Rising Water Table Research Articles

Rapid evolution of water resources in the Senegal delta

In recent decades major water developments have led to an agricultural transformation of the Senegal delta both in Senegal and Mauritania. This otherwise, semi-arid region of the Sahel band now has an abundant supply of freshwater all year round mostly used for irrigation and urban water supply, including for the capital cities of the two countries. Archives from the Landsat satellites and in-situ hydrographs were used in this paper to retrace and analyse the hydrological changes that have taken place in the region since the middle of the 20th century. The satellite archives indicate that the area covered by irrigation increased by one order of magnitude from 73km2 in 1973 to ~770km2 in 2010. The observed hydrological changes are complex, multi-faceted and often of great magnitude. If the water cycle was representative of natural conditions in the early 1980s, it is now representative of a heavily modified system controlled and impacted by human activities. The first hydraulic infrastructure was installed in 1947 to enable the Lake of Guiers to become the main water supply for Dakar. Two large dams were built on the Senegal River in the mid-1980s that modified the hydrological regime of the river by 1) preventing seawater intrusion, 2) raising the stage of the river and of Lake of Guiers and 3) moderating floods. Another recent hydrological change in the delta was the opening of river mouth in 2003, which has led to a reduction of the average water level while increasing the semi-diurnal tidal wave between the river mouth and Diama. Each phase of these river regime changes and each step of the irrigation expansion are expressed in localised changes in the physical groundwater system. Increasingly, the retroaction from the shallow aquifer systems is observed as a rise of the saline water table. This poses a threat to the environmental and agricultural value of the region, and the salinization of the soils. Mitigating actions for this threat are currently being envisaged by the authorities.

Sources and seasonal variation of coliform bacteria abundance in groundwater around the slopes of Mount Meru, Arusha, Tanzania

The quality of the groundwater along the slopes of Mount Meru, Tanzania, is poorly understood. Water access and sanitation practices may pose health risks to communities. This study was undertaken to assess the sources, abundance and seasonal variation of coliform bacteria in groundwater and factors contributing to such variations along slopes of Mount Meru, Tanzania. Water samples collected from 67 randomly selected water sources (springs, shallow wells which ranged from 4 to 35m deep and Boreholes above 40m deep) during dry and wet seasons were analysed for total coliform (TC), faecal coliform (FC), Escherichia coli (E. coli) and faecal streptococci (FS), using the membrane filtration method. The fraction of springs and shallow wells contaminated was generally higher compared to the fraction of boreholes. The highest TC, FC, E. coli and FS counts were significantly higher (p < 0.05) during the wet than the dry season owing to rising of water table and leaching during rainy season. Water sources that were located within 10m of pit latrines had the highest coliform counts relative to those located beyond 10m. Similarly, the highest coliform counts were observed in all shallow wells that (i) had low well head above the ground, (ii) were not covered, (iii) had casing materials which were not concrete and (iv) utilised traditional pumping (bucket/pulley) systems. This was due to contaminated storm water access, inoculation of microbes by exposed buckets and inefficiency of the casing material. Furthermore, the counts decreased with depths of boreholes and shallow wells during the two seasons probably due to retention and die-off. It is recommended that groundwater in this area be treated against coliform contamination prior to utilisation as portable water.

Effect of long duration rainstorm on stability of Red-clay slopes

Slope stability issue in red clay slopes during rainfall is one among the serious geoenvironmental disasters in China. In order to investigate the effect of long duration rainstorm on red-clay slopes, studies were conducted using Geostudio 2012. Five different rainfall-durations were applied to the slope and the results of coupled and uncoupled calculation modes were compared. Results show that pore water pressure increased due to the dissipation of matric suctions and rise in water table during the rainfall period with the longer the rainfall duration, the larger the pore water pressure. The rate of change of pore water pressure was largest at rainfall durations of 4 days, among all the duration conditions considered for this study. After short duration rainstorms, a settlement of the surface of the slope was observed. However, in long duration rainstorms, the slope surface swelled in a non-uniform manner with the head of the slope experiencing the greatest expansion. Factor of safety exhibited a hysteresis during the calculation process, which was similar in trend with the pore water pressure as well, and it showed some amplitude during the calculation steps under the coupled calculation analysis as a result of the deformation and seepage force affecting each other on the performance of slope, especially for the slope stability.

Control of cave levels in Kanaan, Kassarat and Jeita karst systems (Central Mount Lebanon, Lebanon)

Mount Lebanon is a mountainous Mediterranean karst ridge, consisting of high plateaus reaching 3,088 m altitude and entrenched by deep valleys. Fluvial drainage systems run on a steep gradient and reach the Mediterranean Sea coast in less than 30 km distance. In Central Mount Lebanon, the downstream parts of Antelias and Kalb valleys host the Kanaan cave (160 m), the Kassarat cave (4.6 km) and the Jeita cave (10.05 km), whose subterranean rivers are connected to the karst springs located close to the contact between the Cretaceous aqui- clude and the Jurassic karst aquifer. The area thus comprises a dammed Jurassic aquifer in which all the studied cave levels developed at certain altitudes. A geomorphological study performed by speleological and geomorphological surveys and completed by analyses of cave sediments allowed the formulation of a first evolutionary framework of the karst system. Several features suggest a long-term and multi-stage evolution of the karst in both Antelias and Kalb valleys. The horizontal caves develop between 60 and 160 m a. s. l. and constitute water table caves in a steeply dipping structure (Mount Lebanon's western fold). These cave levels are part of an ancient system that developed near the water table controlled by the position of the aquiclude and correspond to the base level of a past fluvial network. An important phase of base level cave development is documented in the relict passages above 90 m a. s. l. Speleogenetic features between 90 and 160 m developed in a phreatic environment where paragenesis or per ascensum erosion processes occurred during base level rise. Epiphreatic features were identified at 60–70 m in Kassarat and Jeita caves. Typical morphological features such as horizontal solution passages and solution notches suggest a phase of stillstand of the base-level. The evolution of the water table level from a paragenetic rise above 90 m to a continuous lowering below 90 m and with a temporary stillstand phase at 70–60 m, is related to the fluvial base-level evolution. Preliminar chronological constraints for the evolution of the karst system are discussed based on U/Th dating of speleothems and cave levels (90–160 and 60–70 m) and their relationship with the altitude of the low-gradient surfaces. The cave levels between 90 and 160 m are related to a water table rise that caused an alluviation process at the river's mouth probably during the Pliocene transgression phase of the Mediterranean Sea (PHS). Abandoning of the upper cave levels (90–160 and 60–70 m) is the result of a continuous lowering of the water table related to fluvial incision. The lowering of the water table level below 90 m is mainly related to the fluvial incision of the acquiclude in a high geodynamic context (Mount Lebanon uplift) during the Pleistocene.

Generic 3D interpolation of Holocene base‐level rise and provision of accommodation space, developed for the Netherlands coastal plain and infilled palaeovalleys

AbstractWe present an interpolation model that describes Holocene groundwater level rise and the creation of accommodation space in 3D in the Rhine‐Meuse delta – the Netherlands. The model area (ca. 12 400 km2) covers two palaeovalleys of Late Pleistocene age (each 30 km wide) and the overlying Holocene deposits of the Rhine‐Meuse delta, the Holland coastal plain, and the Zuiderzee former lagoon. Water table rise is modelled from 10 800 to 1000 cal. BP, making use of age‐depth relations based on 384 basal peat index points, and producing output in the form of stacked palaeo groundwater surfaces, groundwater age‐depth curves, and voxel sets. These products allow to resolve (i) regional change and variations of inland water table slopes, (ii) spatial differences in the timing and pacing of transgression, and (iii) analysis of interplay of coastal, fluvial and subsidence controls on the provision of accommodation space. The interpolation model is a multi‐parameter trend function, to which a 3D‐kriging procedure of the residuals is added. This split design deploys a generic approach for modelling provision of accommodation space in deltas and coastal lowlands, aiming to work both in areas of intermediate data availability and in the most data‐rich environments. Major provision of accommodation space occurred from 8500 cal BP onwards, but a different evolution occurred in each of the two palaeovalleys. In the northern valley, creation of accommodation space began to stall at 7500 cal BP, while in the southern valley provision of new accommodation space in considerable quantities continued longer. The latter is due to the floodplain gradient that was maintained by the Rhine, which distinguishes the fluvial deltaic environment from the rest of the back‐barrier coastal plain. The interpolation results allow advanced mapping and investigation of apparent spatial differences in Holocene aggradation in larger coastal sedimentary systems. Furthermore, they provide a means to generate first‐order age information with centennial precision for 3D geological subsurface models of Holocene deltas and valley fills. As such, the interpolation is of use in studies into past and present land subsidence and into low land sedimentation.

Debris-flow events at Mt Mangart, Slovenia

In November 2000, following significant rainfall of long duration but relatively low intensity, a sequence of mass movements occurred on the slopes of Mt Mangart in Slovenia. The initial mass movement involved a relatively dry debris flow triggered by a rising water table. The debris-flow deposits filled the local valley, blocking the stream. The deposits gradually became saturated and 2 days later resulted in a secondary (wet) debris flow. This second event was much more mobile, travelling rapidly through steep terrain and leading to the destruction or damage of 29 buildings in the village of Log pod Mangartom and seven fatalities.

Optimal Allocation of Resources for Increasing Farm Revenue under Hydrological Uncertainty

The formulation and application of two optimization models is presented in this study. The models were used to maximize the net farm revenue of an irrigated area located in northwest India by optimally allocating the available water and land resources. In order to moderate the rising water table issues, a ground water component was introduced in the model, while still ensuring optimal resources allocation. Results of the model indicates a reduction in barley, gram, mustard, and rice production area while at the same time an increase in sugarcane, millets, wheat, and cotton cultivation areas under optimal conditions. The ground water exploitation has increased in the model allocation, which consecutively moderated the rising water table problems. The model allocations has resulted in more than 31 % increase in net farm revenue. The proposed models can be employed as a dependable tool for making the decisions at local and regional levels and are capable of solving the rising water table issues of irrigated areas. The formulations proposed in this study are simple and can be employed anywhere for capitalizing on the farm revenue by moderating the water resources problems. The model constraints, though, be different considering the quality and quantity aspects of different water sources.

Facies architecture and stratigraphic evolution of aeolian dune and interdune deposits, Permian Caldeirão Member (Santa Brígida Formation), Brazil

The Permian Caldeirão Member (Santa Brígida Formation), located in the Tucano Central Basin, northeast region of Brazil, is characterized by a sandstone succession of aeolian origin that comprises the preserved deposits of dunes and interdunes. Grainflow and translatent wind-ripple strata, and frequent presence of reactivation surface, compose the cross-bedding of crescent aeolian dune deposits. The aeolian cross-strata show a mean dip toward the ENE. In places, interlayered with dune cross-beds, occur interdune units composed of facies indicative of dry, damp and wet condition of the substrate, suggesting spatial and/or temporal variations in the moisture content of the interdune accumulation surface. The presence of NNW current ripple cross-lamination in wet interdune areas indicates streamflows confined to interdune corridors and oriented perpendicular to aeolian transport direction. Lenses of damp and wet interdune strata exhibit mainly interdigitated and transitional relationships with the toe-sets of overlying aeolian dune units in sections parallel to aeolian transport, indicating that dune migration was contemporaneous with accumulation in adjacent interdunes. Lateral variations in the preserved thickness of the interdune units and the associated rare occurrence of abrupt and erosive contacts between interdune and overlying dune sets, suggest temporal variations in the angle of dune and interdune climb that may be related to high-frequency changes in water table position. Four stratigraphic intervals in the Caldeirão Member can be identified, two intervals showing cross-bedding of aeolian dunes without wet interdune areas and two intervals exhibiting aeolian dunes separated by wet interdune areas, marking the transition between dry aeolian systems (Intervals I and III) and wet aeolian systems (Intervals II and IV). The temporal alternations between dry and wet aeolian systems reflect changes in the availability of dry sand and/or the rate in the water table rise, possibly controlled by orbitally-driven climatic fluctuations.

A coupled model simulation assessment of shallow water-table rise in a Saudi Arabian coastal city

The problem of a rising shallow water-table level in the coastal city of Dammam in eastern Saudi Arabia was investigated through data collection, analysis, and numerical modelling. The research focused on applying a coupled model that considers flow in both the saturated and unsaturated zones. Geophysical and hydrogeological data were collected through field investigations, and various analyses of this data were performed. A computer simulation model of shallow groundwater flow was developed and applied to define the recharge sources. The generalised HYDRUS and MODFLOW modelling packages were coupled to simulate the vadose zone and saturated zone, respectively. The calibrated coupled groundwater model was used to determine the contributions of each possible recharge source, and thus to identify the major causes of the rise in the water table. The shallow water-table rise was found to be a serious threat to the present and future development of this large city.

Dynamic performance of high-speed railway formation with the rise of water table

This paper presents an experimental study on the influences of water table and train speeds on the dynamic performance of high-speed railway formation using a full-scale physical model testing apparatus. Stationary cyclic loading tests were first conducted to assess the fundamental dynamic performance of railway formation caused by increasing groundwater table. Resilient deformation increased significantly when water table rose from the subsoil bottom to the subgrade surface, and the resonant frequency of the track-formation system decreased from 16Hz to 12Hz. Then moving loading tests simulating train's passages were performed to reveal the dynamic responses of railway formation at train speeds of 5–360km/h, such as the resilient deformation, dynamic soil stress and dynamic pore water pressure. Test results of two kinds of subgrade conditions were presented and compared, i.e., the design condition with the optimum subgrade moisture content and the extreme condition of the submerged subgrade. Combined with the amplification effect of increasing train speeds, the dynamic responses developed faster and larger due to water table rising. The contact pressure distribution under the track structure exhibited the shape of concave parabola for the optimum subgrade, while the distribution pattern presented the shape of letter “W” for the submerged subgrade as the soils around the edges entered into the plastic state. Finally, determination of the subgrade thickness for the design and extreme conditions was discussed, and the design code underestimated the subgrade thickness for the extreme situation in high-speed railways.

Peat decomposition – shaping factors, significance in environmental studies and methods of determination; a literature review

Abstract A review of literature data on the degree of peat decomposition – an important parameter that yields data on environmental conditions during the peat-forming process, i.e., humidity of the mire surface, is presented. A decrease in the rate of peat decomposition indicates a rise of the ground water table. In the case of bogs, which receive exclusively atmospheric (meteoric) water, data on changes in the wetness of past mire surfaces could even be treated as data on past climates. Different factors shaping the process of peat decomposition are also discussed, such as humidity of the substratum and climatic conditions, as well as the chemical composition of peat-forming plants. Methods for the determination of the degree of peat decomposition are also outlined, maintaining the division into field and laboratory analyses. Among the latter are methods based on physical and chemical features of peat and microscopic methods. Comparisons of results obtained by different methods can occasionally be difficult, which may be ascribed to different experience of researchers or the chemically undefined nature of many analyses of humification.

Detrital cave sediments record Late Quaternary hydrologic and climatic variability in northwestern Florida, USA

Detrital sediment in Florida's (USA) submerged cave systems may preserve records of regional climate and hydrologic variability. However, the basic sedimentology, mineralogy, stratigraphic variability, and emplacement history of the successions in Florida's submerged caves remains poorly understood. Here we present stratigraphic, mineralogical, and elemental data on sediment cores from two phreatic cave systems in northwestern Florida (USA), on the Dougherty Karst Plain: Hole in the Wall Cave (HITW) and Twin Cave. Water flowing through these caves is subsurface flow in the Apalachicola River drainage basin, and the caves are located just downstream from Jackson Blue (1st magnitude spring, >2.8m3s−1 discharge). Sedimentation in these caves is dominated by three primary sedimentary styles: (i) ferromanganese deposits dominate the basal recovered stratigraphy, which pass upsection into (ii) poorly sorted carbonate sediment, and finally into (iii) fine-grained organic matter (gyttja) deposits. Resolving the emplacement history of the lower stratigraphic units was hampered by a lack of suitable material for radiocarbon dating, but the upper organic-rich deposits have a punctuated depositional history beginning in the earliest Holocene. For example, gyttja primarily accumulated in HITW and Twin Caves from ~5500 to 3500calyr. BP, which coincides with regional evidence for water-table rise of the Upper Floridian Aquifer associated with relative sea-level rise in the Gulf of Mexico, and evidence for invigorated drainage through the Apalachicola River drainage basin. Gyttja sediments were also deposited in one of the caves during the Bølling/Allerød climate oscillation. Biologically, these results indicate that some Floridian aquatic cave (stygobitic) ecosystems presently receive minimal organic matter supply in comparison to prehistoric intervals. The pre-Holocene poorly sorted carbonate sediment contains abundant invertebrate fossils, and likely documents a period of enhanced limestone dissolution and cave formation (speleogenesis) during lower paleo water levels. Further work is still required to (a) determine whether precipitation of the ferromanganese deposits is inorganically or biologically mediated, (b) temporally constrain the emplacement history of the primary sedimentary styles, and (c) determine the full geographic extent of these sedimentary signals. However, these preliminary observations suggest that sedimentation in the inland underwater caves of northwestern Florida is related to Quaternary-scale hydrographic variability in the Apalachicola River drainage basin in response to broader ocean and atmospheric forcing.

Analysis of groundwater-level response to rainfall and estimation of annual recharge in fractured hard rock aquifers, NW Ireland

Summary Despite fractured hard rock aquifers underlying over 65% of Ireland, knowledge of key processes controlling groundwater recharge in these bedrock systems is inadequately constrained. In this study, we examined 19 groundwater-level hydrographs from two Irish hillslope sites underlain by hard rock aquifers. Water-level time-series in clustered monitoring wells completed at the subsoil, soil/bedrock interface, shallow and deep bedrocks were continuously monitored hourly over two hydrological years. Correlation methods were applied to investigate groundwater-level response to rainfall, as well as its seasonal variations. The results reveal that the direct groundwater recharge to the shallow and deep bedrocks on hillslope is very limited. Water-level variations within these geological units are likely dominated by slow flow rock matrix storage. The rapid responses to rainfall (⩽2 h) with little seasonal variations were observed to the monitoring wells installed at the subsoil and soil/bedrock interface, as well as those in the shallow or deep bedrocks at the base of the hillslope. This suggests that the direct recharge takes place within these units. An automated time-series procedure using the water-table fluctuation method was developed to estimate groundwater recharge from the water-level and rainfall data. Results show the annual recharge rates of 42–197 mm/yr in the subsoil and soil/bedrock interface, which represent 4–19% of the annual rainfall. Statistical analysis of the relationship between the rainfall intensity and water-table rise reveal that the low rainfall intensity group (⩽1 mm/h) has greater impact on the groundwater recharge rate than other groups (>1 mm/h). This study shows that the combination of the time-series analysis and the water-table fluctuation method could be an useful approach to investigate groundwater recharge in fractured hard rock aquifers in Ireland.

Rainfall seasonality on landslide probability: a modelling approach

Precipitation is one of the main landslides triggering factors because the amount of infiltrated water into the ground causes changes in pore pressure due to the decrease in suction or the rising water table level. In this paper we estimated the return period of landslides from a rainfall stochastic behavior. Using rainfall intensity and duration probability density functions (pdf) and Philip’s infiltration model, the pdf of water infiltrated volume into the soil was obtained. Then, assuming the soil reaches saturation, the pdf of depth wetting front (zw) was obtained. Finally, with zw and the Mohr-Coulomb rupture criteria, the pdf of the Factor of Safety (FS) was determined. Subsequently, landslide occurrence was analyzed under different hydroclimatic scenarios, such as dry and wet seasons and El Nino Southern Oscillation (ENSO) phases. The occurrence of shallow landslides depends more on intensity storm than duration storm, and they are more likely to happen during La Nina phase than during El Nino phase because both storm duration and storm intensity tend to increase.

Dynamics of spring water table rise of drainless lakes (exemplified by Lake Krasilovskoe, Altai krai)

Dynamics of spring water table rise of drainless lakes (exemplified by Lake Krasilovskoe, Altai krai)

Sequence stratigraphy of fluvially-dominated strata of the Mid-Late Pennsylvanian Conemaugh Formation, Central Appalachian Basin

Sequence stratigraphic analysis of nonmarine, fluvially-dominated strata is particularly challenging compared to paralic and marine sequences due to rapid facies changes and limited lateral continuity of key beds. The Conemaugh Formation of central West Virginia is a prime example of this type of stratigraphic interval. This study describes the stratigraphy and sedimentary facies from 68 outcrops in the lower 100m of the Mid-Late Pennsylvanian, nonmarine Conemaugh Formation in this area. Facies identified include 1) fluvial–upper estuarine channel sandstones, 2) crevasse splay channel and sheet sandstones, 3) lacustrine shale, mudstone, and claystone, 4) lacustrine/palustrine limestone, 5) paludal coal and carbonaceous shale, and 6) hackly mudstone and claystone paleosols.Mature, polygenetic, high-chroma calcic vertisols and calcisols are the regionally developed interfluvial sequence boundaries (IFSBs) of seven fourth-order sequences (major cyclothems) between the Upper Freeport and Harlem coal horizons. Initial paleosol development occurred under well-drained conditions and strongly seasonal, semiarid–arid climate approaching and during glacial maxima at a time of minimal accommodation space on the interfluves. Subsequent rising water table associated with rising base level occurred as interglacial sea level rose and the climate became less seasonal and more humid. This initially led to deposition of thin, carbonaceous mud and peat followed by lacustrine and palustrine limestones. The presence of spirorbid microconchids indicates that the lakes were at least intermittently connected to the sea, which reached to within 50–80km of all outcrops in the study during five transgressions. The tops of these limestones represent maximum flooding surfaces. They are overlain by coarsening–upward lake-fill sequences formed during high accommodation on the interfluves during the HST. A nonmarine sequence stratigraphic model and a polygenetic paleosol model are proposed for the Conemaugh in central West Virginia. This study underscores the importance of recognizing regionally developed IFSB paleosols and microconchid limestones in correlation and sequence stratigraphic analysis.

The City of Rome and its groundwater: from critical issues, to urban resilience opportunities

This paper emphasizes the importance of groundwater resources of Rome with regard to its protection, and the associated issues. There are different tipologies of interference between human presence and groundwater in the city, ranging from the presence of water circulating inside the thick layers of anthropogenic deposits, the frequent contamination of groundwater, the presence of mining activities, the presence of archaeological heritage in underground or in low areas affected by flooding also induced by water table rising. Despite the various issues that are found, the knowledge of groundwater resources of Rome can be an important starting point to enhance its protection s and take advantage of the related countless benefits also aim to increase urban resilience.

Modeling and assessing field irrigation water use in a canal system of Hetao, upper Yellow River basin: Application to maize, sunflower and watermelon

Water saving in irrigation is a key issue in the upper Yellow River basin. Excessive irrigation leads to water waste, water table rising and increased salinity. Land fragmentation associated with a large dispersion of crops adds to the agro-hydrological complexity of the irrigation system. The model HYDRUS-1D, coupled with the FAO-56 dual crop coefficient approach (dualKc), was applied to simulate the water and salt movement processes. Field experiments were conducted for maize, sunflower and watermelon crops in the command area of a typical irrigation canal system in Hetao Irrigation District during 2012 and 2013. The model was calibrated and validated in three crop fields using two-year experimental data. Simulations of soil moisture, salinity concentration and crop yield fitted well with the observations. The irrigation water use was then evaluated and results showed that large amounts of irrigation water percolated due to over-irrigation but their reuse through capillary rise was also quite large. That reuse was facilitated by the dispersion of crops throughout largely fragmented field, thus with fields reusing water percolated from nearby areas due to the rapid lateral migration of groundwater. Beneficial water use could be improved when taking this aspect into account, which was not considered in previous researches. The non-beneficial evaporation and salt accumulation into the root zone were found to significantly increase during non-growth periods due to the shallow water tables. It could be concluded that when applying water saving measures, close attention should be paid to cropping pattern distribution and groundwater control in association with irrigation scheduling and technique improvement.

Sinkholes, collapse structures and large landslides in an active salt dome submerged by a reservoir: The unique case of the Ambal ridge in the Karun River, Zagros Mountains, Iran

Ambal ridge, covering 4km2, is a salt pillow of Gachsaran Formation with significant salt exposures in direct contact with the Karun River, Zagros Mountains. The highly cavernous salt dome is currently being flooded by the Gotvand Reservoir, second largest in Iran. Geomorphic evidence, including the sharp deflection of the Karun River and defeated streams indicate that Ambal is an active halokinetic structure, probably driven by erosional unloading. Around 30% of the salt dome is affected by large landslides up to ca. 50×106m3 in volume. Slope oversteepening related to fluvial erosion and halokinetic rise seems to be the main controlling factor. A total of 693 sinkholes have been inventoried (170sinkholes/km2), for which a scaling relationship has been produced. The depressions occur preferentially along a belt with a high degree of clustering. This spatial distribution is controlled by the proximity to the river, slope gradient and halite content in the bedrock. A large compound depression whose bottom lies below the normal maximum level of the reservoir will likely be flooded by water table rise forming a lake. The impoundment of the reservoir has induced peculiar collapse structures 220–280m across, expressed by systems of arcuate fissures and scarps. Rapid subsurface salt dissolution is expected to generate and reactivate a large number of sinkholes and may reactivate landslides with a significant vertical component due to lack of basal support.

Effect of Geosynthetic on the Performance of Road Embankment over Sabkha Soils in Algeria: Case Study

This paper focuses on the construction technique of road embankment which crosses a section of about 11 km on sabkha soils of Chott El Hodna in Algeria. Due to the poor bearing capacity of sabkha surface and the rising water table over the surface, serious difficulties were encountered during the investigation of the subsurface soil and the construction of the first embankment layers. In this construction site, the use of basal geosynthetic layer to maintain the performance of embankment was found to have relevant reinforcing effect by increasing the soil bearing capacity to allow safe construction of the first layers and improving the compaction quality. Based on the in situ observations and the geotechnical investigation, numerical simulations were performed using the software PLAXIS. The results have shown the contribution conditions of geosynthetics to improve the bearing capacity of sabkha soils.