John R. Giardino

Engineering geomorphology of rock glaciers

A partnership between geomorphology and engineering is facilitating human development in this harsh environment. Rock glaciers provide locations for urban water sources, construction borrow sources, drill sites, shaft and tunnel portals, ski tower supports, and dam abutments. Rock glaciers, as dynamic landforms, necessitate proper identification in the field. Placing structures on, in, or adjacent to rock glaciers requires an appreciation and understanding of their temporal stability. Internal and surface characteristics provide important clues to the development and deformation of rock glaciers. Rock glaciers play a significant role in the alpine debris transport system. Active movement and mass wasting are perhaps the most obvious geologic hazards affecting engineered works. The structure of the rock glacier is conducive to the production of a steady, continuous supply of meltwater during summer months. Thus, rock glaciers serve as alpine aquifers. Consideration of rock glaciers as potential aquifer sources requires caution because of the long-term impact of climate change on the temporal nature of the landform. From the rock glaciers that we have monitored for water quality characteristics, it appears that they provide quality potable water. This paper provides a foundation for appreciation and understanding of rock glaciers from an engineering geomorphologic point of view. The approach taken in this paper provides practical, important information to aid the engineer and engineering geologist in prudent evaluations of rock glaciers as potential sites for human development and uses. The bottom line of our paper is: rock glaciers must be avoided for essentially all structures.

GPR survey of a lobate rock glacier in Yankee Boy Basin, Colorado, USA

Abstract The internal structure of a lobate rock glacier located in the San Juan Mountains of southwest Colorado was investigated using ground penetrating radar (GPR). A 440 m, 25 MHz longitudinal profile oriented along the central axis of the rock glacier shows moderate to strongly coherent reflection horizons or layers that can be recognized clearly to a depth of 30–35 m. The layers are interpreted as representing ice-supersaturated sediments and coarse, blocky rockslide debris that are the result of flow, perhaps generated by seasonal snow pack covered by episodic debris flows or high-magnitude discharges of talus from the cirque headwall. Profiles collected at 50 MHz indicate that, in the upper 20 m thickness of the rock glacier, many of these layers are laterally continuous. The total depth of penetration (∼40 m at 25 MHz) was sufficient to detect the rock glacier-cirque-floor contact, which is composed of underlying moraine. Several prominent reflection events that subdivide the profile into broad 10–15 m-thick layers represent contacts between major depositional units. These units are believed to be individual flow lobes that were initiated at various cirque-headwall locations. We interpret this rock glacier to be a composite feature that formed by a process involving the development and subsequent overlap of discrete flow lobes that have over-ridden older glacial moraine and protalus rampart materials. The latter materials have been incorporated into the present flow structure of the rock glacier.

Suitability Assessment for New Minia City, Egypt: A GIS Approach to Engineering Geology

Urban development is a high priority in Egypt. New Minia City, located on the eastern bank of the Nile River, approximately 250 km south of Cairo, is one of 16 new development communities. Urban development in New Minia City may encounter several geo-environmental problems. Karst conditions and structural features in the local heterogeneous bedrock limit its suitability for constructional purposes. In this research, suitability of the area for urban development was assessed using a geographic information systems (GIS)-based approach. A weighted GIS model that incorporated land use/cover, types of soil, karst feature distribution, fracture densities, slopes, distances to major faults and streams, road network, and city boundaries was established to create a map of site suitability for the city. Model weights were developed using the analytical hierarchy process (AHP) approach. Current urban land use within New Minia City falls into four classes of suitability. Approximately 7 percent of the area built by 2002 is in the low suitability class, which suggests that the map of site suitability can serve as a reliable base for planning sustainable development in New Minia City. The developed map of site suitability is effective for assessing and revealing ratings of suitability for urban development. Furthermore, the map of suitability provides the foundation for informed decision making in the development of New Minia City.

Mapping geomorphology : A journey from paper maps, through computer mapping to GIS and Virtual Reality

Abstract Maps are integral components of research in geomorphology and Quaternary geology. Visual presentation of the spatial and temporal distribution of a phenomenon often provides clues to the process(es) that generated the phenomenon. Compiling information on maps, interpreting spatial patterns, and using standard topographic maps were fundamental parts of the undergraduate experience. Why have such experiences been slowly disappearing from undergraduate curricula? How are geology majors taught map scale, map projections, and the pitfalls associated with the display of spatial information? Neglect in preserving the mapping tradition places the geology major at a disadvantage. The use of maps and mapping is undergoing a renaissance; use in the classroom has a bright future because of digital scanning, computer cartography, geographic information systems (GIS), and virtual reality. Pen and ink techniques should be relegated to museums. Pencil sketches can be scanned and perfect products generated every time. These techniques, however, do not eliminate the need for basic map knowledge such as scale, projections, and generalization. What assumptions about map projections have been built into the software? How are spatial data and attribute data integrated into the resultant map in a geographic information system (GIS)? Because the application of virtual reality to geomorphic processes looms on the horizon, geologists must recognize how the current spatial revolution can help with the assessment of geologic phenomena and teach students to function with the new technology.

Land subsidence in the Nile Delta of Egypt observed by persistent scatterer interferometry

Land subsidence is a common problem in vulnerable deltas. The Nile Delta is no exception. The impacts of land subsidence are heightened by the economic, social and historical importance of the delta to Egypt. A major debate has evolved in the past two decades concerning whether the land surface of the Nile Delta is subsiding. The debate is certainly problematic in light of the fact that current measures of subsidence across the delta are rough estimates at best. To date, knowledge of subsidence rates in the delta is limited to long-term geologic averages that assume spatial uniformity and temporal consistency. In this study, we apply persistent scatterer interferometry (PSI) to measure the magnitude and monitor the spatial and temporal variations of land subsidence in the Nile Delta, during 1993–2000, using synthetic aperture radar interferometric data of 5.66 cm wavelength. The average measured rates of local subsidence in two major cities in the delta, namely Mansura and Greater Mahala, are –9 and –5 mm year–1, respectively. The observed deformation features imply that subsidence in both cities is controlled mainly by local groundwater processes. Our PSI measurements indicate that no regional subsidence has occurred in either city between 1993 and 2000. The slight regional subsidence that is expected to occur over time due to the natural compaction of deltaic sediments most likely has been masked by surface displacements caused by seasonal oscillations in the groundwater level.

Poststorm Evolution of Beach-Dune Morphology: Padre Island National Seashore, Texas

ABSTRACT Weymer, B.A.; Houser, C., and Giardino, J.R., 2015. Poststorm evolution of beach-dune morphology: Padre Island National Seashore, Texas. The response and recovery of barrier islands to extreme storms and ultimately to relative sea-level rise depends on the height and extent of the foredunes relative to storm surge. The impact of storms is complicated by the tendency of dune morphology to vary alongshore at a range of spatial scales, and it is reasonable to assume that this variable response will be preserved within subsurface stratigraphy. We used ground-penetrating radar (GPR) and vibracores to investigate subsurface structures for foredunes of different heights within a 2.5-km section of beach at Padre Island National Seashore, Texas. Identical, laterally continuous radar reflectors were observed at each site at a depth of ~1.2 m and interpreted as a storm surface. Results from the smallest dune suggest that the dune experienced little net erosion during the storm but also exhibited the least recovery. The intermediate dune was completely eroded by the storm but also exhibited the greatest recovery through the migration of accretionary mounds driven by aeolian transport, leading to the development of embryo dunes forming the modern dune core. The largest dune was scoured at the base and experienced little poststorm recovery, except for beachface recovery. Thus, the response and recovery of adjacent, but morphologically distinct, dunes is quite different over the same sequence of storm activity. We suggest that the extent and form of beach-dune recovery is dependent on the impact scale of the storm and may represent a reinforced process once alongshore variations in dune height are initialized.

Water Deficit Duration and Severity Analysis Based on Runoff Derived from Noah Land Surface Model

AbstractThe identification and prediction of drought events depend on the integrity of the dataset employed. Streamflow is a good indicator of surface water availability and has dominated the literature on frequency analysis of hydrological droughts and water management. However, gauged measurements are impaired by climate and land use changes, especially in large, modified watersheds. Hence, their use in drought prediction is limited because they may violate the assumption of stationarity unless a naturalized observation series is obtained. In this paper, a land surface model is used to generate runoff in the Rio Grande/Rio Bravo del Norte basin. Land use land cover is kept constant so that changes are a result of climatological variations. The river threads across several climatic zones; therefore the basin is divided into different regions for analysis. Using statistical theory of runs, water deficit duration and severity and drought interarrival time are extracted from 3-month Standardized Runoff Inde...

The statistical study of hydraulic geometry: A new direction for compositional data analysis

Hydraulic exponents and unit hydraulic exponents are unit-sum constrained, which requires that they be analyzed by statistical methods designed for compositional data. Though uncertainties remain regarding selection of the “best” constraining operation and method of handling departures from the unit-sum constraint, neither category of uncertainty should be an impediment to the selection of the appropriate statistical methodology. In a small sample study, the hydraulic geometry of different types of streams were compared: (1) semi-arid: perennial vs. ephemeral; (2) tropical: Puerto Rico vs. West Malaysia; and (3) semi-arid vs. tropical (by pooling the previous data sets). All three comparisons revealed statistically significant differences in either logratio mean vectorsor logratio covariance matrices but not both. All six categories of data had logistic normal distributions. Because the derivatives at a given discharge of curvilinear hydraulic geometry relationships and hydraulic exponents on either side of the “breakpoints” of piecewise linear relationships are unit-sum constrained, they also can be studied by compositional methods. However, the compositional approach is limited in cases where distributions have large departures from logistic normality and for streams that have negative hydraulic exponents.

The decrease of lake Chad as documented during twenty years of manned space flight

Abstract Space photography has been sucessfully used to extend the space remote sensing data base for environmental monitoring by a decade. In this study of Lake Chad, space photographs were digitized and registered to a topographic base map before water classifications were performed. From 1966 to 1985 we observed over a 21,000 square kilometer decrease in lake surface area.

Logratio linear modelling of hydraulic geometry using indices of flow resistance as covariates

Abstract The exponents of hydraulic geometry relations are unit-sum constrained (i.e., a composition), thus, a class of statistical methods called compositional data analysis must be employed to obviate the problem of spurious correlation. One of these methods, logratio linear modelling, is capable of establishing either linear or non-linear functional dependency between a composition (e.g., hydraulic geometry exponents) and a covariate. In our study, logratio linear modelling of data from the literature did not establish correlations between at-a-station hydraulic geometry and median grain size (d50) of the bed material, stream roughness, nor drag resistance. The lack of a correlation between at-a-station hydraulic geometry and bed grain size is expected in streams where roughness is dominated by planform characteristics, vegetation elements, macroscale bar features, channel obstructions, or bedforms. The use of d84 in the Prandtl-von Karman “law of the wall” equation and in the Keulegan resistance equation, however, suggests that d84 might have been a more appropriate parameter to use than d50. The lack of a correlation between at-a-station hydraulic geometry and stream roughness (or drag resistance) is expected in streams where roughness elements become rapidly “drowned” at higher discharges. Hydraulic geometry, however, was shown to be a function of the rate at which stream roughness varies with discharge. Thus, to understand the complex interactions within fluvial systems, geomorphologists should examine the rates of change of stream parameters such as drag resistance, Mannings roughness coefficient, the Darcy-Weisbach friction factor, and grain size indices, in addition to the stream parameters themselves.