-driven paradigm is used in order to model aquifer response to rainfall. The aquifer is shallow and located in south-east Apulia, south Italy, for which a long and reliable time series of monthly water table levels, measured in monitoring wells, are available. The identified models are consistent with past studies and with the hydrogeological characteristics of the aquifer, allowing for explicating the main rainfall components influencing the water table and the lag between rainfall and water table oscillations.