Analysis Of Aerial Photographs Research Articles

Morphodynamic evolution and stratal architecture of translating tidal point bars: Inferences from the northern Venice Lagoon (Italy)

AbstractThe widespread distribution of tidal creeks and channels that undertake meandering behaviour in modern coasts contrasts with their limited documentation in the fossil record, where point‐bar elements arising from the interaction between a mix of both fluvial and tidal currents are mainly documented. The sedimentary products of tidal channel‐bend evolution are relatively poorly known, and few studies have focused previously on specific facies models for tidal point bars present in modern settings. This study improves understanding of tidal channel meander bends through a multi‐disciplinary approach that combines analyses of historical aerial photographs, measurements of in‐channel flow velocity, high‐resolution facies analyses of sedimentary cores and three‐dimensional architectural modelling. The studied channel bend (12 to 15 m wide and 2 to 3 m deep) drains a salt marsh area located in the north‐eastern sector of the microtidal Venice Lagoon, Italy. Historical photographs show that, during the past 77 years, the bend has translated seaward ca 15 m. Results show that the channel bend formed on a non‐vegetated mud flat that was progressively colonized by vegetation. Seaward translation occurred under aggradational conditions, with an overall migration rate of 0·2 to 0·3 m year−1, and was promoted by the occurrence of cohesive, poorly erodible outer bank deposits. Ebb currents are dominant, and translation of the channel bend promotes erosion and deposition along the landward and seaward side of the bar, respectively. Tidal currents show a clear asymmetry in terms of velocity distribution, and their offset pattern provides a peculiar grain‐size distribution within the bar. During the flood stage, sand sedimentation occurs in the upper part of the bar, where the maximum flow velocity occurs. During the ebb stage, the bar experiences the secondary helical flow that accumulates sand at the toe of the bar. Lateral stacking of flood and ebb deposits has caused the formation of localized coarsening‐upward and fining‐upward sedimentary packages, respectively.

Geomorphology of Talacasto alluvial fan, Precordillera of San Juan, Argentina

ABSTRACTWe present a 1:50,000 geomorphological map of the Talacasto river alluvial fan (93 km2), located in the Central Andean Precordillera of Argentina. The aim of this map is to identify and classify dynamic and potentially destructive geomorphological processes such as gully erosion, headward erosion, concentrated erosion, laminar erosion and similar features that are present in an alluvial fan, so as to identify unstable sectors for public infrastructure. This map is the result of combining remote sensing data, aerial photographs analysis and fieldwork. Landforms and active geomorphological processes are identified, classified and illustrated for this Quaternary alluvial fan. Four Quaternary landscape subunits were classified, taking into account morphogenetic characteristics and erosional processes such as: (1) Exhumed and erosional landforms inducted by neotectonic activity; (2) Alluvial landforms; (3) Polygenetic landforms covered in glacis; and (4) Playa lake landforms. The presence of desert pavements and salt-hardened subsoil formations contributes to the generation and transmission of surface runoff during summer heavy rains, causing alluvial hazards and damages in routes and roads.

The success of recent land management efforts to reduce soil erosion in northern France

Soil erosion is an important problem in open-field agricultural landscapes. With almost no permanent vegetation in small headwater catchments, and with few physical obstacles to reduce runoff velocities, runoff concentration along linear landscape elements (plot boundaries) or thalwegs frequently causes ephemeral gullies to form — the latter reflecting the poor hydrogeomorphic condition of the land- and soilscape. To address this problem, and to remediate negative on- and off-site effects, land management efforts have multiplied over the past decades in many regions. This includes, amongst other measures, the implementation of vegetation barriers called ‘fascines’. In the loess-dominated Aa River basin of northern France, where cropland accounts for 67% of the cover, we investigated the effect of fascines on ephemeral gully erosion dynamics, together with rainfall characteristics and cropland management. This was accomplished through a spatially explicit study of 269 sites prone to ephemeral gullying using a diachronic analysis of historical aerial photographs. Between 1947 and 2012, ephemeral gully densities at the scale of the Aa River basin (643km2) varied between 0.39 and 1.31mha−1 (long-term average of 0.68mha−1 (with local maxima up to 9.35mha−1). Densities are, however, much higher when only considering the most erosion-vulnerable municipalities (long-term average of 2.23–4.30mha−1); those values should be used when comparing results from this study to other reports of ephemeral gully erosion. Fascines were introduced in 2001 and were present in ~30% of the gully erosion sites by 2012. Although the presence of fascines has an effect on gully length reduction, spatial and temporal variations in gully length were mainly driven by cumulative precipitation. Measurement of sediment deposition at 29 fascines in 2016 showed that only 47% of the fascines functioned as sediment sinks. They stored on average 1.7Mg of sediment per winter half-year, corresponding to 0.009Mgha−1. The results suggest that fascines positively impact the landscape's resilience and reduce ephemeral gully erosion rates. The use of vegetation barriers such as fascines are increasingly implemented for erosion control in western Europe, but pose problems for the management of open-field landscapes.

SUSTAINABILITY ANALYSIS OF MANGROVE ECOSYSTEM FOR ECOFISHERYTOURISM IN SIDOARJO LUMPUR ISLAND

Sidoarjo Lumpur Island is an artificial island created as a solution to the handling of sediment deposition in Porong River Estuary as a result of the mudflow which flowed into the sea via the Porong River. Lumpur Island is currently utilized as a habitat for mangrove ecosystem extension as well as a site for aquaculture with wanamina system (silvofishery). Ecofisherytourism is a way to utilize mangrove ecosystem for ponds silvofishery based on educational and economic approach to achieve the welfare of society. In addition, ecofisherytourism has a direct benefit of preserving nature and the environment. The research objective was to evaluate the condition of the mangrove ecosystem and analyze the physical condition of the Sidoarjo Lumpur Island as a reference in developing the island as ecofisherytourism region. The methods used were a combination of quantitative and qualitative methods. Data were collected through analysis of aerial photographs, field measurements, observation and documentation. Mangrove ecosystem conditions in Lumpur Island was classified as good to be utilized as ecotourism and fisherytourism . The highest elevation of the island is the tidal zone where mangroves grow well. Keywords: ecofisherytourism, mangrove, silvofishery

Wooden Building Damage Analysis in Mashiki Town for the 2016 Kumamoto Earthquakes on April 14 and 16

The 2016 Kumamoto earthquakes caused serious building damage in Mashiki town. Because two large earthquakes occurred within an interval of 28 hours, it is difficult to separate the damage caused by each of these earthquakes. We analyzed aerial photos of the center of Mashiki town taken before and after the second event, which allow us to separate the damage caused by the two earthquakes. Our analysis shows that building damage was concentrated especially on the river terrace of the Akitsu river, and there were almost no collapsed buildings in the south of the damaged area. The pattern of damage distribution of the two events was similar, which suggests that the damage to the wooden buildings was caused by local conditions. The analysis of past aerial photos showed that the heterogeneity of the damage distribution is difficult to explain by only the building age. The cause of this heterogeneity was found to be not because of an earthquake faulting effect, but because of a combination of building seismic performance and local site conditions.

Integration of the Cropland Data Layer Based Automatic Stratification Method into the Traditional Area Frame Construction Process

A new automatic stratification method utilizing United States Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) geospatial Cropland Data Layers (CDLs) was recently implemented in NASS operations. Recent research findings indicated that using the automated stratification method significantly improved Area Sampling Frame (ASF) stratification accuracies in intensively cropped areas (>15% cultivation) and overall stratification accuracies when compared to traditional stratification based on visual analysis of aerial photography or satellite data , while reducing the cost of ASF construction (Boryan et al., 2014). Though the new automated stratification method has improved stratification efficiency, objectivity, accuracy in the intensively cropped areas it inherits the CDL classification errors and has lower accuracies in low or non-agricultural areas. This implies that the automated stratification process is not a perfect solution to directly replace the NASS traditional stratification method for ASF construction operationally. This paper describes a hybrid approach: an operational ASF construction process that integrates the automated stratification results with ASF editing/review methods. New 2014 - 2015 NASS ASFs for South Dakota, Oklahoma, Arizona, New Mexico, Georgia, Alabama and North Carolina were successfully built using the new integrated operational process. The seven updated ASFs delivered significant improvements in objectivity, operational efficiency, and frame accuracy, based on 2014 and 2015 June Area Survey (JAS) reported data.

Landslide inventory, Teziutlán municipality, Puebla, México (1942–2015)

ABSTRACTThis article describes the spatial distribution of landslides in Teziutlán, Puebla, Mexico, which has been historically affected by mass movement processes. The most significant disaster associated with landslides in October 1999. Rainfall-triggered landslides and floods caused more than 100 deaths in Teziutlán and economic losses of US$233 million in Sierra Norte de Puebla. A multi-temporal landslide inventory map (1:25,000) for the period 1942–2015 was constructed by means of field observation and the analysis and interpretation of aerial photographs and satellite images. The inventory map includes 662 landslides and covers 163 km2. The total landslide area is in the order of 0.71 km2. Taking into account the scarp, channel and depositional area, the mean surface of the landslides is 1075 m2. The largest documented area was 17,512 m2. The smallest landslide area mapped was 24 m2. Most movements can be considered as having been small.

Detecting, mapping and classifying wetland fragments at a landscape scale

Small valley-bottom wetlands (<5km2) are often overlooked in conservation and restoration efforts due to the difficulty to discriminate them in large regions. However due to their position in the landscape they are both critical for ecosystem service provision as well as highly threatened. Therefore there is a need to detect and map the extent of small valley-bottom wetlands to aid conservation and restoration efforts. We investigated five research questions concerning small, valley-bottom palmiet wetlands in the Cape Floristic Region (CFR), South Africa: (1) What is the best technique to detect palmiet wetlands?, (2) what is the best approach to map their extent?, (3) how best to analyse their potential extent and historical changes?, (4) what is their current extent and distribution and how has this changed historically?, and (5) what are the main drivers of this change? We used three different approaches to answer the various questions: multispectral imagery (the Landsat series) combined with Support Vector Machine classification, aerial photograph analysis with photographs from three time-steps and predictive modelling of wetland habitat suitability (using the MaxEnt model). Our main findings suggest that (1) multispectral classification using Landsat8 was best for palmiet wetland detection (76% accuracy), whereas (2) aerial photographs were the most useful in mapping extent. (3) Analysing changes in extent over time was best achieved using aerial photography, due to their high resolution and long historical record in South Africa (1940 compared to 1970 in the Landsat series). (4) South African palmiet wetlands are in decline, having decreased by on average 31% in area since the 1940/50s (overall loss of 6.36km2). Palmiet wetlands have also become increasingly fragmented, with weighted wetland perimeter increasing by 29% over the same period. (5) The major driver of this appears to be gully erosion triggered by land-use change. The wider implication of these findings is that it is possible to detect small wetlands using freely available Landsat8 data which could be useful to support local or regional conservation and restoration initiatives.

The paradoxical evolution of runoff in the pastoral Sahel: analysis of the hydrological changes over the Agoufou watershed (Mali) using the KINEROS-2 model

Abstract. In recent decades, the Sahel has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as the Sahelian paradox, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated Sahel. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral Sahel. The kinematic runoff and erosion model (KINEROS-2) is applied to the Agoufou watershed (245 km2), in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the past case (1960–1975) preceding the Sahelian drought and the present case (2000–2015). Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1) a partial crusting of isolated dunes, (2) an increase of drainage network density, (3) a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4) important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual discharge between the past and the present case (p value &lt; 0.001), which is consistent with observations, despite a slight overestimation of the past discharge. Mean annual discharges are estimated at 0.51 × 106 m3 (2.1 mm yr−1) and 3.29 × 106 m3 (13.4 mm yr−1) for past and present, respectively. Changes in soil properties and vegetation cover (tiger bush thickets and grassland on shallow sandy soil) are found to be the main factors causing this increase of simulated runoff, with the drainage network development contributing to a lesser extent but with a positive feedback. These results shed a new light on the Sahelian paradox phenomenon in the absence of land use change and call for further tests in other areas and/or with other models. The synergetic processes highlighted here could play a role in other Sahelian watersheds where runoff increase has been also observed.

Remote Sensing of Chaco Roads Revisited

ABSTRACTThis paper reports on the first and highly effective use of Light Detection and Ranging (lidar) technology to document Chaco roads, monumental linear surface constructions of the precolumbian culture that occupied the Four Corners region of the American Southwest between approximately AD 600 and 1300. Analysis of aerial photographs supplemented by ground survey has been the traditional methodology employed to identify Chaco roads, but their traces have become increasingly subtle and difficult to detect in recent years due to the impacts of natural weathering, erosion, and land development. Roads that were easily visible in aerial photography and on the ground in the 1980s are now virtually invisible, underscoring the need for new, cutting-edge techniques to detect and document them. Using three case studies of the Aztec Airport Mesa Road, the Great North Road, and the Pueblo Alto Landscape, we demonstrate lidar's unprecedented ability to document known Chaco roads, discover previously undetected road segments, and produce a precise quantitative record of these rapidly vanishing features.

SUSTAINABILITY ANALYSIS OF MANGROVE ECOSYSTEM FOR ECOFISHERYTOURISM IN SIDOARJO LUMPUR ISLAND

&lt;p&gt;&lt;em&gt;Sidoarjo &lt;/em&gt;&lt;em&gt;Lumpur&lt;/em&gt;&lt;em&gt; Island is an artificial island created as a solution to the handling of sediment deposition in Porong River Estuary as a result of the mudflow which flowed into the sea via the Porong River. Lumpur Island is currently utilized as a habitat for mangrove ecosystem extension as well as a site for aquaculture with wanamina system (silvofishery). Ecofisherytourism is a way to utilize mangrove ecosystem for ponds &lt;/em&gt;&lt;em&gt;silvofishery&lt;/em&gt;&lt;em&gt; &lt;/em&gt;&lt;em&gt;based on educational and economic approach to achieve the welfare of society. In addition, ecofisherytourism has a direct benefit of preserving nature and the environment. The research objective was to evaluate the condition of the mangrove ecosystem and analyze the physical condition of the Sidoarjo Lumpur Island as a reference in developing the island as ecofisherytourism region. The methods used were a combination of quantitative and qualitative methods. Data were collected through analysis of aerial photographs, field measurements, observation and documentation. Mangrove ecosystem conditions in Lumpur Island was classified as good to be utilized as ecotourism and &lt;/em&gt;&lt;em&gt;fisherytouris&lt;/em&gt;&lt;em&gt;m . The highest elevation of the island is the tidal zone where mangroves grow well.&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;em&gt; &lt;/em&gt;&lt;/p&gt;&lt;strong&gt;&lt;em&gt;Keywords:&lt;/em&gt;&lt;/strong&gt;&lt;em&gt; ecofisherytourism, mangrove, silvofishery&lt;/em&gt;

Snow-avalanche impact craters in southern Norway: Their morphology and dynamics compared with small terrestrial meteorite craters

This regional inventory and study of a globally uncommon landform type reveals similarities in form and process between craters produced by snow-avalanche and meteorite impacts. Fifty-two snow-avalanche impact craters (mean diameter 85m, range 10–185m) were investigated through field research, aerial photographic interpretation and analysis of topographic maps. The craters are sited on valley bottoms or lake margins at the foot of steep avalanche paths (α=28–59°), generally with an easterly aspect, where the slope of the final 200m of the avalanche path (β) typically exceeds ~15°. Crater diameter correlates with the area of the avalanche start zone, which points to snow-avalanche volume as the main control on crater size. Proximal erosional scars (‘blast zones’) up to 40m high indicate up-range ejection of material from the crater, assisted by air-launch of the avalanches and impulse waves generated by their impact into water-filled craters. Formation of distal mounds up to 12m high of variable shape is favoured by more dispersed down-range deposition of ejecta. Key to the development of snow-avalanche impact craters is the repeated occurrence of topographically-focused snow avalanches that impact with a steep angle on unconsolidated sediment. Secondary craters or pits, a few metres in diameter, are attributed to the impact of individual boulders or smaller bodies of snow ejected from the main avalanche. The process of crater formation by low-density, low-velocity, large-volume snow flows occurring as multiple events is broadly comparable with cratering by single-event, high-density, high-velocity, small-volume projectiles such as small meteorites. Simple comparative modelling of snow-avalanche events associated with a crater of average size (diameter 85m) indicates that the kinetic energy of a single snow-avalanche impact event is two orders of magnitude less than that of a single meteorite-impact event capable of producing a crater of similar size, which is consistent with the incremental development of snow-avalanche impact craters through the Holocene.

Identyfikacja obiektów antropogenicznych na archiwalnych zdjęciach lotniczych okolic Jedwabnego

In connection with the research conducted by the Institute of National Remembrance relating to the participation in the murder of Polish citizens of Jewish nationality on 10 July 1941 in Jedwabne, in 2002 the Institute of Geodesy and Cartography provided an expertise in the field of the anthropogenic object detection in the Jedwabne area. The article presents the methodology and results of the analysis of archival aerial photographs concerning the assessment of anthropogenic forms. The results confirm a significant role played by archival aerial photographs in retrospective analyses. The use of aerial photographs usually enables a more accurate description of the site compared to a topographic map. Aerial photographs make it possible to register a complete picture of all the elements present on the surface of the earth at a specific time. This creates a possibility to detect constructions and historical areas with details greater than by comparing maps and documents from various periods, which makes archival aerial photographs a valuable source of historical-geographical studies.

Diurnal to Decadal Changes in the Balance between Vegetation and Bare Ground in Tasmanian Fjaeldmark

ABSTRACTPeriglacial processes are active under current climatic conditions on the more exposed peaks and ridges of Tasmania’s high country. Non-sorted steps, stripes, and solifluction lobes with vegetated risers and bare treads have formed on many of the mountains capped in fissile sedimentary rocks. Any disturbance to the balance between vegetation and bare ground can result in biogeomorphic feedbacks leading to an increase or decrease in periglacial activity and thereby threaten the survival of fjaeldmark. We tested the hypotheses that vegetation helps create risers by capturing material moved by needle ice, water, and wind, and that the balance between vegetation and bare ground in fjaeldmark is dynamic in Tasmania at the decadal time scale. Repeat photo plots and temperature data loggers were employed to monitor the dynamism of two non-sorted lobes on Mount Rufus over a seven-month period. Diurnal freeze/thaw cycles resulted in needle ice formation on the bare treads and promoted downslope movement of the surface layer through frost creep. Vegetation was observed to reduce geomorphic activity and to capture soil and clasts transported downslope, thereby steepening the risers. Aerial photographic analysis showed a 0.065% per annum increase in vegetation cover in fjaeldmark since the mid-20th century. Mountains that had a high number of days with snow cover were especially prone to increases in vegetation cover. Decline in vegetation cover occurred on some mountains burned during the past century. The smallest changes occurred on the most exposed peaks and ridges.

Morphology of the Raised Shore Platforms along the Coastline between Daghmar and Dhabab, Sultanate of Oman

Raised shore platforms, are rocky surfaces formed by wave action and subaerial weathering during global high sea level stands. The present height of the raised shore platforms is attributed to several factors, mainly to eustatic sea level changes, isostatic changes in the relative level of land and sea, and vertical tectonic activities. The aim of this study is to investigate the detailed morphology of the raised shore platform along the rocky coastline between Daghmar and Dhabab, in the southeastern part of Muscat Governorate. The study also intends to establish a tentative chronology of the raised shore platforms development. The methodology is based on field observation and documentation, along with satellite and aerial photographs analysis. The results have shown that the study area has a sequence of five successive, well developed raised shore platforms and well preserved, except the platform at 10m altitude which is only found in isolated fragments. The formation of the raised shore platforms has been affected by a number of constructive factors including tectonic activity, and destructive factors such as fluvial action and subaerial weathering. No absolute dating has been reported or can be obtained from the study area, due to its erosional nature. However, dating from the shorelines adjacent to the study area, ranging in heights from 3 to 15m above sea level, revealed a narrow range of 26,400 to 29,600 years. This period coincides with the last glaciations when the sea level was at about 75m below the present level, and thus did not match with the altitudes of the platforms. This suggests that the platforms could be belong to the last interglacial high sea level, when the sea level stood at about 6m above the present level. Based on this scenario, the study concludes that the coastline of the study area has not experienced any significant uplift during the Late Quaternary.

Morphology of the Raised Shore Platforms along the Coastline between Daghmar and Dhabab, Sultanate of Oman

Raised shore platforms, are rocky surfaces formed by wave action and subaerial weathering during global high sea level stands. The present height of the raised shore platforms is attributed to several factors, mainly to eustatic sea level changes, isostatic changes in the relative level of land and sea, and vertical tectonic activities. The aim of this study is to investigate the detailed morphology of the raised shore platform along the rocky coastline between Daghmar and Dhabab, in the southeastern part of Muscat Governorate. The study also intends to establish a tentative chronology of the raised shore platforms development. The methodology is based on field observation and documentation, along with satellite and aerial photographs analysis. The results have shown that the study area has a sequence of five successive, well developed raised shore platforms and well preserved, except the platform at 10m altitude which is only found in isolated fragments. The formation of the raised shore platforms has been affected by a number of constructive factors including tectonic activity, and destructive factors such as fluvial action and subaerial weathering. No absolute dating has been reported or can be obtained from the study area, due to its erosional nature. However, dating from the shorelines adjacent to the study area, ranging in heights from 3 to 15m above sea level, revealed a narrow range of 26,400 to 29,600 years. This period coincides with the last glaciations when the sea level was at about 75m below the present level, and thus did not match with the altitudes of the platforms. This suggests that the platforms could be belong to the last interglacial high sea level, when the sea level stood at about 6m above the present level. Based on this scenario, the study concludes that the coastline of the study area has not experienced any significant uplift during the Late Quaternary.

Mapping an ancient qanat system in a northern Arabian urbanized oasis

As an obsolete underground water supply system, the qanāt is particularly affected by the destruction and demolition taking place within the oases of Saudi Arabia. In a period of economic and demographic growth, the oasis of Dūmat al-Jandal (province of Jawf) is a good example of such an evolution. Qanāts have been replaced by everdeeper pumping systems since the mid-twentieth century, and the series of shafts associated with these monumental structures, well known elsewhere in the Middle East, are no longer visible from the surface, primarily for reasons of security. The investigation conducted since 2011 by the Saudi–Italian–French archaeological project in Dūmat al-Jandal provides a first image of the ancient hydraulic network through a combination of complementary analyses integrated into a GIS: field surveys, oral information gathering, underground exploration, analysis of old aerial photographs and comparison with recent satellites images.

Geology and mass movements of the Licetto River catchment (Calabrian Coastal Range, Southern Italy)

ABSTRACTThe paper presents a detailed mass movement inventory map of the Licetto River basin, an intermountain catchment of 50 km2 formed during the Quaternary in response to extensional tectonics dissecting fold-and-thrust belts of the Calabrian Coastal Range (Southern Italy). The map (Main Map) is the result of both an integration between geological and morphological data derived from the visual analysis of aerial photographs at different times and scales, and the collection of new data obtained from multi-temporal field surveys. The study area is affected by a total of 824 mass movements, frequently made by superimposed bodies of different types, states of activity and sizes, including some kilometre-scale Deep-Seated Gravitational Slope. The majority of the mapped landslides, mainly of slide type, involve low-grade metamorphic rocks which also show the exclusive presence of deep-seated gravitational slope deformations. Analysis of the inventory map revealed that 40% of the mapped landslides, often attributable to very slow-moving landslides, can be considered active. The Main Map represents a useful tool for territorial planning and engineering – geological and environmental purposes in this complex geo-structural area, providing a useful contribution for quantitative landslide risk analyses and the design of appropriate risk-mitigation measures.

River regulation and riparian woodlands: Cottonwood conservation with an environmental flow regime along the Waterton River, Alberta

AbstractFollowing water withdrawal, riparian cottonwoods have declined downstream from some dams in western North America. Analyses of aerial photographs and field observations in the 1980s suggested that the black and narrowleaf cottonwoods (Populus trichocarpa and Populus angustifolia) along the Waterton River, Alberta, were declining due to drought stress following the 1964 damming and diversion. This raised concern for the riverine ecosystems and in 1991, “functional flows” commenced with 2 changes: (a) the minimum flow was increased from 0.9 to 2.3 m3/s (mean discharge 21.9 m3/s) and (b) flow ramping provided gradual stage recession after the spring peak. This provided an environmental flow regime that was delivered for 2 decades and this study investigated the consequent river flow patterns and riparian woodlands upstream and downstream from the Waterton Dam. Analyses of aerial photographs from 1951 to 2009 assessed 4 flow management intervals: (a) the free‐flowing predam condition, (b) the initial dammed interval to the mid‐1970s, (c) a drought interval in the 1980s, and (d) with the environmental flow regime after 1991. Analyses revealed woodland reduction from 1961 to 1985 due to losses through bank erosion with major floods and apparent decline due to low flows following a regional drought and water withdrawal for irrigation. With the subsequent environmental flow regime, there was apparent woodland recovery, despite drought in 2000 and 2001. This study demonstrated that the correspondence between river flow patterns and the extent of riparian woodlands and the benefit from the environmental flow regime that probably reduced drought stress and mortality.

Tectonic constraints on a deep-seated rock slide in weathered crystalline rocks

Deep-seated rock slides (DSRSs), recognised as one of the most important mass wasting processes worldwide, involve large areas and cause several consequences in terms of environmental and economic damage; they result from a complex of controlling features and processes. DSRSs are common in Calabria (southern Italy) where the complex geo-structural setting plays a key role in controlling the geometry of the failure surface and its development. This paper describes an integrated multi-disciplinary approach to investigate a DSRS in Palaeozoic high-grade metamorphic rocks of the Sila Massif; it focuses on the definition of the internal structure and the predisposing factors of the Serra di Buda landslide near the town of Acri, which is a paradigm for numerous landslides in this area. An integrated interdisciplinary study based on geological, structural, and geomorphological investigations—including field observations of weathering grade of rocks, minero-petrographic characterisations, geotechnical investigations and, in particular, fifteen years of displacement monitoring—is presented. Stereoscopic analysis of aerial photographs and field observations indicate that the Serra di Buda landslide consists of two distinct compounded bodies: (i) an older and dormant body (~7ha) and (ii) a more recent and active body (~13ha) that overlies the previous one. The active landslide shows movement linked to a deep-seated translational rock slide (block slide); the velocity scale ranges from slow (1.6m/year during paroxysmal stages) to extremely slow (<16mm/year during stable creep stages). The geological structures and rock weathering have played a key role in the landslide's initiation and further development. Steep slope angles, rugged topography, river deepening and erosion at the toe of the slope are also responsible for the formation of this landslide. In particular, the landslide shows a strongly tectonic constraint: the flanks are bounded by high-angle faults, and the main basal failure surface developed inside an E–W southward-dipping thrust fault zone. The entire active rock mass (total volume of approximately 6Mm3) slid at one time on a failure surface that dipped<27°, and the maximum depth, as determined by inclinometer measurements, was approximately 58m. Petrographic and mineralogical analyses suggest that the rocks in the thrust zones, where the failure surfaces develop, are highly affected by weathering processes that significantly reduce the rock strength and facilitate the extensive failure of the Serra di Buda landslide. Finally, the landslide's internal structure, according to geotechnical investigations and displacement monitoring, is proposed. The proposed approach and the obtained results can be generalised to typify other deep landslides in similar geological settings.