In March 2010 incessant rainfall reactivated the landslide at Montaguto, in the province of Avellino, which blocked the railway line from the capital and Naples to Puglia.
The continuous rainfalls of last March triggered off the landslide at Montaguto, in the province of Avellino, once again. Guido Bertolaso, Head of the Department is Commissioner Delegate for the Monteguto emergency nominated by ordinance 3868 on 21 April last. This is how the civil protection coordination begins for making the area safe and controlling the landslide that had interrupted the railway line connecting the capital/Naples with Puglia.
After a meeting held on 19th March at the civil Protection Department, Regione Campania requested a State of Emergency in order to accomplish the new urgent works. The declaration of State of Emergency was signed by the Prime Minister on 16 April.
This landslide had already moved in the past. A State of Emergency was declared by Prime Minister Decree on 12 May 2006 and on 13 July the same year, ordinance 3532 established the first urgent works, completed in June 2007, and appointed the president of Regione Campania as Commissioner Delegate.
In spite of these works, in September last year the landslide started to move again, involving the main road S.S. n. 90 “Delle Puglie" once again, up until the Benevento-Foggia section of the railway line was closed on 10 March 2010 subsequent to being invaded by landslide material.
On 25 May, the State Railways, the operator assigned by the Commissioner Delegate to restore traffic back to normal along the Benevento-Foggia railway line, informs that regular service will be restored – along this section – in early June.
The main road SS 90 by-pass is opened on 10th July after the works, coordinated by civil protection technical experts, of taking away the debris, levelling out the roadbed, adjusting the guardrail, tar sealing and repairing and replacing the signs and signals also horizontal, along a section of road 480 metres long and almost 8 metres wide.
An integrated monitoring system was installed to assess the speed of the landslide, to be able to measure the surface movement of the landslide and programme the actions to be taken for assuring the safety of the area and infrastructures involved.
On 29th April 2010 the DST-UNIFI Competence Centre installed a land based radar system (GBInSAR LiSALab) (together with the ElleGi srl – LiSALab companies).
This system continually records data and processes a radar image every 4 minutes to be able to monitor the instability in real time. As the instrument has been installed on the opposite side to the landslide it is also able to monitor the lower portion and foot of the landslide.
The displacement of the landslide is measured by examining the interferograms, that is the difference between two radar images.
Average speeds vary between 2.5 metres day, measured on the summit of the foot of the landslide (sector B), to 1.1 metres per day, observed in the right hand sector of the foot of the landslide involved by the re-profiling works on the hillside (sector D).
The CNR-IRPI Operations Centre, a geomonitoring group in the Turin section, started up a topographic monitoring system to measure the speed of displacement in various areas of the central part of the slide.
The monitoring systems installed are:
- a complete robotized station installed at the front of the landslide, working since 29/04/2010. The input gives no indication of major displacements.
- a complete robotized station on the right flank of the accumulation area of the phenomenon, where material is currently being removed and re-profiling works are in progress since 30/04/2010. The monitoring data shows that the principal landslide phenomenon travels at a speed oscillating between 2.0 and 2.60 meters per day, whilst the secondary slide phenomenon travels at a speed of between 3.60 and 4.20 metres per day.
- a complete manually controlled station plus relative network of topographic posts installed in the central area, to the left of the area of accumulated material and re-profiling works in progress since 4/05/2010. The data shows that displacement speeds oscillate between 1.40 and 1.90 metres per day, at a steady speed; the values are less than centimetre/hour from an altimetry point of view.
The Commissioner Delegate had started up a series of operations, through the contractor Angelo Pepe, to channel the waters from the lakes and sources of water along the central part of the landslide, away from the landslide.
The purpose of these operations was to guarantee safe conditions for the work sites and to improve the overall conditions of the destabilized slope.
The works were carried out with the assistance of the DST-UNIFI, CNR-IRPI Operations Centres, Sannio University and the Foggia 11th Engineer Sapper Corps Regiment.
Job 1: altitude 500 m above sea level
At the altitude of 500 m above sea level the waters coming from the Schiamone River basin flowed directly into the central part of the landslide. A considerable part of the water in the central-terminal part of the landslide was eliminated by diverting these waters and channelling them valley-wards under controlled conditions. The works comprised: construction of an interception and retaining harness for the "Schiavone" stream waters, laying a water pipe (about 850m) to channel the waters towards River Cervaro and interception works to divert minor surface watercourses into the canal.
The typology of the works was established by the conditions of accessibility to the sites, time imposed by the events and above all by the necessity to avoid any interference between works at the work site and calamity in progress.
The works in fact served to mitigate the effects of the water circulating on the surface and just under the surface of the landslide to reduce the risk in the foot areas, where removal and profiling works were in progress to restore the communication network (railway and SS 90 main road).
Job 2: altitude 700 m above sea level
A drainage trench in gabions was dug to collect the waters from under the surface and those circulating on the surface and channel them towards the "Tre Confini" stream at a distance from the landslide.
The trench was positioned at an average depth of about 5 m from ground level and where the landslide canal has a reduced section, for geological reasons, and is at the right height for channelling the waters into the adjacent water basin. The water circulation above the landslide was partly restored and a considerable amount of the water flowing to feed the land on the move in the central-upper part of the slope was eliminated with these works.
Job 3: cleaning and repairing the "Laghetto delle rane" drainage canal
The works comprised deepening and re-profiling the canal, ablation of the pond and temporarily restoring the drainage canal to River Cervaro. The area also underwent forestry clearance works and dead vegetation was removed to allow the water to flow freely.
The waters coming from the water sources orographically to the left, which by running into a pond called "Laghetto delle rane" continually fed the land on the move, were deviated away from the landslide by these works
Job 4: Lake "Maggiore" siphon
To empty the landslide lake formed in a hollow (750 m above sea level) after the calamitous events, the Foggia 11th Engineer Sapper Corps Regiment built a system of siphons with light flyover pipes coming out in the "Tre confini" stream away from the landslide.
Job 5: horizontal drainage
Being impossible to use standard means for intercepting and draining the waters from the foot of the landslide in the area, sub-horizontal drainage holes were made with the “no-dig” method: through a drill leaving from undisturbed areas and crossing the central part of the landslide to connect up a special drain.