Drift Areas Research Articles

Early ontogenetic development of Cynodon gibbus (Characiformes: Cynodontidae) in the Amazon River basin

Abstract Knowledge regarding the early life history of neotropical fish, although incipient, is crucial for the accurate identification of larvae collected from the natural environment. Such details are important for defining spawning, drift, and nursery areas as well as the reproductive periods of species. Herein, the larval development of Cynodon gibbus was described using morphological, meristic, and morphometric characteristics. Specimens were collected from open water limnetic zones and under macrophyte stands in the Amazon basin from 2010 to 2023. Forty-eight larvae with standard lengths ranging from 5.73 to 21.57 mm were studied. The larvae have a long to very long body, small eyes, and a small head, which progresses to a moderate size in the preflexion stage. Furthermore, the larvae had ample mouths with numerous conical teeth, an oval-triangular swim bladder, overlapping dorsal and anal fins, and the tip of the pectoral fin not reaching the swim bladder. Pigmentation pattern comprised two punctate pigments above the fontanelle, the rectum, and at the lower and upper ends of the caudal peduncle. Various body parts exhibited predominant allometric relationships, reflecting differential developmental rates among them in response to fundamental ecological requirements for survival. The C. gibbus larvae can be identified by a combination of the position of dorsal, anal and pectoral fins, pigmentation pattern, swim bladder shape, and the total number of myomeres (51 to 53).

Modern and Relict Evidence of the Iceberg Scouring at the Bottom of the Barents and Kara Seas

The article systematizes and summarizes published data on the parameters and distribution areas of modern and relict iceberg scours (or plough marks), as well as on the maximum possible sizes and drift areas of modern icebergs in the Barents and Kara Seas. According to the open-source bathymetric data, for the first time the analysis of “throughput” of the waters in front of modern glaciers was carried out. Based on summarized and established facts, areas of the most likely distribution of modern iceberg effects on the bottom are determined by the method of expert assessment. This work is relevant both from a fundamental point of view and for determining the current depths limits of iceberg scouring at the bottom of the Barents and Kara Seas, which is important for ensuring the geoecological safety of all kinds of activities on the sea shelf.

Representation of sea ice regimes in the Western Ross Sea, Antarctica, based on satellite imagery and AMPS wind data

Sea ice drift data at high spatial resolution and surface wind model output are used to explore atmosphere-sea ice interactions in the Western Ross Sea including the three main polynyas areas; McMurdo Sound polynya (MSP), Terra Nova Bay polynya (TNBP), and the Ross Sea polynya (RSP). This study quantifies the relationship between the winds and sea ice drift and observes the average and annual anomalies across the region. Sea ice drift velocities are based on high-resolution (150 m) Advanced Synthetic Aperture Radar (ASAR) images from Envisat for winters between 2002 and 2012. Sea ice motion vectors were first correlated with the corresponding Antarctic Mesoscale Prediction System (AMPS) surface wind velocities, and the sensitivity of the spatial correlations and residuals were examined. Four drift parameters were selected (mean drift, the correlation between drift and wind, drift to wind scaling factor, and the directional drift constancy) to perform an unsupervised k-means classification to automatically distinguish six zones of distinctive sea ice characteristics solely based on ice drift and wind information. Results indicate a heterogeneous pattern of sea ice movement at a rate ranging from 0.41 to 2.24% of the wind speed in different areas. We also find that the directional constancy of sea ice drift is closely related to the wind fields. Sea ice drift and wind velocities display the highest correlation in free-drift areas (R = 0.70), followed by deformational drift zones (R = 0.54), and more random drift areas (R = 0.28). The classification illustrates the significance of localized wind-driven sea ice drift in this coastal area resulting in zones of convergence, shear, and free drift. The results also indicate that the most persistent patterns of sea ice motion are near the RSP and TNBP areas, both being driven by strong localized winds. Our findings identify that large-scale sea ice motion is predominantly wind-driven over much of the study area while ocean currents play only a minor role.

Underground Mine Tunnel Modelling Using Laser Scan Data in Relation to Manual Geometry Measurements

Underground mine tunnels, drifts, and mine headings are susceptible to the impact of convergence. The convergence has a big influence on further measurements such as airflow and the volume concentration of methane and other gases. In most cases, deformation of arch supports lead to getting a smaller cross-section area. A comparison is made between five methods of measuring the cross-sectional area of a mine tunnel. The reference size of the six cross-section mine drift areas were obtained by Terrestrial Laser Scanning, which were then compared with the cross-section areas obtained by four other methods. The following methods were considered: area calculation using CAD software, an empirical method, approximation by a semi-ellipse and approximation by a semi-ellipse with attached straight sections. This article presents the quantitative and qualitative differences of the obtained results. Differences in the calculated cross-sectional areas of the mine drift are discussed, and reasons for the differences are determined. In addition, the advantages and disadvantages of each method are indicated.

Spatio-temporal distribution of NDVI and its influencing factors in China

Normalized Difference Vegetation Index (NDVI) is an important indicator reflecting the state of regional climate and environment, which is affected by precipitation, temperature, soil water content, and so on. This study analyzed the influence of different factors on NDVI through the spearman correlation coefficient (SCC) and standard regression coefficient (SRC), carried out climate zoning in China through principal component analysis (PCA) and cluster analysis, simulated the NDVI value through deep learning algorithm, and analyzed the spatial mutation positions of different factors through concept drift detection. The research results show that the main factor that affects NDVI in most areas of China is surface soil moisture (SSM), followed by temperature, while in arid areas root zone soil moisture (RZSM) and profile soil moisture (PSM) are the main influencing factors. The climate zones of China can be roughly divided into northern, southern and northwestern inland areas, while there are transitional zones between different main zones. The deep learning algorithm can simulate the NDVI value very well, and the Nash efficiency coefficients (NSE) during training and verification periods are 0.893 and 0.833, respectively. However, the details of some areas are rough. This shows that the selected impact factors can basically determine the status of NDVI, and these impact factors can be used to predict the changes in NDVI. The environmental drift areas discovered by concept drift detection are mainly in the Heilongjiang River Basin in Northeastern China, Yunnan, Sichuan, and Southern Tibet in Southwestern China, and Gansu, Qinghai and Xinjiang in Northwestern China. This study provides an important reference for the analysis of environmental regional zoning, climate change detection and simulation.

Snowdrift Landscape Patterns: An Arctic Investigation

AbstractBetween 2012 and 2018 we mapped near‐peak seasonal snow depths across two swaths covering 126 km2 in Northern Alaska using aerial structure‐from‐motion photogrammetry and lidar surveys. The surveys were validated by over a hundred thousand ground‐based depth measurements. Using a quantitative method for identifying drift areas, we conducted a snowdrift census that showed on average 18% of the study area is covered by snowdrifts each winter, with 40% of the snow‐water‐equivalent contained in the drifts. Within the census we identified six types of drifts, some of which fill each winter, others which do not. The seasonal drift evolution was distinctly different in the two swaths, a result largely explained by topographic differences. Using four metrics from the field of image quality analysis, we tested the year‐to‐year fidelity of these drift patterns, finding overall high year‐to‐year similarity, but with higher similarity values for filling drifts, and higher similarity values in one swath versus the other, again a function of the topography. These high drift fidelity values are best explained by climatically convergent winter‐cumulative windblown snow fluxes interacting with drift traps to produce the same drifts year after year. However, due to the existence of filling versus nonfilling drifts, and a predicted increasing frequency of rain‐on‐snow events in the Arctic, future snowdrift patterns and drift evolution pathways in the Arctic could diverge from those of today, with direct hydrologic impacts.

Morphodynamic Response to Low-Crested Detached Breakwaters on a Sea Breeze-Dominated Coast

Low-crested detached breakwaters (LCDBs) have been widely employed as a mitigation measure against beach erosion. However, only a few studies have assessed their performance in sea-breeze-dominated environments. This work investigates the beach morphodynamics behind LCDBs deployed on a micro-tidal sea-breeze-dominated beach. The study area, located in the northern Yucatán peninsula, is characterized by low-energy, high-angle waves, which drive a persistent (westward) alongshore sediment transport (O(104) m3/year). High-resolution real-time kinematics global positioning system (GPS) beach surveys were conducted over a one-year period (2017–2018) to investigate the performance of LCDBs at three sites. Moreover, unmanned aerial vehicle flights were employed to evaluate far-field shoreline stability. Field observations revealed a distinct behavior in the three study sites, dependent on the breakwaters’ transmission characteristics, geometry, stability, and shoreline orientation. Impermeable LCDBs, made of sand-filled geosystems, induced significant beach accretion (erosion) in up-(down-)drift areas. On the other hand, permeable LCDBs, made of Reef Ball™ modules, induced moderate beach changes and small erosion in down-drift areas owing to higher transmission coefficients. Measurements of LCDBs’ freeboard height show that sand-filled geosystems’ breakwaters presented a significant loss of sand during the study period, which explains the unexpected beach morphodynamic response on the lee side of the structure. Observations suggest that the study area is highly sensitive to the presence of LCDBs with low transmissivity.

XXIII Международный симпозиум Нанофизика и наноэлектроника", Нижний Новгород, 11-14 марта 2019 г. Вертикальный полевой транзистор с управляющим p-n-переходом на основе GaAs

The first results on the creation of an original power GaAs field-effect transistor with a vertical channel controlled by the p-n junction are presented. The main technological feature is the use of two separate processes of epitaxial growth in the formation of the transistor structure. The part of the transistor containing the drain, drift and gate areas is grown by liquid-phase epitaxy. The technology of organometallic gas-phase epitaxy is used to form the areas of the channel and the source.

Groins or Not: Some environmental challenges to urban development on a Lagos coastal barrier island of Lekki Peninsula

Worldwide, barrier islands which protect mainland areas are usually sedimentary, dynamic and in great demand for urban development. Intense development on them negates their dynamics leading to risks which necessitate protective measures such as groins which tend to aggravate the problem. Suburban Lekki Peninsula on the south of Lagos metropolis is a large, long barrier island disposed largely to unplanned, accelerated growth since the inception of Lekki Scheme 1 in 1980, all without any consideration of its physical dynamics. This study therefore assessed and evaluated some risks confronting development from the dynamics of the Peninsula with the goal of demonstrating the use of low - budget online data for analysis of coastal hazards and risks. The methodology entails the integration of remote sensing, GIS techniques to assess its characteristics and evaluate risks to development from some hazards inherent in island's physical processes as a typical barrier island on the Lagos coastline. Findings reveal that the area which was 0.5% built up in 1984 had grown to about 18% in 2014 with Eti-Osa LGA as the most developed at 68.4%. Results further confirm the Peninsula as narrow in a few sections and generally low-lying with 37% between 0.5 - 3m while 63% is between 3 - 5m above m.s.l. Eti-Osa LGA is the most low -lying of the three councils in the area with 0.5 - 3m height dominant. Medium to maximum rates of beach erosion occurs mainly in Eti-Osa LGA at about 22.75m/yr around Kuramo Waters, decreasing to 5.5m/yr around Goshen Estate. Projections on coastal erosion on the most erosive area in Eti-Osa LGA from 2013 reveal potential socio-economic impacts on road infrastructure and buildings as ranging from a minimum of N1.16billion to N139.42billion over the next 30 years at present level of development and values. The study concludes that the greatest threat and risk from barrier island processes assessed presently are mainly in Eti-Osa LGA with the old Maroko and Kuramo Waters as the epicenter. Among the recommendations toward continued occupation of the Peninsula are the base flood elevation (BFE) and design flood elevation (DFE) to enhance the resilience of future developments. Comparative observations from literature on effect of groins on down drift areas from the US were further dwelt on.

Impacts that cause the highest direct mortality of individuals do not necessarily have the greatest influence on temperate eel escapement

Temperate eels are three panmictic catadromous species with a long period of oceanic passive larval drift and large distribution areas in contrasting environments. Spatial patterns of life history traits have been observed, and are correlated with environmental gradients, and may arise from both adaptive phenotypic plasticity and genetic polymorphism. This raises the question of the effect of spatially heterogeneous anthropogenic pressures on these populations. In this context, we used Geneveel, an individual-based optimization model that includes both phenotypic plasticity and genetic polymorphism, to explore the effects of different kinds of anthropogenic pressures: glass eel and silver eel fisheries, obstacles to upstream migration, and turbine mortality. More specifically, we analyzed the effects of these pressures on five output variables: the number of escapees, the proportion of females, the proportion of slow growers, the mean length-at-silvering and the resulting egg production. Our results suggest that phenotypic plasticity could act as a compensatory mechanism that mitigates the effects of some pressures (glass eel fishery and obstacles to upstream migration) and could be a source of resilience for the population, while other pressures did not show any compensatory effect (silver eel fishery and turbine mortality). Therefore, global impacts are very hard to assess, and the pressure that kills the most individuals does not necessarily have the biggest impact on the spawning biomass.

Wake effects on drift in two-dimensional inviscid incompressible flows

This investigation analyzes the effect of vortex wakes on the Lagrangian displacement of particles induced by the passage of an obstacle in a two-dimensional incompressible and inviscid fluid. In addition to the trajectories of individual particles, we also study their drift and the corresponding total drift areas in the Föppl and Kirchhoff potential flow models. Our findings, which are obtained numerically and in some regimes are also supported by asymptotic analysis, are compared to the wakeless potential flow which serves as a reference. We show that in the presence of the Föppl vortex wake, some of the particles follow more complicated trajectories featuring a second loop. The appearance of an additional stagnation point in the Föppl flow is identified as a source of this effect. It is also demonstrated that, while the total drift area increases with the size of the wake for large vortex strengths, it is actually decreased for small circulation values. On the other hand, the Kirchhoff flow model is shown to have an unbounded total drift area. By providing a systematic account of the wake effects on the drift, the results of this study will allow for more accurate modeling of hydrodynamic stirring.

Estimation of Shear Wave Velocity in Drifts Using Multichannel Analysis of Surface Wave (MASW) Technique – A Case Study from Jammu & Kashmir, India

Abstract: Multichannel analysis of surface waves (MASW) is a non-destructive seismic prospecting method utilizing Rayleigh waves for imaging and characterizing shallow sub-surface structure. Multichannel analysis of surface waves (MASW) studies were conducted in drift areas of two bridge sites in the hilly terrain of J&K for imaging and characterizing shallow sub-surface structure. The purpose of the present study is to estimate the shear wave velocity (VS) and sub-surface structure in four drifts made in a hilly terrain for construction of two bridges. Rayleigh waves are having dispersive properties, travelling along or near the ground surface and are usually characterized by relatively low velocity, low frequency, and high amplitude. The study area comprises of Tertiary group of rocks which are underlain by Siwalik group. The main rock type in the study area is dolomite which has undergone various geological processes like weathering, jointing, fracturing and shearing. MASW data was collected inside four drifts in the mountainous terrain of J&K state which are located on either sides of Chenab river. The data was analyzed by relevant processing software using dispersion and inversion technique. Shear wave velocities were estimated up to 30 m depth. Average shear wave velocity (VS30) up to top 30m was also computed. It is observed that, VS in the range 400-800 m/s upto 10-15 m corresponding to weathered rock, followed by compact dolomite rock up to the depth of about 30 m with VS in the range 1200-1600 m/s. Some low velocity zones are also identified from these sections which represent shear zones.

Performance Improvement of Partially Silicon-on-Insulator Lateral Double-Diffused Metal–Oxide–Semiconductor Field-Effect Transistors Using Doping-Engineered Drift Region

In this paper, we investigate the characteristics of a drift region engineered lateral double-diffused metal–oxide–semiconductor field-effect transistor (LDMOSFET) based on partially silicon on insulator (PSOI) technology. The structure, which is called DEPSOI (drift region engineered PSOI), has a drift region with two different doping density levels. The structure only needs one additional fabrication mask, compared to the conventional power PSOI device. In the drift region, a new peak is formed in the lateral electric field distribution at the boundary between the drift areas, which leads to a flatter electric field profile and subsequently a higher breakdown voltage (BV) compared to those of a conventional device. The results show that the DEPSOI LDMOSFET has a BV which is about 64% more than that of an optimized conventional PSOI LDMOSFET with the same dimension. The use of two different doping density levels allows simultaneous optimization of different device parameters. Having one part of drift region with a higher doping density level leads to an improvement of the on-state resistance (Ron). Finally, DEPSOI LDMOSFET has a superior heat dissipation property than that of the conventional LDMOSFET structures. The effects of varying different physical parameters of the structure on the characteristics of the transistor are also studied.

Dune Landscape Rejuvenation by Intended Destabilisation in the Amsterdam Water Supply Dunes

In the Dutch coastal dunes, several projects have started in which aeolian activity is stimulated to enhance landscape rejuvenation by increasing aeolian erosion and deposition. The aim of these projects is to reverse vegetation succession and create opportunities for pioneer stages. In 1995, a drinking water extraction canal in the Amsterdam Water Supply Dunes was closed and the original landscape was restored. Since then, the development of the area was left to natural processes. This resulted in large-scale deflation structures and the development of sand drift areas. By means of air photographs, the changes in the landscape were studied. Initially, the sand drift area expanded, up to a maximum of 11 ha in 1999. In the following years, stabilisation of the surface by vegetation became more and more important. After 8 years of undisturbed development, half of the bare surface was still bare, and the active area was still 2.5 times larger than the stabilised area. But bare spots were scattered over the area, and the average size per spot decreased from 10 ha in 1995 to <1 ha in 2003. The percentage of surface covered by pioneer species was large (5 ha in 2003) and might result in increased stabilisation rates in future. Part of the stabilisation could be explained by meteorological conditions during the studied period. Part could be explained because the system is supply limited. Scale might be an important issue in the final success of remobilisation, as indicated by preliminary comparison to larger-scaled projects. Further comparisons are needed. After eight years, it is still too early to say whether large-scale destabilisation measures in the case of artificially fixed coastal dunes result in durable aeolian activity and landscape rejuvenation. However, even if the area will be stabilised within the next years, the landscape has many impulses for new ecological development. For the next decade, we need to continue our monitoring programs; meanwhile, experimentation with methods of reactivation should be conducted.

First estimates of regional (Allgäu, Germany) and global CH4 fluxes from wet colluvial margins of closed depressions in glacial drift areas

Abstract Agriculture is one of the major anthropogenic methane source. However, emission inventories of agricultural soils are rather uncertain. One reason for this is the existence of small areas of very high biogeochemical fluxes (‘hot spots’), which are not incorporated into soil maps. Here a procedure for an upscaling of one man-made ‘hot spot’ is presented. In hummocky ground moraines of temperate-humid climate (Allgau, Germany) erosion and subsequent sedimentation of topsoil material in wet footslope areas has led to very high emissions from depression margins (median annual flux=39 g CH 4 m −2 ). These areas make up 7% of the region studied according to a digital terrain analysis based on a DEM 50. GIS-based modelling showed their regional and global relevance to be a result of the (i) unit area source strength, (ii) relative acreage of depression margins in catchments of hummocky landscapes, and (iii) global dimension of hummocky landscapes with closed depressions. First conservative estimates yielded methane emissions of 1.1 Gg (regional, Allgau) and 2.5 Tg (global) from colluvial margins in similar landscapes, respectively.

Impact of insecticide drift on aphids and their parasitoids: residual toxicity, persistence and recolonisation

The effects of the insecticide Lannate ® 20 L on target and non-target organisms were studied in sprayed and drift areas of kohlrabi ( Brassica oleracea). The study comprised eight field plots (each 12.5 m×6 m), providing four replicates of a water control and the application with Lannate ® 20 L at 0.45 kg/ha. Each plot comprised a 4 m wide sprayed area and a 2 m wide “drift” area, left unsprayed. The parasitoid Aphidius colemani (Hymenoptera; Braconidae) and its host aphid Myzus persicae (Hemiptera; Aphididae) served as indicator organisms. The residual toxicity of Lannate ® 20 L to A. colemani and M. persicae was quantified in an exposure experiment. Plants were taken from the field at different time intervals following the insecticide treatment to expose test organisms to plant surfaces in the laboratory. Mortality rates of A. colemani were 94% on plants removed on the day of the application from the treated area and 79 and 69% on plants 0.6 and 2 m downwind from the treated area. No toxic effects on parasitoids were observed 4 days after treatment (a.t.). M. persicae were less susceptible to Lannate ® 20 L residues compared to A. colemani. M. persicae mortality was 46% on plants collected from the sprayed area on the day of the application and 5 and 8% on plants collected from the drift area. In addition, densities of aphids and aphid mummies in the treated and drift areas of field plots were assessed from 1 day pre-treatment to 14 days post-insecticide application. Spraying significantly decreased aphid densities, but the population built up again. Compared to the control, no effect was detected on aphid population densities in the drift area of field plots. Densities of mummies in the insecticide treated area of plots were lower compared to densities in the control from 1 day post-application. There was no effect on mummy densities in the drift area. Recolonisation of field plots following the insecticide treatment was estimated by the release of A. colemani. Since A. colemani is not indigenous in northern Germany it was possible to determine their dispersal into the crop by mummy collections. Recovery of A. colemani mummies was low.

Investigation of Herbaceous Species Adapted to Snowfence Areas

Decreases in biomass and cover, as well as changes in species composition have occurred on rangelands affected by snowdrifts behind 3.8 meter tall Wyoming type snowfences along Interstate 80 in southeast Wyoming. Within the state of Wyoming, government agencies are responsible for the mitigation of any adverse effects associated with snowfences. These agencies need information which may aid mitigation efforts. In this study, 13 grass species and 2 tillage treatments (till and no-till) were evaluated in the field on both drift and non-drift areas, to determine the potential of each for the revegetation of snowfence sites. Evaluation was based on foliar cover at the end of the first growing season and aboveground biomass production after the second growing season. The project included plantings on 2 different soil depth sites ( 50 cm) that were treated as 2 separate experiments. Results indicate that pubescent wheatgrass 'Luna' (Elytrigia intermedia [Host] Nevski), thick-spike wheatgrass 'Critana' (Elymus lanceolatus [Scribn. &J.G. Smith] Gould), and 2 varieties of slender wheatgrass 'Pryor' and 'San Luis' (Elymus trachycaulus [Link] Gould ex Shinners), were superior in cover and aboveground biomass production when planted in combination with tilled plots. Tufted hairgrass (Deschampsia caespitosa [L.] Beauv.) exhibited the least potential for cover and aboveground biomass production. DOI:10.2458/azu_jrm_v53i4_perryman

Investigation of herbaceous species adapted to snowfence areas

Decreases in biomass and cover, as well as changes in species composition have occurred on rangelands affected by snowdrifts behind 3.8 meter tall "Wyoming" type snowfences along Interstate 80 in southeast Wyoming. Within the state of Wyoming, government agencies are responsible for the mitigation of any adverse effects associated with snowfences. These agencies need information which may aid mitigation efforts. In this study, 13 grass species and 2 tillage treatments (till and no-till) were evaluated in the field on both drift and non-drift areas, to determine the potential of each for the revegetation of snowfence sites. Evaluation was based on foliar cover at the end of the first growing season and aboveground biomass production after the second growing season. The project included plantings on 2 different soil depth sites (&lt; 50 cm and &gt; 50 cm) that were treated as 2 separate experiments. Results indicate that pubescent wheatgrass 'Luna' (Elytrigia intermedia [Host] Nevski), thick-spike wheatgrass 'Critana' (Elymus lanceolatus [Scribn. J.G. Smith] Gould), and 2 varieties of slender wheatgrass 'Pryor' and 'San Luis' (Elymus trachycaulus [Link] Gould ex Shinners), were superior in cover and aboveground biomass production when planted in combination with tilled plots. Tufted hairgrass (Deschampsia caespitosa [L.] Beauv.) exhibited the least potential for cover and aboveground biomass production.

Late Quaternary stratigraphy and palaeoceanographic change in the northern Rockall Trough, North Atlantic Ocean

Abstract A series of six shallow gravity cores, taken from a variety of sedimentary settings in the northern Rockall Trough, have been analysed using microfossil and sedimentological techniques. Cores from sediment waves on the Barra Fan are interpreted as being sequences of hemipelagites, turbidites and hemiturbidites. Northeastern Rockall Trough cores, from slope apron, escarpment and sediment drift areas are interpreted as hemipelagites, with glaciomarine deposits interbedded with and overlain by muddy-silty and sandy contourites. The dinoflagellate cyst, planktonic foraminifera and nannofossil biostratigraphy reveals a four-fold deglaciation record, with a single long core from the Barra Fan seemingly containing all four divisions of the Late Glacial, Allerød-Bölling, Younger Dryas and Holocene intervals. The sedimentary record suggests that deglaciation in the North Atlantic Ocean was not a simple linear process but an irregular, non-linear series of rapid events characterized by sudden sea-surface temperature changes, and fluctuating bottom-current activity.

Three-Bimensional Geologic Mapping: A Basis for Hydrogeologic and Land-Use Evaluations

Development of practical mapping techniques to show the three-dimensional distribution of geologic materials directly and to specified depths has significantly improved the ease and accuracy of preparing interpretive maps. The continued development and use of hydrogeologic maps based on the terrain map can be of direct value. Their use will also improve many interpretive maps showing waste disposal and construction conditions and rating geologic conditions for other land uses. In most geologic and hydrogeologic settings, geologic maps based on the stack-unit and terrain concept can provide the regional hydrogeologic predictability necessary for evaluating aquifer conditions and paths of potential contaminant transport, and the general information necessary for regional planning of the development and management of water and other resources. The development of three-dimensional stack-unit and terrain maps in Illinois has focused specifically on the glaciated portions of the state; bedrock has been included in the mapping in thin drift areas. Because the same mapping concepts apply, there is reason to believe stack-unit maps and terrain maps can be constructed for most geologic settings. (TRRL)