Remote Sensing (Earth Sciences)

INSAR TIME-SERIES ANALYSIS FOR MANAGEMENT AND MITIGATION OF HYDROGEOLOGICAL RISK IN URBAN AREA

by Florence ReSeT

CIGNA F. , DEL VENTISETTE C. , LIGUORI V. , CASAGLI N.

Mapping and DOWNFLOW simulation of recent lava flow fields at Mount Etna

by Simone Tarquini

Tarquini S., Favalli M.
2011, J. Volcanol. Geoth. Res. 204, 27-39

In recent years, progress in geographic information systems (GIS) and remote sensing techniques have allowed the... more In recent years, progress in geographic information systems (GIS) and remote sensing techniques have allowed the mapping and studying of lava flows in unprecedented detail. A composite GIS technique is introduced to obtain high resolution boundaries of lava flow fields. This technique is mainly based on the processing of LIDAR-derived maps and digital elevation models (DEMs). The probabilistic code DOWNFLOW is then used to simulate eight large flow fields formed at Mount Etna in the last 25 years. Thanks to the collection of 6 DEMs representing Mount Etna at different times from 1986 to 2007, simulated outputs are obtained by running the DOWNFLOW code over pre-emplacement topographies. Simulation outputs are compared with the boundaries of the actual flow fields obtained here or derived from the existing literature. Although the selected fields formed in accordance with different emplacement mechanisms, flowed on different zones of the volcano over different topographies and were fed by different lava supplies of different durations, DOWNFLOW yields results close to the actual flow fields in all the cases considered. This outcome is noteworthy because DOWNFLOW has been applied by adopting a default calibration, without any specific tuning for the new cases considered here. This extensive testing proves that, if the pre-emplacement topography is available, DOWNFLOW yields a realistic simulation of a future lava flow based solely on a knowledge of the vent position. In comparison with deterministic codes, which require accurate knowledge of a large number of input parameters, DOWNFLOW turns out to be simple, fast and undemanding, proving to be ideal for systematic hazard and risk analyses.

Detecting short-term evolution of Etnean scoria cones: a LIDAR-based approach

by Simone Tarquini

Fornaciai A., Behncke B., Favalli M., Neri M., Tarquini S., Boschi E
2010, Bulletin of Volcanology 72, 1209-1222.

The 2001 and 2002–2003 flank eruptions on Mount Etna (Italy) were characterized by intense explosive activity which... more The 2001 and 2002–2003 flank eruptions on Mount Etna (Italy) were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones (one from each eruption) on the upper southern flank of the volcano. Continuous monitoring of Etna, especially during flank eruptions, has provided detailed information on the growth of these cones. They differ in genesis, shape, and size. A set of high resolution (1 m) digital elevation models (DEMs) derived from light detection and ranging (LIDAR) data collected during four different surveys (2004, 2005, 2006, and 2007) has been used to map morphology and to extract the morphometric parameters of the scoria cones. By comparing LIDAR-derived DEMs with a pre-eruption (1998) 10 m DEM, the volume of the two scoria cones was calculated for the first time. Comparison of the LIDAR-derived DEMs revealed in
unprecedented detail morphological changes during scoria
cone degradation. In particular, the morphologically more exposed and structurally weaker 2002–2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion.

The changing face of Mount Etna's summit area documented with Lidar technology

by Simone Tarquini

Neri M., Mazzarini F., Tarquini S., Bisson M., Isola I., Behncke B., Pareschi M. T.
2008, Geophysical Research Letters 35, L09305.

Morphostructural data derived from Lidar (Light detection and ranging) surveys carried out on Mount Etna in 2005 and... more Morphostructural data derived from Lidar (Light detection and ranging) surveys carried out on Mount Etna in 2005 and 2007 are compared with earlier aerophotogrammetric surveys in 1986 and 1998. These data render an unprecedentedly clear and quantitative image of morphostructural and volumetric changes that have affected the summit area of the volcano in the past two decades and permit the production of a new topographic map. The computed volume gain during the 1986–2007 period amounts to 112 ± 12 x 106 m3, at a mean annual rate of ca. 5.3 x 106 m3. The comparison of the various surveys furthermore emphasizes the levels of accuracy and resolution of the different techniques applied. The Lidar technology used in 2007 allows production of high-precision maps in near-real-time, facilitating work concerning environmental hazards such as numerical simulations of, e.g., lava flows.

Anatomy of the Dead Sea Transform from lithospheric to microscopic scale

by Nils Maercklin

M. Weber et al. (2009). Reviews of Geophysics, 47, RG2002, doi:10.1029/2008RG000264

Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated.... more Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (~20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the micrometer to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.

Floods in Greece, a statistical and spatial approach

by Michalis Diakakis

Earth observation data and GIS techniques for earthquake risk assessment in western Gulf of Corinth (Greece)

by Emmanuel Vassilakis

PARCHARIDIS IS., METAXAS C. & VASSILAKIS EMM.

This study attempts to demonstrate the utility of differential SAR interferometry and very high resolution satellite... more This study attempts to demonstrate the utility of differential SAR interferometry and very high resolution satellite optical data for the assessment of earthquake risk, using GIS, in the western part of the Gulf of Corinth, a seismically active region of Greece, which suffered the effects of the Eigion earthquake (M=6.1) of June 1995. During the project, both archive and newly acquired ERS data have been used to generate conventional differential interferograms and produce a deformation map over the area. An IKONOS-2 image was used to create and update information concerning urban structure like building blocks, road network, facilities etc. A first attempt to evaluate EO contribution in the earthquake risk assessment system shows that the DInSAR is suitable only for co-seismic deformation monitoring and very high resolution data exhibit high performance in urban structures mapping.

Evaluation of the GLC2000 and NALC2005 land cover products for LAI retrieval over Canada

by Alemu Gonsamo

Alemu Gonsamo and Jing M. Chen. 2011. Evaluation of the GLC2000 and NALC2005 land cover products for LAI retrieval over Canada. Canadian Journal of Remote Sensing. Vol. 37, No. 3, pp. 302313

Monitoring Shorebird Habitat using Photogrammetry: The case of Western Snowy Plover at Coal Oil Point Reserve, Santa Barbara, California

by Michele M. Tobias

Published in 'Physical Geography', 2008

The goal of this study was to determine how digital photogrammetry can be used to describe and monitor shorebird... more The goal of this study was to determine how digital photogrammetry can be used to describe and monitor shorebird habitat. Methods previously used for monitoring beach erosion were applied to shorebird habitat, concentrating on the requirements of Western Snowy Plovers. How the physical habitat of Western Snowy Plovers has changed over time was investigated at Sand Beach, which is part of Coal Oil Point Reserve in Santa Barbara, California, from 1928 to 2004, using width, area, and elevation data gathered from a series of aerial photographs. Single georeferenced photographs were used to measure width at regular intervals and area for each year a photo was available. Georeferenced aerial photographs can be used to obtain accurate measurements of beach area and width. Orthorectification is not necessary if photos can be georeferenced with minimal error. Sands Beach was found to be increasing in area. This was due mainly to the retreat of the vegetation line as the mouth of Devereux Slough shifted in 1992 rather than an accumulation of sand on the beach.

Roberts, N., Cunningham, D., 2008. Automated alluvial fan discrimination, Quaternary fault identification, and the distribution of tectonically reactivated crust in the Gobi Altai region, southern Mongolia. International Journal of Remote Sensing 29.

by Nick Roberts

published in 'International Journal of Remote Sensing'

In this study, we demonstrate the utility of SRTM topographic data as a tool for mapping alluvial fans and documenting... more In this study, we demonstrate the utility of SRTM topographic data as a tool for mapping alluvial fans and documenting the distribution of tectonically reactivated crust in the Gobi Altai region of southern Mongolia. The topographic data clearly reveal three diagnostic indicators of crustal reactivation: visible fault scarps, sharply defined faulted mountain fronts, and alluvial fan complexes adjacent to steep mountain fronts. These three variables are combined to produce a new surface tectonic activity map of the region. By selecting terrain with slope thresholds between 1 and 8° and then applying a topographic roughness filter, alluvial fan complexes are automatically discriminated and mapped throughout the region for the first time. This allows clear identification of Quaternary uplifted regions (and associated thrust faults) and the distribution of clastic basins which have experienced a two‐stage history: Mesozoic rifting and Late Cenozoic alluvial sedimentation. By analysing mountain front sinuosity and alluvial fan topographic roughness, the tectonic activity of individual mountain fronts is quantitatively compared and ranked. Most ranges are upthrust fault blocks with outward directed thrusts and bajadas bounding their N‐NE and S‐SW fronts. The spatial distribution of youthful mountain ranges, flanking fan complexes, and Quaternary thrust and strike‐slip faults is consistent with ongoing sinistral transpressional crustal reactivation throughout the region.

Global Optimization versus Deterministic Pruning for the Classification of Remotely Sensed Imagery

by Dimitris Stathakis

Using a genetic algorithm to find optimal neural network structure for classification problems.

The effect of pruning neural network structures in remote
sensing is investigated. Standard pruning methods,... more The effect of pruning neural network structures in remote
sensing is investigated. Standard pruning methods, i.e.,
Optimal Brain Damage and Optimal Brain Surgeon, are
compared with pruning based on a genetic algorithm. Direct
coding is used to represent the links of the network for
optimization with a canonical genetic algorithm using binary
representation. The results show that the genetic algorithm
is the only method able to discover a significantly better
neural network structure. The main drawback of the genetic
approach is the extensive training time required.

Applying ASTER thermal infrared spectral indices for geological mapping on the Tibetan Plateau

by Robert Corrie

Corrie, R.K., Ninomiya, Y., and Aitchison, J.C.
ISPRS Technical Commission VIII Symposium, WG5: Energy and Solid Earth
Kyoto, Japan, August 9 - 12, 2010

The Tibetan Plateau holds clues to understanding the dynamics and mechanisms associated with continental growth. Part... more The Tibetan Plateau holds clues to understanding the dynamics and mechanisms associated with continental growth. Part of the region is characterized by zones of ophiolitic mélange believed to represent the remnants of ancient oceanic crust and underlying upper mantle emplaced during oceanic closures. However, due to the remoteness of the region and the inhospitable terrain many areas have not received detailed investigation. Increased spatial and spectral resolution of satellite sensors have made it possible to map in greater detail the mineralogy and lithology than in the past. Recent work by Yoshiki Ninomiya of the Geological Survey of Japan has pioneered the use of several spectral indices for the mapping of quartzose, carbonate, and silicate rocks using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) thermal infrared (TIR) data. In this study, ASTER TIR indices have been applied to a region in western-central Tibet for the purposes of assessing their effectiveness for differentiating ophiolites and other lithologies. The results agree well with existing geological maps and other published data. The study area was chosen due to its diverse range of rock types, including an ophiolitic mélange, associated with the Bangong-Nujiang suture (BNS) that crops out on the northern shores of Lagkor Tso and Dong Tso („Tso‟ is Tibetan for lake). The techniques highlighted in this paper could be applied to other geographical regions where similar geological questions need to be resolved. The results of this study aim to show the utility of ASTER TIR imagery for geological mapping in semi-arid and sparsely vegetated areas on the Tibetan Plateau.

Applying Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) spectral indices for geological mapping and mineral identification on the Tibetan Plateau

by Robert Corrie

Corrie, R.K., Ninomiya, Y., and Aitchison, J.C., 2010

The Tibetan Plateau holds clues to understanding the dynamics and mechanisms associated with continental growth. Part... more The Tibetan Plateau holds clues to understanding the dynamics and mechanisms associated with continental growth. Part of the region is characterized by zones of ophiolitic mélange believed to represent the remnants of ancient oceanic crust and underlying upper mantle emplaced during oceanic closures. However,  due to the remoteness of the region and the inhospitable terrain many areas have not received detailed investigation.  Increased spatial and spectral resolution of satellite sensors have made it possible to map in greater detail the mineralogy and lithology than in the past. Recent work by Yoshiki Ninomiya of the Geological Survey of Japan has pioneered the use of several spectral indices for the mapping of quartzose, carbonate, and silicate rocks using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) thermal infrared (TIR) data. In this study, ASTER TIR indices have been applied to a region in western-­central Tibet for the purposes of assessing their effectiveness for differentiating ophiolites and other lithologies. The results agree well with existing geological maps and other published data. The study area was chosen due to its diverse range of rock types, including an ophiolitic mélange, associated with the Bangong-­Nujiang suture (BNS) that crops out on the northern shores of Lagkor Tso and Dong Tso ('Tso' is Tibetan for lake). The techniques highlighted in this paper could be applied to other geographical regions where similar geological questions need to be resolved. The results of this study aim to show the utility of ASTER TIR imagery for geological mapping in semi-­arid and sparsely vegetated areas on the Tibetan Plateau.

A Marine Radar Wind Sensor

by Heiko Dankert

Journal of Atmospheric and Oceanic Technology, 1629–1642, 2007; Heiko Dankert and Jochen Horstmann

A new method for retrieving the wind vector from radar-image sequences is presented. This method, called WiRAR, uses a... more A new method for retrieving the wind vector from radar-image sequences is presented. This method, called WiRAR, uses a marine X-band radar to analyze the backscatter of the ocean surface in space and time with respect to surface winds. Wind direction is found using wind-induced streaks, which are very well aligned with the mean surface wind direction and have a typical spacing above 50 m. Wind speeds are derived using a neural network by parameterizing the relationship between the wind vector and the normalized radar cross section (NRCS). To improve performance, it is also considered how the NRCS depends on sea state and atmospheric parameters such as air–sea temperature and humidity. Since the signal-to-noise ratio in the radar sequences is directly related to the significant wave height, this ratio is used to obtain sea state parameters. All radar datasets were acquired in the German Bight of the North Sea from the research platform FINO-I, which provides environmental data such as wind measurements at different heights, sea state, air–sea temperatures, humidity, and other meteorological and oceanographic parameters. The radar-image sequences were recorded by a marine X-band radar installed aboard FINO-I, which operates at grazing incidence and horizontal polarization in transmit and receive. For validation WiRAR is applied to the radar data and compared to the in situ wind measurements from FINO-I. The comparison of wind directions resulted in a correlation coefficient of 0.99 with a standard deviation of 12.8°, and that of wind speeds resulted in a correlation coefficient of 0.99 with a standard deviation of 0.41 m s−1. In contrast to traditional offshore wind sensors, the retrieval of the wind vector from the NRCS of the ocean surface makes the system independent of the sensors’ motion and installation height as well as the effects due to platform-induced turbulence.

Analyzing the influence of upslope bedrock outcrops on shallow landsliding

by Paolo Tarolli

Published in Geomorphology, 2008. Co-authored with Marco Borga and Giancarlo Dalla Fontana

A model for the prediction of topographic and climatic control on shallow landsliding in mountainous terrain is... more A model for the prediction of topographic and climatic control on shallow landsliding in mountainous terrain is enhanced to analyse the impact of upslope rocky outcrops on downslope shallow landsliding. The model uses a ‘generalised quasi-dynamic wetness index’ to describe runoff propagation on bare rock surfaces connected to downslope soil-mantled topographic elements. This approach yields a simple enhanced model capable of describing the influence of upslope bedrock outcrops on the pattern of downslope soil saturation. The model is applied in both diagnostic and predictive modes to a small catchment in the eastern Italian Alps for which a detailed inventory of shallow landslides in areas dominated by rocky outcrops is available. In the diagnostic mode, the model is used with satisfactory results to reproduce the pattern of instability generated by an intense short-duration storm occurred on 14 September 1994, which triggered a large percentage of the surveyed landslides. In the predictive mode, the model is used for hazard assessment, and the return time of the critical rainfall needed to cause instability for each topographic element is determined. Modelling results obtained in the predictive mode are evaluated against all the surveyed landslides. It is revealed that the generalised quasi-dynamic model offers considerable improvement over the non-generalised quasi-dynamic model and the steady-state model in predicting existing landslides as represented in the considered landslide inventory.

Innesco di frane superficiali durante eventi di precipitazione brevi ed intensi in zone alpine

by Paolo Tarolli

Published in Quaderni di Idronomia Montana (26), 2006. Co-authored with Marco Borga, Bernardo Cesare, Francesco Zanon, Mauro Tollardo, Pierpaolo Maccon

L’analisi empirica degli eventi di frana e colata detritica ha evidenziato l’importanza del deflusso generato in... more L’analisi empirica degli eventi di frana e colata detritica ha evidenziato l’importanza del deflusso generato in corrispondenza di superfici semiimpermeabili, quali possono essere considerati gli affioramenti rocciosi, sull’innesco di fenomeni di instabilità superficiale delle coltri di suolo dei versanti a valle. La memoria descrive un modello inteso a rappresentare i processi idrologici e geomeccanici che controllano la stabilità dei versanti in tali situazioni. Il modello viene combinato con osservazioni radar di pioggia e consente di determinare un indice, denominato ‘Storm shallow landsliding potential index – SSLIP’, che permette di evidenziare il potenziale di innesco di frana per un evento meteorologico assegnato. Il modello e l’indice così definito sono stati applicati per lo studio dei collassi di versante innescati da due eventi di precipitazione intensa verificatisi in Alto Adige (Valle Aurina) durante l’estate 2005. I risultati conseguiti hanno evidenziato la buona capacità predittiva della metodologia proposta.

A New Method for Determination of Most Likely Landslide Initiation Points and the Evaluation of Digital Terrain Model Scale in Terrain Stability Mapping

by Paolo Tarolli

Published in HESS, 2006. Co-authored with D.G. Tarboton

This paper introduces a new approach for determining the most likely initiation points for landslides from potential... more This paper introduces a new approach for determining the most likely initiation points for landslides from potential instability mapped using a terrain stability model. This approach identifies the location with critical stability index from a terrain stability model on each downslope path from ridge to valley. Any measure of terrain stability may be used with this approach, which here is illustrated using results from SINMAP, and from simply taking slope as an index of potential instability. The relative density of most likely landslide initiation points within and outside mapped landslide scars provides a way to evaluate the effectiveness of a terrain stability measure, even when mapped landslide scars include run out zones, rather than just initiation locations. This relative density was used to evaluate the utility of high resolution terrain data derived from airborne laser altimetry (LIDAR) for a small basin located in the Northeastern Region of Italy. Digital Terrain Models were derived from the LIDAR data for a range of grid cell sizes (from 2 to 50 m). We found appreciable differences between the density of most likely landslide initiation points within and outside mapped landslides with ratios as large as three or more with the highest ratios for a digital terrain model grid cell size of 10 m. This leads to two conclusions: (1) The relative density from a most likely landslide initiation point approach is useful for quantifying the effectiveness of a terrain stability map when mapped landslides do not or can not differentiate between initiation, runout, and depositional areas; and (2) in this study area, where landslides occurred in complexes that were sometimes more than 100 m wide, a digital terrain model scale of 10 m is optimal. Digital terrain model scales larger than 10 m result in loss of resolution that degrades the results, while for digital terrain model scales smaller than 10 m the physical processes responsible for triggering landslides are obscured by smaller scale terrain variability

The effectiveness of airborne LiDAR data in the recognition of channel bed morphology

by Paolo Tarolli

Published in Catena, 2008. Co-authored with Marco Cavalli, Lorenzo Marchi and Giancarlo Dalla Fontana

High-resolution topographic data have the potential to differentiate the main morphological features of a landscape.... more High-resolution topographic data have the potential to differentiate the main morphological features of a landscape. This paper analyses the capability of airborne LiDAR-derived data in the recognition of channel-bed morphology. For the purpose of this study, 0.5 m and 1 m resolution Digital Terrain Models (DTMs) were derived from the last pulse LiDAR data obtained by filtering the vegetation points. The analysis was carried out both at 1-D scale, i.e. along the longitudinal channel profile, and at 2-D scale, taking into account the whole extent of the channel bed. The 1-D approach analyzed the residuals of elevations orthogonal to the regression line drawn along the channel profile and the standard deviation of local slope. The 2-D analysis was based on two roughness indexes, consisting on the local variability of the elevation and slope of the channel bed. The study was conducted in a headwater catchment located in the Eastern Italian Alps. The results suggested a good capability of LiDAR data in the recognition of river morphology giving the potential to distinguish the riffle-pool and step-pool reaches.

Analysis of the headwater basins’ morphology by high resolution LiDAR-derived DTM

by Paolo Tarolli

Published in International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, 2008. Co-authored with Giancarlo Dalla Fontana

High resolution topographic data have the potential to differentiate the main morphological features of a landscape.... more High resolution topographic data have the potential to differentiate the main morphological features of a landscape. For the purpose of this study the Digital Terrain Models (DTMs) ranging between 1m and 20m (cell size) were derived from the last pulse LiDAR data by filtering the vegetation points. We tested the effects of different resolutions in the analysis of river morphology, and potential slope stability. The study was conducted in two headwater catchments located in the eastern Italian Alps where a high-quality set of LiDAR data was available. The results indicated for higher DTM resolutions an improved effectiveness in the recognition of river morphology. Otherwise the progressive finer DTM resolution does not necessarily improve the interpretation of slope stability processes especially if landslides occur at a spatial scale significantly greater than cell size.

Hillslope-to-valley transition morphology: new opportunities from high resolution DTMs

by Paolo Tarolli

Published in Geomorphology, 2009. Co-authored with Giancarlo Dalla Fontana

The search for the optimal spatial scale for observing landforms to understand physical processes is a fundamental... more The search for the optimal spatial scale for observing landforms to understand physical processes is a fundamental issue in geomorphology. Topographic attributes derived from Digital Terrain Models (DTMs) such as slope, curvature and drainage area provide a basis for topographic analyses. The slope–area relationship has been used to distinguish diffusive (hillslope) from linear (valley) processes, and to infer dominant sediment transport processes. In addition, curvature is also useful in distinguishing the dominant landform process. Recent topographic survey techniques such as LiDAR have permitted detailed topographic analysis by providing high-quality DTMs. This study uses LiDAR-derived DTMs with a spatial scale between 1 and 30 m in order to find the optimal scale for observation of dominant landform processes in a headwater basin in the eastern Italian Alps where shallow landsliding and debris flows are dominant. The analysis considered the scaling regimes of local slope versus drainage area, the spatial distribution of curvature, and field observations of channel head locations. The results indicate that: i) hillslope-to-valley transitions in slope–area diagrams become clearer as the DTM grid size decreases due to the better representation of hillslope morphology, and the topographic signature of valley incision by debris flows and landslides is also best displayed with finer DTMs; ii) regarding the channel head distribution in the slope–area diagrams, the scaling regimes of local slope versus drainage area obtained with grid sizes of 1, 3, and 5 m are more consistent with field data; and iii) the use of thresholds of standard deviation of curvature, particularly at the finest grid size, were proven as a useful and objective methodology for recognizing hollows and related channel heads.