Geomorphological Hazards

lterations in river morphological quality are derived from quantification of human pressures as well as river morphological alteration. Taleghan River is an important source of water for the irrigation of Agri cultural lands in Qazvin Plain. For some economic considerations of Taleghan dam reservoir on the river as well as geology, some reaches of the river have undergone alterations. It seems important to morphological quality assessment in order to planning issues. Our study’s aim is to contribute to the morphological quality evaluation based on a revisited Morphological Quality Index (rMQI) protocol. The rMQI scoring system allows for the quantification of changes when compared to reference conditions. The rMQI corresponds to less than 30%, reflecting a good morphological quality; the rMQI corresponds to more than 30%, reflecting an extremely poor morphological quality. In this context, the paper presents all of the Taleghan River reaches suffer from an extremely poor morphological quality. Causes of degradation are meandering as well as numerous anthropogenic pressures in the upstream part of the basin. In order to revive Taleghan River as well as improve its water quality, preserving and remediating native vegetation, prevention and remediation of land use degradation in upstream's basin as well as river bank erosion control measures can use hard and soft strategies engineering are recommended.

La cuenca alta del río General se localiza en el centro-sur de Costa Rica, a 80 km al SE de San José. Esta región está sujeta a una declaratoria oficial por parte de la Comisión Nacional de Prevención de Riesgos y Atención de Emergencias como área de amenaza potencial de inundaciones y procesos de ladera, sin que existan estudios claros que demuestren su peligrosidad en toda su extensión. Esto conlleva a la afectación directa del desarrollo socioeconómico del territorio y a un aumento de la vulnerabilidad, que se incrementa por la existencia de un crecimiento urbano informal (ilegal). Si bien no es posible regular la ocupación de terrenos no aptos para la vivienda, un estudio de peligros geomorfológicos permite zonificar el grado de amenaza a inundaciones y procesos de ladera, y de esta manera los habitantes serían menos vulnerables, podrían evitarse pérdidas humanas y acortar los tiempos de recuperación social.

La dinámica de este territorio se ve influenciada por eventos de intensas lluvias estacionales, el impacto indirecto de ciclones tropicales y la sismicidad que disparan procesos de ladera e inundaciones, como fueron los casos de los huracanes Kittie en 1955, Joan en 1988, César en 1996 y la tormenta tropical Alma en 2008; así como el terremoto de Buenavista en 1983. Lo anterior justifica la elaboración de un mapa de peligros a inundaciones y procesos de ladera en la cuenca alta del río General, bajo un criterio geomorfológico. Para su construcción fue necesario realizar una serie de mapas morfométricos y uno morfogenético, cartografías que se sobreponen para establecer las zonas con diferente grado de peligro.

Los criterios utilizados para la elaboración de la cartografía morfométrica y geomorfológica detallada de la cuenca alta del río General fueron los de Bashenina (1977) y Simonov (1985) los cuales están basados en una clasificación genética del relieve (endógeno, endógeno modelado y exógeno). Este método se podría clasificar como la Escuela Mexicana, la cual combina aspectos de la Geomorfología Francesa y Rusa. Dicha metodología es la primera vez que se desarrolla en Costa Rica y será utilizada en otras regiones del país para el conocimiento científico así como la solución de problemas tanto en la prevención de desastres como el ordenamiento territorial.

El trabajo se compone por seis capítulos. Capítulo I: Peligros geomorfológicos: marco conceptual, Capítulo II: Características Físico-Geográficas, Capítulo III: Tectónica y geología, Capítulo IV: Morfometría, Capítulo V: Geomorfología, y Capítulo VI: Peligros geomorfológicos.

Los abanicos aluviales morfodinámicamente activos que han sido construidos por depósitos torrenciales, representan áreas altamente inestables, cuyas condiciones definen escenarios de amenaza para las poblaciones asentadas sobre ellos. Se consideró analizar los parámetros físicos y morfométricos de las cuencas de la vertiente norte de “El Ávila”, como controles sobre el desarrollo y la morfología de sus abanicos. La metodología comprendió: (a) caracterización de la morfología de los abanicos; (b) mediciones de la morfometría de las cuencas y de los abanicos; (c) construcción de perfiles de cauces principales sobre los abanicos, y perfiles topográficos de éstos; (e) estimación de las superficies de afloramientos litológicos en las cuencas; y (f) correlación entre parámetros morfométricos de los abanicos y de las cuencas. Los abanicos exhiben morfologías del tipo retrollenado desde el frente montañoso, con coalescencia en algunos sectores, y solapamiento en el caso del abanico Quebrada Seca sobre el abanico Punta El Caribe. Sus perfiles longitudinales y transversales muestran las típicas formas cóncava y convexa respectivamente, con ligeras variaciones en sus trazos. Se comportan de igual forma como abanicos-deltas, dado que parte de sus extensiones (depósitos) se encuentran bajo las aguas marinas. Son abanicos de pequeñas dimensiones (áreas entre 0,79 Km2 y 5,71 Km2) y pendientes longitudinales entre 1,67 % y 9,10 %. La litología predominante en cada cuenca, ejerce gran influencia en la morfología, desarrollo y extensión de su abanico. Los parámetros morfométricos de los abanicos de mejores correlaciones con los de las cuencas, son el área y la pendiente de atrincheramiento.

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

"Horcones Inferior glacier’s moraines extend for about 20 km, and we can distinguish five different areas, beginning with the most recent ones: 1) The current moraines, which correspond to lateral moraines and one frontal moraine. 2) The Confluência moraines, which form a rather complex structure, and which appear to include a medial moraine, a hummock moraine and several moraines coming from neighboring valleys. 3) The Horcones moraines, which appear to constitute two distinct sets. 4) The Penitentes moraines, between Puente del Inca and Punta de Vacas. 5) The Punta de Vacas moraine, which runs downstream Punta de Vacas, in the proglacial area, and may result from the glacier’s progress, coming from Horcones and meeting other Andean glaciers, probably being the biggest and oldest glacier’s
advance in the valley. In this paper, we will study the first three of the mentioned areas.
Keywords: Argentinean Andes, Moraines, Glacial Geomorphology, Geoheritage, Geomorphologic hazards"

The next generation of digital elevation data (≤3 m resolution) calls for the development of new algorithms for the objective extraction of geomorphic features, such as channel networks, channel heads, bank geometry, landslide scars, and service roads. In this work, we test the performance of two newly developed algorithms for the extraction of geomorphic features: the wavelet-based extraction methodology developed

The next generation of digital elevation data (≤ 3m resolution)
calls for the development of new algorithms for the objective extraction of geomorphic features, such as channel networks, channel heads, bank geometry, landslide scars, service roads, etc. In this work, we test the performance of two newly developed algorithms for the extraction of geomorphic
features: the wavelet-based extraction methodology developed by Lashermes et al. [2007] and the GeoNet-nonlinear diffusion and geodesic pathsmethodology proposed by Passalacqua et al. [2010]. The study area is part of the Rio Cordon basin, a headwater alpine catchment located in the Dolomites, a mountainous region in the Eastern Italian Alps. The aim of this work is to compare the capability of the two new algorithms in extracting the channel network, capturing channel heads, relevant channel disruptions corresponding to landslides, and representative channel cross-sections. The extracted
channel networks are also compared to the ones obtained using classical methodologies based on an area threshold and an area-slope threshold. A high resolution Digital Terrain Model (DTM) of 1 m served as the basis for such analysis. The results suggest that, although the wavelet-based methodology performs well in the channel network extraction and is able to detect channel heads and channel disruptions, the local nonlinear filter together with the global geodesic optimization used in GeoNet is more robust and computationally efficient, while achieving better localization and extraction of features,
especially in areas where gentle slopes prevail. We conclude that these new methodologies should be considered as valid alternatives to classical methodologies for channel network extraction from lidar, in addition to offering the potential for calibration-free channel source identification and also extraction of additional features of interest.

In recent years, new remote-sensed technologies, such as airborne and terrestrial laser scanner, have improved the detail and the quality of topographic information, providing topographical high-resolution and high-quality data over larger areas better than other technologies. A new generation of high-resolution (<3 m) digital terrain models (DTMs) is now available for different areas and is widely used by researchers, offering new opportunities for the scientific community. These data call for the development of a new generation of methodologies for an objective extraction of geomorphic features, such as channel heads, channel networks, bank geometry, debris-flow channel, debris-flow deposits, scree slope, landslide and erosion scars, etc. A high-resolution DTM is able to detect the divergence/convergence of areas related to unchannelized/channelized processes with better detail than a coarse DTM. In this work, we tested the performance of new methodologies for an objective extraction of geomorphic features related to shallow landsliding processes (landslide crowns), and bank erosion in a complex mountainous terrain. Giving a procedure that automatically recognizes these geomorphic features can offer a strategic tool to map natural hazard and to ease the planning and the assessment of alpine regions. The methodologies proposed are based on the detection of thresholds derived by the statistical analysis of variability of landform curvature. The study was conducted on an area located in the Eastern Italian Alps, where an accurate field survey on shallow landsliding, erosive channelized processes, and a high-quality set of both terrestrial and airborne laser scanner elevation data is available. The analysis was conducted using a high-resolution DTM and different smoothing factors for landform curvature calculation in order to test the most suitable scale of curvature calculation for the recognition of the selected features. The results revealed that (1) curvature calculation is strongly scaledependent, and an appropriate scale for derivation of the local geometry has to be selected according to the scale of the features to be detected; (2) such approach is useful to automatically detect and highlight the location of shallow slope failures and bank erosion, and it can assist the interpreter/operator to correctly recognize and delineate such phenomena. These results highlight opportunities but also challenges in fully automated methodologies for geomorphic feature extraction and recognition.

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.

Os territórios urbanos acompanham os novos paradigmas de desenvolvimento e mudança no contexto de desígnios que pretendem promover territórios mais coesos, competitivos, atrativos e com valor económico e cultural. A requalificação urbana, como instrumento incontornável da sustentabilidade urbana e processo estratégico, envolve a articulação e integração de diversas componentes, reflete a tendência para a reutilização de infraestruturas e equipamentos existentes, e constitui uma oportunidade para salvaguardar e valorizar o património. Esta matriz teórica será aprofundada através de um estudo de caso (a cidade de Leiria) relacionado com a implementação do Programa Polis, no sentido de analisar os efeitos ao nível da organização espacial, da salvaguarda e valorização do património, e da perceção e vínculos por parte dos cidadãos que vivem e utilizam os territórios intervencionados.

Erg of Gavkhooni Playa is one of the important geomorphologic landforms of Quaternary period in Iran. The area is located on the western part of Gaovkhoni Playa and 140 km to the Southeast of Isfahan, Iran. This study presents a display of landform of Erg and the area has been divided into three parts (NorthCentral and South). The objective of this study is to identify geomorphologic facieses by GIS t and RS. The research method is a processing technique such as basis analyzing, a composite of panchromatic band with multi-spectral band, to examine line spectral curved, to examine optimum composites using an enhancement method such as filtering and contrast. As a result, to display sand landforms and geomorphologic facieses such as Barkhan, Safe, Star hill, playa’s facieses, Skirt and Delta, Sand Zone and the sediment between the hills and geomorphologic landform map are based on Erg of Gavkhoni Playa and geomorphologic facieses of the area. 

Keywords:
Erg Govkhooni Playa, Erg morphology, land sat images, geomorphologic map.

Erg of Gavkhooni Playa is one of the important geomorphologic landforms of Quaternary period in Iran. The area is located on the western part of Gaovkhoni Playa and 140 km to the Southeast of Isfahan, Iran. This study presents a display of landform of Erg and the area has been divided into three parts (North-Central and South). The objective of this study is to identify geomorphologic facieses by GIS t and RS. The research method is a processing technique such as basis analyzing, a composite of panchromatic band with multi-spectral band, to examine line spectral curved, to examine optimum composites using an enhancement method such as filtering and contrast. As a result, to display sand landforms and geomorphologic facieses such as Barkhan, Safe, Star hill, playa’s facieses, Skirt and Delta, Sand Zone and the sediment between the hills and geomorphologic landform map are based on Erg of Gavkhoni Playa and geomorphologic facieses of the area.

This special issue brings together studies on the innovative use of remotely sensed DTMs for Earth science applications for obtaining new understanding of earth surface processes. The idea for this issue arose from a session on “Remotely sensed DTM for Hydrogeomorphic Applications” convened the proponents as well as William E. Dietrich and Salvatore Grimaldi, during the 2007 Annual Fall Meeting of the American Geophysical Union, held in San Francisco, California. The three oral and one poster sessions attracted 41 abstracts from North America, Europe and Asia, providing an opportunity to review methods, discuss challenges, and evaluate recent technological advances in the use of remotely sensed topographic data for Earth surface processes. Some of the posters and presentations discussed during the meeting sessions were developed into the papers appearing in this special issue. Our goal is to share advances in landscape analysis that are significantly improved by the use of different...

Resumo:
Após algumas considerações sobre riscos naturais na área de Coimbra, pretende-se explorar as potencialidades dos Sistemas de Informação Geográfica (SIG’s) para modelizar e cartografar o risco de movimentos de materiais em vertentes numa pequena área a Sul da cidade.

Résumé:
Après quelques considérations autour des risques naturels dans la région Coimbra, nous projetons d'explorer les potentialités des Systèmes d’Information Géographique( SIG’s) afin de modeler et de cartographier les mouvements de versant dans une petite région au sud de la ville.

Abstract:
After some considerations about natural risks in the Coimbra area, we intend to explore the Geographic Information System (GIS) potentialities for modelling and mapping slope movements
at a small south area of the town.