Alluvial Lowland Research Articles

Evaluation of aquifer recharge and vulnerability in an alluvial lowland using environmental tracers

A multi-layered aquifer system (eastern Po plain, northern Italy) was investigated by means of isotopic data, with the goal of quantifying groundwater recharge from different sources and assessing the intrinsic vulnerability of aquifers to surface sources of contamination. The geology of the area is based on a stratigraphic alternation of several sandy aquifers and silty–clayey aquitards, down to a maximum depth of 200 m b.g.s. Water isotopes (δ18O, δ2H), and hydrochemical analyses were performed on groundwater samples collected from a regional network of 70 boreholes distributed on an area of almost 2000 km2. In addition to the regional sampling, detailed vertical isotopic profiling was performed in one location by means of groundwater and sediment samples collected through the whole sequence of aquifers and aquitards. Water isotopes indicated mixing from different sources of recharge (i.e., vertical recharge, Po river, deeper aquifers). Mixing calculations were used to quantify the contributions to the aquifers from the different sources. The vertical profiling allowed for integrating and validating the interpretations at a regional scale. The recharge pattern defined for the different aquifers was translated into an index of hydrogeologic interconnections with the surface, which represents a physically based proxy of the intrinsic vulnerability of the aquifers to surficial sources of contamination. The investigated setting can be considered to be representative of many other anthropized and groundwater demanding plain settings around the world. Thus, the proposed method represents a valuable approach for such settings both for recharge quantification (e.g., to be used as input for numerical modeling) and for a physically based assessment of the intrinsic vulnerability.

沖積低地の過去を知る—沖積低地研究をどう始めたか—

学部生時代の筆者は沖積低地に関して空中写真判読によって地形分類図を作成したり，ハンドボーリング調査などを経験していた．本格的に研究を始めた博士課程では，まず沖積低地の地形発達や海水準変動などの第四紀の環境変動に関する研究の流れをしっかり理解するために1850年代までさかのぼって関連文献を収集・整理し，研究の発展・展開を把握することにつとめた．その頃始めた津軽平野の調査の際に，埋没林を見つけて短報に投稿したのが最初の第四紀学の論文であった．さらに，珪藻分析を取り入れて沖積層の時空間的な変化を検討し，平野の地形発達史を明らかにした．その後，多摩川低地，濃尾平野等に関する論文を発展させて日本の沖積低地の地形発達に関する研究をまとめた．その頃，ガンジスデルタで調査を行う機会を得て，低地地形の特性を明らかにするとともに，機械式ボーリングを実施してサンプルを採取・分析するなどして，ガンジスデルタの地形形成を論じた．

Seismic Performance of Industrial Sheds and Liquefaction Effects During May 2012 Emilia Earthquakes Sequence in Northern Italy

On May 20, 2012 at 2:03 UTC, a Mw 6.1 earthquake occurred in Emilia Region of Northern Italy. The event was preceded by a Ml 4.1 foreshock on May 19, 2012 at 23:13 UTC, and followed by several aftershocks, twenty of them with a magnitude Mw greater than 4. The epicentral area of the seismic sequence covers alluvial lowland that is occupied by both agricultural and urbanized areas. Liquefaction effects were observed in several villages on the west side of Ferrara which were built upon former river beds such as the Reno River. The Emilia seismic sequence resulted in 27 casualties, several of whom were among the workers in the factories that collapsed during working hours, and there was extensive damage to monuments, public buildings, industrial sites and private homes. Almost no municipalities hit by 2012 earthquake were classified as seismic area before 2003; therefore, most of the existing structures had been designed without taking in account the seismic actions. The main aims of MCEER field mission was to document the emergency response and the most common damage mechanisms of industrial sheds during Emilia earthquake sequence which are shown and discussed in detail.

Hydraulic back-flood model for the archaeological stratigraphy of the Connecticut River Alluvial Lowland, central Connecticut, USA

State-mandated archaeological investigations associated with urban renewal in downtown Hartford led to the development of a mechanistic model for Holocene floodplain sedimentation in central Connecticut. Our model is based on: historic flood hydrometeorology and geomorphologic mapping; the lithologic, magnetic, pollen, and archaeological stratigraphy exposed in sixteen deep boreholes and 24 hydraulic push cores; the chronology provided by sixteen AMS radiocarbon ages, and diagnostic historic artifacts ranging from 10,030 cal BP to the present. We conclude that the alluvial stratigraphy in this part of the lowland resulted from bottom-up changes in hydraulic ponding at a bedrock outlet, rather than from top-down responses of the watershed to changes in climate, vegetation or human activity. Our model provides a geologically based time-space framework for the distribution of known archaeological sites, and carries implications for future research.

海津正倫編：沖積低地の地形環境学

海津正倫編：沖積低地の地形環境学

The May 2012 Emilia (Italy) earthquakes: preliminary interpretations on the seismogenic source and the origin of the coseismic ground effects

<p>On May 20, 2012, a Ml 5.9 earthquake (T1) occurred in the Emilia-Romagna Region of northern Italy. This was preceded by a Ml 4.1 foreshock on May 19, 2012, and followed by several aftershocks, including two Ml 5.1 events, both on the same day. On May 29, 2012, a second strong event of Ml 5.8 (T2) hit the same region, with its epicenter ca. 12 km to the WSW of the first mainshock, T1. The epicentral area of the seismic sequence covers an alluvial lowland that is occupied by both agricultural and urbanized areas, and there were 17 casualties and about 14,000 people left homeless. […] In the present study, we provide a preliminary model of the seismogenic source(s) responsible for the two mainshocks, by comparing the seismic reflection profile interpretation with the available seismological and interferometric data. Furthermore, we show the coseismic ground effects that were observed in the epicentral area during two field survey campaigns: the first conducted after the May 20, 2012, event and the second soon after the May 29, 2012, earthquake, when several sites were revisited to observe the occurrence of newly formed or 're-activated' liquefaction features. Hence, we discuss the origin and location of the coseismic features observed in the context of the local geological–geomorphological setting and with respect to the epicentral distance. Finally, we provide our interpretation for the question: "Why did the mainshock ruptures not break the surface?" […]</p><p><strong> </strong></p> <p><strong> </strong></p>

Influence of snow on near-surface ground temperatures in upland and alluvial environments of the outer Mackenzie Delta, Northwest Territories1This article is one of a series of papers published in this CJES Special Issue on the theme of Fundamental and applied research on permafrost in Canada.

Relations between snow cover, active-layer thickness, and near-surface ground temperatures were determined in 2005–2009 for a diverse range of alluvial and upland settings in the outer Mackenzie Delta. Here, the snow cover developed primarily by wind redistribution, with its spatial variation controlled by topography in uplands and vegetation height in alluvial lowlands. Snow cover was the primary influence on freeze-back duration and the mean annual temperature at the top of permafrost (TTOP), with the difference in median TTOP between alluvial (–3.7 °C) and upland (–6.1 °C) settings related to the greater snow depth and soil moisture in the alluvial plain. The active layer was generally deeper in the wet alluvial lowlands, where the average duration of active-layer freeze back (101 days) was nearly double the time taken in the well-drained uplands (55 days). The surface offset (ΔTS; up to 11 °C) dominated the difference between annual mean air temperature (AMAT) and TTOP (ΔT). In alluvial terrain, ΔTS varied with snow depth, but in the uplands, ΔTS was more consistent from site to site. The small thermal offset (<2 °C) was slightly greater in alluvial terrain than in the uplands. The overall range in ΔT (2–10 °C) led to a range during the study of 7.2 °C in TTOP at the sites. The range in AMAT was 1.3 °C but up to 1.7 °C in TTOP at any one site. Permafrost was well established throughout the area except adjacent to channels where TTOP was close to 0 °C.

Woodland Hypothesis for Devonian Tetrapod Evolution

The rarity of Devonian tetrapods and the absence of tetrapods during the first 14 million years of the Mississippian (Romer’s Gap) have inspired hypotheses of fish-tetrapod evolutionary transition as an escape from difficult habitats such as deserts or stagnant waters. These hypotheses and Romer’s Gap are tested here using depth to calcic horizon in paleosols of the northern Appalachians as a proxy for precipitation and vegetation changes during the Devonian and Mississippian. All tetrapod bones and trackways in this region, as well as fossil tree remains, were found at times of high precipitation (indicated by deep calcic paleosols), when subhumid woodlands expanded at the expense of semiarid shrublands in alluvial lowlands. No tetrapods or tree fossils were found in abundant paleosols with the shallow calcic horizons of aridland soils. The mean annual precipitation requirement of Devonian-Mississippian tetrapods and trees was at least mm. Global distribution of prototetrapods and aquatic tetrapods also shows that they lived earliest (Eifelian) in coastal lagoon or estuary margin soils of humid regions rather than in aridlands or intertidal flats. Tetrapods later spread to a variety of habitats, but continued preference for noncalcareous soils of woodlands and forests may explain Romer’s Gap as a preservational artifact. A woodland hypothesis of tetrapod evolution is presented here: limbs and necks were selected for by scavenging and hunting in shallow-flooded woodlands and oxbow lakes during a unique period in Earth history, after evolution of flood-ponding trees and before effective terrestrial predator resistance.

Hydrological and chemical budgets of a mire pool formed on alluvial lowland of Hokkaido, northern Japan

► Surface water inflow and surface water outflow dominate the hydrological budget of the pool. ► Total phosphorus is supplied mostly by groundwater seepage through the pool bottom. ► Total nitrogen and Ca 2+ are supplied by groundwater seepage and surface water inflow. ► Water and Ca 2+ fluxes are much greater than those of North American mire pools. ► We characterized the budgets of mire pools formed on alluvial lowlands in northern Japan. Mire pools – permanently water-filled depressions on peatlands – provide important habitats for myriad organisms. Recently, water balance change and eutrophication resulting from agricultural development are increasingly evident in mire pools of alluvial lowlands. Conservation of mire pool hydrochemistry is necessary. We investigated the hydrological and chemical budgets of a pristine mire pool, Akanuma Pool (95,280 m 2 area; 1.8 m mean depth), located in Kushiro Mire in Hokkaido, northern Japan, during its ice-free period (April–November) in 2007–2008. Thereby we elucidated the hydrochemical characteristics of mire pools formed on alluvial lowlands. Surface water inflow and surface water outflow dominated the hydrological budget, respectively representing 18.3 and 20.2 mm day −1 . Groundwater seepage through the pool bottom and surface water inflow mainly supplied the lake water with total nitrogen and Ca 2+ . Total phosphorus was supplied mostly by groundwater seepage through the bottom. These chemical constituents were run off from the pool mostly by surface water outflow. The input and output fluxes of water were 16–20 times greater than those of North American mire pools because of Hokkaido’s higher values of precipitation minus evapotranspiration ( P – ET ). Moreover, the Ca 2+ input into the Akanuma Pool was several times greater than those reported from North American studies. Alluvial mineral soil under the peat layer supplied large amounts of nutrients and mineral ions including Ca 2+ . These results demonstrate that Hokkaido mire pools’ hydrochemical characteristics differ greatly from those of pools in North America. Furthermore, each hydrological budget component maintained a constant fraction throughout the two year study period, although the absolute flow rate varied concomitantly with the precipitation level. Maintaining this budget stability is important for the conservation of mire pool hydrochemistry.

Did the flowering of the La Tolita culture 3000 BP result from a natural disaster?

The La Tolita site appeared on the Pacific coast of northern Ecuador around 3000 BP, and its culture quickly spread throughout the interior alluvial plain of mangrove and thick rainforest vegetation up to an elevation of 2000m along the Andean slopes. New geomorphic evidence shows that the flowering of the La Tolita culture could have followed a natural disaster that opened a new waterway, which facilitated communication with gold bearing areas and Andean communities landward. The La Tolita area is located in the Esmeraldas-Tumaco seismic zone, one of the most active on earth. The channel avulsion is correlated with active fault motion in the alluvial lowlands of the Santiago and Cayapas River basins. We question here the relation between the two following phenomenons, natural disaster and cultural flowering.

A Synopsis of New Plant Distributional Records from the Foja Mountains of Papua Province, Indonesia

Abstract. Plant distributional records are reported from Conservation International's Foja expeditions. The floristic range extensions are compiled from alluvial lowland forest and cloudy upland habitats to 1900 m. Sixteen taxa are briefly discussed, including 4 ferns, 1 monocot, and 11 dicots. Synonymies are newly proposed for Embelia kuborensis (Myrsinaceae), Medinilla sapoi-riverensis (Melastomataceae), and Pneumatopteris subappendiculata (Thelypteridaceae).

The origin of rice cultivation in the Lower Yangtze Region, China

About the former half of the sixth millennium bc (Kuahuqiao culture) settlement area expanded to alluvial lowlands in the lower Yangtze region, and during the fifth millennium bc (Hemudu culture), adaptation to the wetland settings established. Although older rice remains have been found in this area, it is safe to say that rice cultivation began during Kuahuqiao and Hemudu cultures. At the beginning, it was only a part of broad-spectrum production highly dependent on lacustrine resources, and it took another millennium to establish the ancient civilization (Liangzhu culture) based on rice cultivation.

バングラデシュ中央部，ジャムナ川中流域における 地形環境変遷と屋敷地の形成過程

バングラデシュ中央部，ジャムナ川中流域における 地形環境変遷と屋敷地の形成過程

Ancient Mesopotamia at the dawn of civilization: the evolution of an urban landscape

The alluvial lowlands of the Tigris and Euphrates rivers in southern Mesopotamia are widely known as the 'cradle of civilization' owing to the scale of the processes of urbanization that had taken place in the area by the second half of the fourth millennium BC.In Ancient Mesopotamia at the Dawn of Civilization, Guillermo Algaze draws on the work of modern economic geographers to explore how the unique river-based ecology and geography of the Tigris-Euphrates alluvium impacted the development of urban civilization in southern Mesopotamia. He argues that these natural conditions granted southern polities significant competitive advantages over their landlocked rivals elsewhere in Southwest Asia, most importantly the ability to easily transport commodities.In due course, this resulted in increased trade and economic activity and higher population densities in the south than were possible elsewhere. As southern polities grew in scale and complexity throughout the fourth millennium, revolutionary new forms of labor organization and record keeping were created, and it is these socially created innovations, Algaze argues, that ultimately account for why fully developed city-states emerged earlier in southern Mesopotamia than elsewhere in Southwest Asia or the world.

Avulsões no Pantanal: dimensões naturais e sociais no rio Taquari

O rio Taquari tem um importante significado na história do estado de Mato Grosso do Sul. Nas últimas décadas as recentes alterações causadas por avulsão no leito rio Taquari, na bacia sedimentar quaternária do Pantanal na região Centro-Oeste do Brasil têm causado grandes conseqüências socioambientais. O Pantanal é formado por vários leques aluviais e o maior deles é leque do rio Taquari que tem dois compartimentos geomorfológicos: um cinturão de meandros e o lobo distributário. Nesses compartimentos nos últimos anos foram registrados acelerados processos, sendo no primeiro a migração das margens e no segundo o rompimento dos diques marginais por avulsão, provocando a mudança de direção do rio. A população residente convive com a situação de conflito, e ante esses fenômenos são registradas ações humanas para impedir novas aberturas de canais no rio. A dinâmica no leque aluvial é um processo natural e no futuro podem ocorrer novas mudanças no canal do rio Taquari.

Analysis of Rigid Short Caisson with Granular Core Incorporating Nonlinear Interface and Base Responses

It is difficult to construct a conventional shallow foundation in alluvial lowlands because of soft soils and high ground water table. A rigid short caisson foundation with granular core is being proposed for alluvial lowlands. The proposed foundation is analyzed using non-linear hyperbolic stress–displacement responses of homogeneous alluvial deposits. Extensive parametric studies are carried out to study the effects of length ratio (L/d0), diameter ratio (d/d0) of granular core with respect to casing, relative stiffness of shaft (ατ), relative casing base stiffness (αb), and friction angle of granular material (ϕgp) on the load sharing and the settlement of the proposed foundation.

新潟・長野両県境の関田山脈と飯山盆地の形成に関する造地形運動の研究

We studied the morphogenetic movements associated with the formation of the Sekita Mountains and Iiyama Basin situated at the boundary between the Niigata and Nagano prefectures in central Japan. As a result, we obtained following conclusions. (1) The morphogenetic movement of the Sekita Mountains is a semicylindrical upwarping originating from faulting at both sides of the mountains. The origin was an inclined thrust of a basal block. In addition, it is assumed that the upheaval of the mountains due to a change in isostasy caused by erosion resulted in the four-thousand meter thick strata that constitutes the mountains, and erosion originated from a fold in the strata occurring in the middle Pleistocene. (2) The morphogenetic movement constituting the Iiyama Basin is a reverse fault, which originated from tilting and drawing of the basal crust as a result of a semicylindrical upwarping of the Kato Mountains situated at the east side of the Iiyama Basin. The upwarping was caused by magma ascending from a deep part of the crust. Therefore, the Iiyama Basin was formed as a fault-angle basin. The mountain body of Kenasi Volcano tilted toward the west through the process of forming the Iiyama Basin. We think the Iiyama Basin continued to subside at the rate of about one millimeter a year in the Holocene, based on radiocarbon dating of drilling core samples collected from sediments in the alluvial lowlands.

Mining and environmental change in Sierra Leone, West Africa: a remote sensing and hydrogeomorphological study

This paper evaluates the environmental changes in southwestern Sierra Leone, West Africa from rutile (titanium dioxide) between 1967 and 1995. Mining in peripheral parts of the world economy is a consequence of larger global economic interests. Historically, long-distance trade and export production of minerals and other natural resources primarily for the benefit of core countries are responsible for transforming the natural environment and landscapes of peripheral sectors of the world economy. Tracking environmental change in developing countries such as Sierra Leone is challenging because of financial and infrastructural constraints on the use of ground methods of evaluation and monitoring. Remote sensing data are invaluable in assessing the human dimensions of Land Use and Land Cover Change (LULCC) with implications for political ecology. Using available multi-date infrared Landsat images supplemented with field hydrological and biophysical data, we monitored the rapid temporal and spatial dynamic characteristic of mining areas in the study area with a focus on physical changes to the landscape. Reservoir construction for mining has caused flooding of alluvial lowlands, deforestation, and the creation of tailings and stockpiles over mined-out portions of the lease. Although the study was conducted at a local scale, it represents the broad, regional, past-to-present manner by which global economic interests exploit natural resources and impact the environment in distant places.

Succession and community gradients of arctic macrolichens and their relation to substrate, topography, and rockiness

We describe lichen community structure and its relation to environment in the Bering Land Bridge National Preserve in northwestern Alaska. We used a stratified random sample to estimate macrolichen abundance and several environmental variables from 78 0.38-ha plots within lichen-dominated areas of the Preserve. We found a total of 140 macrolichen taxa. Two primary gradients in lichen species composition were related to habitat rockiness and a substrate-topographic gradient. The strongest gradient, rockiness, correlates with lichen succession. Rocky habitats have less competition from vascular plants and may be more resistant to soil disturbance. The substrate-topography gradient is largely driven by the presence of Sphagnum moss contrasting with calcareous parent rock material. To uncover additional underlying patterns in lichen community composition, we deleted rocky and calcareous plots and strictly saxicolous species from the analyses. Although we found similar patterns from the original analysis in this subset, diversity and community composition also varied with differing microtopography. These gradients of lichen community composition can also be divided into three major groups; rocky non-calcareous sites, calcareous areas, and the remaining plots form the alluvial lowland communities. We used two-way cluster analysis which combines independent clustering of sample units and species into a single diagram. This technique linked individual species and species assemblages with these major trends.

近江盆地湖東平野の地下地質層序と堆積環境―日野川〜愛知川下流域におけるボーリング試料の解析から―

The author studied the alluvial lowland in the lower reaches of the Hino and the Echi Rivers, to clarify landform development of the Kotoh plain to the east shore of Lake Biwa, central Japan, during the middle and late Pleistocene.Four major litho-stratigraphic units (A-D) and five tephra layers (Sakate, AT, DNP, hpm2, Ng-1) were detected from standard penetration test samples of Kominami borehole site cores from the lower reaches of the Hino River. Judging from the facies of the borehole samples and a geological cross-section through the Kominami site in the lower reaches of the Hino and the Echi Rivers, coarse sediments were deposited at least 4 or 5 times during the last 300 ka and the distribution of gravel deposits was much larger especially during the period from ca. 80 to 27 ka than at present. The appearance and shrinkage of the area where gravels were deposited seem to be related to interglacial-glacial or the interstadial-stadial cycles.