Consiglio Nazionale delle Ricerche

Tipo di prodottoPoster
TitoloAutomatic Delineation of Slope Units and Terrain Classification of Italy (poster)
Anno di pubblicazione2019
Autore/iM. Alvioli, F. Guzzetti, I. Marchesini
Affiliazioni autoriConsiglio Nazionale delle Ricerche, Istituto di Ricerca per la Protezione Idrogeologica, via Madonna Alta, 126 - 06128, Perugia, Italy
Autori CNR e affiliazioni
  • inglese
AbstractAutomatic delineation of slope units and terrain classification of Italy Automatic subdivision of landscapes into terrain units, in large areas and with homogeneous criteria, remains a challenge. Slope units (SUs) are irregular terrain units bounded by drainage and divide lines, with the requirement of maximizing geomorphological homogeneity within a single unit and heterogeneity between different ones (Guzzetti et al., 1999). SUs are suitable to describe a variety of processes: to assess different natural hazards, for hydrological and erosion modelling, for geo-environmental, ecological, forestry, agriculture, and in general for studies requiring the identification of homogeneous terrain domains facing distinct directions. Nevertheless, their use has been hampered because of the lack of reliable software for their automatic delineation. For a given digital landscape, no unique SU partition exists. Any such partition is characterized by a granularity i.e., the size distribution of the SUs. Granularity varies in different landscapes and for different purpose of the terrain partition. We recently developed the r.slopeunits software (Alvioli et al, 2016), which can draw slope unit polygons on a digital surface. It provides an unambiguous and reproducible definition of slope units based on quantitative hydrologic and topographic criteria, allowing for a flexible yet well-defined SU delineation through an adaptive algorithm. The code is designed to quickly produce results on large areas. It requires a digital elevation model and a few input parameters, whose values must be optimized in a sound way, by means of multiple software runs and a proper objective function to be maximized. We propose a parameter-free SU map of the entire Italian territory, containing about 300,000 SU polygons. We optimized the map considering only objective morphometric quantities. To assess the validity of the nation-wide SU partition, we classified the whole of Italy into different categories using a clustering procedure, initialized using only morphometric properties of the SUs. We compared the classification form clustering with zonal statistics of independent quantities: terrain elevation and slope, drainage density and lithology. The analysis confirmed that the SU partition was geomorphologically sound, suggesting that the proposed method is effective for a general-purpose SU delineation of a large, complex and heterogeneous landscape. The whole SU map is available for download (CNR-IRPI URL).
Lingua abstractinglese
Altro abstractQuantitative geomorphological and environmental analysis requires the adoption of mapping units, welldefined spatial domains providing local boundaries to aggregate environmental and morphometric variables and to perform calculations. Grid cells, typically aligned with a digital elevation model, are the standard mapping unit choice [1, 2]. Slope Units (SU) represent a wiser choice than grid cells. SU are irregular terrain partitions delimited by drainage and divide lines, also maximizing geomorphological homogeneity within each unit and heterogeneity between neighbouring units. SU bear a stronger relation with the underlying topography, absent in grid cells [3]. We developed a software for the automatic delineation of SU, given a digital elevation model [4]. Delineation is adaptive, in that SU of different shape and, most importantly, different size, are delineated according to local terrain characteristics. Moreover, we devised an optimisation procedure for the size of SU, suitable for study areas of arbitrarily large size and with varying degrees of heterogeneity. Our research group applied SU delineation inmany scientific papers studying different areas of the world and for different purposes, including landslide susceptibility zonation [4, 5, 6, 7], aggregation of results of cell-based slope stability models [8, 9], earthquake-induced landslide prediction [10, 11], and optimization of landslide mapping from satellite images [12]. Many other groups used the software for similar applications. The method, applied to the whole of Italy, resulted in a map containing about 330,000 SU polygons of different sizes and shapes, and with varying local granularity [13, 14]. Fitness of the map was assessed through a cluster analysis for terrain classification of Italy We show that the clusters, selected by a k-means algorithm, provide a non-trivial classification of the territory in terms of morphometric and lithological quantities. We suggest the use of the SU map for different terrain zonations, including landslide susceptibility modeling, hydrological and erosion modelling, geo-environmental, ecological, forestry, agriculture and land use/land cover studies requiring the identification of ho- mogeneous terrain domains facing distinct directions.
Lingua altro abstractinglese
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Verificato da refereeSì: Nazionale
Stato della pubblicazionePublished version
Indicizzazione (in banche dati controllate)-
Parole chiaveSlope units, terrain classification, optimization
Link (URL, URI)
Titolo convegno/congressoCongresso Nazionale Parma 2019 - Il tempo del pianeta Terra e il tempo dell'uomo: le geoscienze tra passato e futuro
Luogo convegno/congressoParma
Data/e convegno/congresso16-19/09/2019
Titolo parallelo-
Note/Altre informazioni-
Strutture CNR
  • IRPI — Istituto di ricerca per la protezione idrogeologica
Moduli/Attività/Sottoprogetti CNR
  • DTA.AD003.294.001 : RFI-SERVICE
Progetti Europei-
Automatic Delineation of Slope Units and Terrain Classification of Italy
Descrizione: poster PDF
Tipo documento: application/pdf