The potential for catastrophic dam failure at Lake Nyos maar,Cameroon

The upper 40 m of Lake Nyos is bounded on the north by a narrow dam of poorly consolidated pyroclastic rocks, emplaced during the eruptive formation of the Lake Nyos maar a few hundred years ago. This 50-m-wide natural dam is structurally weak and is being eroded at an uncertain, but geologically alarming, rate. The eventual failure of the dam could cause a major flood (estimated peak discharge, 17000 m³/s) that would have a tragic impact on downstream areas as far as Nigeria, 108 km away. This serious hazard could be eliminated by lowering the lake level, either by controlled removal of the dam or by construction of a 680-m-long drainage tunnel about 65 m below the present lake surface. Either strategy would also lessen the lethal effects of future massive CO₂ gas releases, such as the one that occurred in August 1986.     

U-series dating of Lake Nyos maar basalts,Cameroon (West Africa): Implications for potential hazards on the Lake Nyos dam

From previously published ¹⁴C and K–Ar data, the age of formation of Lake Nyos maar in Cameroon is still in dispute. Lake Nyos exploded in 1986, releasing CO₂ that killed 1750 people and over 3000 cattle. Here we report results of the first measurements of major elements, trace elements and U-series disequilibria in ten basanites/trachy-basalts and two olivine tholeiites from Lake Nyos. It is the first time tholeiites are described in Lake Nyos. But for the tholeiites which are in ²³⁸U–²³⁰Th equilibrium, all the other samples possess ²³⁸U–²³⁰Th disequilibrium with 15 to 28% enrichment of ²³⁰Th over ²³⁸U. The (²²⁶Ra/²³⁰Th) activity ratios of these samples indicate small (2 to 4%) but significant ²²⁶Ra excesses. U–Th systematics and evidence from oxygen isotopes of the basalts and Lake Nyos granitic quartz separates show that the U-series disequilibria in these samples are source-based and not due to crustal contamination or post-eruptive alteration. Enrichment of ²³⁰Th is strong prima facie evidence that Lake Nyos is younger than 350 ka. The ²³⁰Th–²²⁶Ra age of Nyos samples calculated with the (²²⁶Ra/²³⁰Th) ratio for zero-age Mt. Cameroon samples is 3.7 ± 0.5 ka, although this is a lower limit as the actual age is estimated to be older than 5 ka, based on the measured mean ²³⁰Th/²³⁸U activity ratio. The general stability of the Lake Nyos pyroclastic dam is a cause for concern, but judging from its ²³⁰Th–²²⁶Ra formation age, we do not think that in the absence of a big rock fall or landslide into the lake, a big earthquake or volcanic eruption close to the lake, collapse of the dam from erosion alone is as imminent and alarming as has been suggested.     

A trigger mechanism for the Lake Nyos disaster

The catastrophic release of carbon dioxide gas from Lake Nyos on 21 August 1986 is discussed in the context of the buoyancy reversal instability. Originally proposed by Randall (1980) [Randall, D.S., 1980. Conditional instability of the first kind upside-down. Journal of Atmospheric Sciences 37: 125–130.] and Deardoff (1980) [Deardoff, J.W., 1980. Cloud-top entrainment instability. Journal of Atmospheric Sciences 37: 131–147.] for the `cloud-top entrainment instability' of stratocumulus clouds, the buoyancy reversal instability has been studied experimentally in water tank experiments by Shy and Breidenthal (1990) [Shy, S.S., Breidenthal, R.E., 1990. Laboratory experiments on the cloud-top entrainment instability. Journal of Fluid Mechanics 214: 1–15.], who identified three criteria for instability. The initial disturbance must be sufficiently large, so that its Reynolds number is above the mixing transition, its Richardson number must be less than one to achieve overturning and mixing, and the buoyancy reversal parameter must be greater than a critical value, of order one. The implications and applicability of these criteria to Lake Nyos are discussed. The criterion for the Reynolds number is easily satisfied for typical wind velocities in the Lake Nyos region. Similarly, the Richardson number based on incident turbulence is easily less than unity, and therefore satisfy the second criterion for instability. In the case of Lake Nyos, the continuous release of carbon dioxide at the bottom of the lake increases the value of the buoyancy reversal parameter until it reaches its critical value, at which point an explosion occurs. This instability provides a plausible trigger for the 1986 explosion. After each explosion, the buoyancy reversal parameter returns to below its critical value, only to slowly rise again over time, as CO₂ continues to enter the lake, setting the stage for the next explosion. Future explosions may be avoided if the value of the buoyancy reversal parameter is prevented from approaching its critical value by artificial mixing at the thermocline, such as with a bubble plume.     

How much water swept over the Lake Nyos dam during the 1986 gas disaster?

The toxic aerosol of water and carbon dioxide which was released from Lake Nyos in August 1986 passed over the natural dam which confines the lake and devastated the valleys to the north. The gas release generated a wave of water which swept across the lake surface and damaged vegetation on the eastern and southern shore. However, the vegetation to either side of the spillway was undamaged and therefore, despite a recent suggestion to the contrary, any wave of water which passed over the dam could have been no more than a few centimetres high.     

Recent pH and CO2 profiles at Lakes Nyos and Monoun, Cameroon: implications for the degassing strategy and its numerical simulation

In situ pH profiles are reported for the first time for Lakes Nyos and Monoun. The pH profiles were converted to CO₂ profiles using HCO₃⁻ profiles calculated from conductivity data. Recent observations (1993–1996) at Lake Nyos indicates that CO₂ still accumulates below 180 m depth at a rate of 125 Mmol year⁻¹. At Lake Monoun, the majority of CO₂ is present below a depth of 60 m, only 25 m below the saturation depth. Consequently, a potential danger of gas explosion is high at both lakes, and artificial degassing of the lakes should be performed as soon as possible. A system for industrial degassing of the lakes is proposed. The system, based on the self-sustained gas lift principle, consists of multiple pipes (14 cm in diameter) with different intake depths; 12 pipes for Lake Nyos (four each at 185, 195 and 205 m) and three pipes for Lake Monoun (at 70, 80 and 90 m). The stepped degassing at different depths is intended to keep the maximum stability of the lakes. The proposed degassing operation was simulated using the code for both lakes. In 5 years, approximately 50% of currently dissolved CO₂ in Lake Nyos and 90% in Lake Monoun will be removed. The expected changes in the thermal and chemical structures of the lakes as degassing proceeds will be most easily monitored with a carefully calibrated CTD equipped with a pH sensor. The simulation indicates that the discharged degassed water will sink to a level of neutral buoyancy, i.e. to a maximum of 70 m at Lake Nyos and 35 m at Lake Monoun. There would be no possibility of triggering a gas explosion by this plunge of discharged water because the water present there would have already been replaced by water at lower CO₂ concentration, during the degassing from shallower pipes.     

Development and sensitivity analysis of a model for assessing stratification and safety of Lake Nyos during artificial degassing

To prevent the recurrence of a disastrous eruption of carbon dioxide (CO₂) from Lake Nyos, a degassing plan has been set up for the lake. Since there are concerns that the degassing of the lake may reduce the stability of the density stratification, there is an urgent need for a simulation tool to predict the evolution of the lake stratification in different scenarios. This paper describes the development of a numerical model to predict the CO₂ and dissolved solids concentrations, and the temperature structure as well as the stability of the water column of Lake Nyos. The model is tested with profiles of CO₂ concentrations and temperature taken in the years 1986 to 1996. It reproduces well the general mixing patterns observed in the lake. However, the intensity of the mixing tends to be overestimated in the epilimnion and underestimated in the monimolimnion. The overestimation of the mixing depth in the epilimnion is caused either by the parameterization of the k-epsilon model, or by the uncertainty in the calculation of the surface heat fluxes. The simulated mixing depth is highly sensitive to the surface heat fluxes, and errors in the mixing depth propagate from one year to the following. A precise simulation of the mixolimnion deepening therefore requires high accuracy in the meteorological forcing and the parameterization of the heat fluxes. Neither the meteorological data nor the formulae for the calculation of the heat fluxes are available with the necessary precision. Consequently, it will be indispensable to consider different forcing scenarios in the safety analysis in order to obtain robust boundary conditions for safe degassing. The input of temperature and CO₂ to the lake bottom can be adequately simulated for the years 1986 to 1996 with a constant sublacustrine source of 18 l s^–1 with a CO₂ concentration of 0.395 mol l^–1 and a temperature of 26 °C. The results of this study indicate that the model needs to be calibrated with more detailed field data before using it for its final purpose: the prediction of the stability and the safety of Lake Nyos during the degassing process.Responsible Editor: Hans Burchard     

10,000 Years of explosive eruptions of Merapi Volcano, Central Java: archaeological and modern implications

Stratigraphy and radiocarbon dating of pyroclastic deposits at Merapi Volcano, Central Java, reveals 10,000 years of explosive eruptions. Highlights include:(1) Construction of an Old Merapi stratovolcano to the height of the present cone or slightly higher. Our oldest age for an explosive eruption is 9630±60 ¹⁴C y B.P.; construction of Old Merapi certainly began earlier.(2) Collapse(s) of Old Merapi that left a somma rim high on its eastern slope and sent one or more debris avalanche(s) down its southern and western flanks. Impoundment of Kali Progo to form an early Lake Borobudur at 3400 ¹⁴C y B.P. hints at a possible early collapse of Merapi. The latest somma-forming collapse occurred 1900 ¹⁴C y B.P. The current cone, New Merapi, began to grow soon thereafter.(3) Several large and many small Buddhist and Hindu temples were constructed in Central Java between 732 and 900 A.D. (roughly, 1400–1000 ¹⁴C y B.P.). Explosive Merapi eruptions occurred before, during and after temple construction. Some temples were destroyed and (or) buried soon after their construction, and we suspect that this destruction contributed to an abrupt shift of power and organized society to East Java in 928 A.D. Other temples sites, though, were occupied by “caretakers” for several centuries longer.(4) A partial collapse of New Merapi occurred <1130±50 ¹⁴C y B.P. Eruptions 700–800 ¹⁴C y B.P. (12–14th century A.D.) deposited ash on the floors of (still-occupied?) Candi Sambisari and Candi Kedulan. We speculate but cannot prove that these eruptions were triggered by (the same?) partial collapse of New Merapi, and that the eruptions, in turn, ended “caretaker” occupation at Candi Sambisari and Candi Kedulan. A new or raised Lake Borobudur also existed during part or all of the 12–14th centuries, probably impounded by deposits from Merapi.(5) Relatively benign lava-dome extrusion and dome-collapse pyroclastic flows have dominated activity of the 20th century, but explosive eruptions much larger than any of this century have occurred many times during Merapi's history, most recently during the 19th century.Are the relatively small eruptions of the 20th century a new style of open-vent, less hazardous activity that will persist for the foreseeable future? Or, alternatively, are they merely low-level “background” activity that could be interrupted upon relatively short notice by much larger explosive eruptions? The geologic record suggests the latter, which would place several hundred thousand people at risk. We know of no reliable method to forecast when an explosive eruption will interrupt the present interval of low-level activity. This conclusion has important implications for hazard evaluation.     

Tungurahua Volcano,Ecuador: structure,eruptive history and hazards

Tungurahua, one of Ecuador's most active volcanoes, is made up of three volcanic edifices. Tungurahua I was a 14-km-wide andesitic stratocone which experienced at least one sector collapse followed by the extrusion of a dacite lava series. Tungurahua II, mainly composed of acid andesite lava flows younger than 14,000 years BP, was partly destroyed by the last collapse event, 2955±90 years ago, which left a large amphitheater and produced a ∼8-km³ debris deposit. The avalanche collided with the high ridge immediately to the west of the cone and was diverted to the northwest and southwest for ∼15 km. A large lahar formed during this event, which was followed in turn by dacite extrusion. Southwestward, the damming of the Chambo valley by the avalanche deposit resulted in a ∼10-km-long lake, which was subsequently breached, generating another catastrophic debris flow. The eruptive activity of the present volcano (Tungurahua III) has rebuilt the cone to about 50% of its pre-collapse size by the emission of ∼3 km³ of volcanic products. Two periods of construction are recognized in Tungurahua's III history. From ∼2300 to ∼1400 years BP, high rates of lava extrusion and pyroclastic flows occurred. During this period, the magma composition did not evolve significantly, remaining essentially basic andesite. During the last ∼1300 years, eruptive episodes take place roughly once per century and generally begin with lapilli fall and pyroclastic flow activity of varied composition (andesite+dacite), and end with more basic andesite lava flows or crater plugs. This pattern is observed in the three historic eruptions of 1773, 1886 and 1916–1918. Given good age control and volumetric considerations, Tungurahua III growth's rate is estimated at ∼1.5×10⁶ m³/year over the last 2300 years. Although an infrequent event, a sector collapse and associated lahars constitute a strong hazard of this volcano. Given the ∼3000 m relief and steep slopes of the present cone, a future collapse, even of small volume, could cover an area similar to that affected by the ∼3000-year-old avalanche. The more frequent eruptive episodes of each century, characterized by pyroclastic flows, lavas, lahars, as well as tephra falls, directly threaten 25,000 people and the Agoyan hydroelectric dam located at the foot of the volcano.     

Volcanoes of the Cape Hoskins area,New Britain,territory of Papua and New Guinea

One active and ten extinct Quaternary volcanoes are described from the Cape Hoskins area, on the north coast of New Britain. They are mostly strato volcanoes built up of lava flows, lava domes, pyroclastic flows, lahars, tephra, and derived alluvial sediments. The volcanic products range in composition from basalt to rhyolite, but basaltic andesite and andesite predominate. Much of the area is covered by tephra, several metres thick, consisting mainly of rhyolitic pumice. The active volcano, Pago, is built up of several glacier-like lava flows, the last of which was formed during an eruption in 1914–18. Pago lies within a well-preserved caldera forming the central part of a broad low-angle cone, named Witori, which consists largely of welded and unwelded pyroclastic flow deposits. C-14 dates obtained on charcoal indicate that the caldera eruption occurred about 2500 years B. P. Another caldera of similar age lies south of Witori. Of the other eight volcanoes described four are relatively well-preserved steep-sided cones formed mainly of lava flows, one is a remnant of a low-angle cone with a caldera, and three are deeply eroded cones which have none of their constructional surfaces preserved.     

五大连池老黑山火烧山火山喷发物及形成的物理过程

以当代火山物理的观点和思路对黑龙江省五大连池老黑山火烧山进行了研究。在旧锥锥体上部发现滞后角砾岩，在其下部坡脚发现有涌浪（ｓｕｒｇｅ）堆积物的存在，对形成过程和机制做了一些解释。     

Decoupling of small-volume pyroclastic flows and related hazards at Merapi volcano, Indonesia

The November 1994 eruption at Merapi volcano provided good evidence of decoupling of dome-collapse pyroclastic flows and of large-scale detachment of an ash-cloud surge (ACS) component from the basal block-and-ash flow (BAF). Timing and stratigraphic relationships of the largest 1994 ACS indicate that this escaped from the valleys, travelled well ahead of the BAF, arrived at the termination tens of seconds before it and deposited a discrete ACS deposit beneath the BAF unit. This suggests that the ACS detachment mostly occurred relatively high on the volcano slope, likely at the foot of the proximal cone. Later pyroclastic flow eruptions in January 1997 and July 1998 also showed evidence of ACS detachment, although to a lesser extent, suggesting that ACSs could be a frequent hazard at Merapi volcano. Based on an extensive review of the available literature and on field investigations of historical deposits, we show here that flow decoupling and ACS detachment in the way inferred from the 1994 eruption is a common process at Merapi. The ACS-related destructions outside valleys were frequently reported in the recent past activity of the volcano, i.e. in at least 16 pyroclastic flow eruptions since 1927. Destruction occurred systematically in eruptions where maximum runout of the BAFs was 6.5 km or more, and occurred rarely for BAF runouts of 4.5 km or less. The ACS deposits have been recognized beneath some valley-filling BAF units we attribute to some recent destructive eruptions, i.e. the 1930, 1954, 1961 and 1969 eruptions. Topographic conditions at Merapi volcano favouring ACS detachment include: (a) the high slope (30°) of the proximal cone, leading to high proximal velocities of the pyroclastic flows and thus to the transfer of large amounts of particles into the ash cloud; (b) the strong break in slope at the foot of the proximal cone, where the velocity of the basal BAF is strongly reduced and a major ACS component is thought to form and detach by shearing over the BAF; and (c) the small depth of most valleys in the first kilometres beyond the foot of the cone, which allows minor ACS components to escape from the valleys during travel of the BAF; however, flow decoupling and ACS detachment occur for only some of the numerous pyroclastic flows that follow the same path in a given eruption. This indicates that topography alone cannot lead to flow decoupling. We suggest two factors that control flow decoupling and its extent. The main one is flow volume (and thus flux, as both are correlated in almost instantaneous, dome-collapse events), as suggested by the observed relationship between flow decoupling and the travel distance of the pyroclastic flows. The second factor is the amount of available ash in the flow at its early stage, which influences the mass and thus momentum of the ash cloud. The amount of ash in the pyroclastic flows of Merapi may depend on several factors, among which are (a) the physical and thermal state of the part of the active dome that collapses, and (b) the proportion of older, cold rocks incorporated in the flow, either by undermining of surrounding summit rocks by the current pyroclastic flow activity or by erosion on the upper slopes.     

An eruptive history of Maderas volcano using new 40Ar/39Ar ages and geochemical analyses

Maderas volcano is a small, andesitic stratovolcano located on the island of Ometepe in Lake Nicaragua, Nicaragua, with no record of historic activity. Twenty-one samples were collected in 2010 from lava flows of Maderas. The selected samples were analyzed for whole-rock geochemistry using ICP-AES and/or were dated using the ⁴⁰Ar/³⁹Ar method. The results of these analyses were combined with previously collected data from Maderas as well as field observations to determine the eruptive history of the volcano and create a geologic map. The results of the geochemical analyses indicate that Maderas has higher concentrations of alkalies than most Nicaraguan and Costa Rican volcanoes including its nearest neighbor, Concepción volcano. It is also different from Concepción in that it displays higher incompatible elements. Determined age dates range from 179.2?±?16.4?ka to 70.5?±?6.1?ka. Based on these ages and the geomorphology of the volcano which is characterized by a bisecting graben, it is proposed that Maderas experienced two generations of development: initial build-up of the older cone including pre-graben lava flows, followed by post-graben lava flows. The ages also indicate that Maderas is markedly older than Concepción which is historically active. Volcanic hazards were also assessed. The ⁴⁰Ar/³⁹Ar ages indicate that Maderas has likely been inactive for tens of thousands of years and future volcanic eruptions are not considered an immediate hazard. However, earthquake and lahar hazards exist for the communities around the volcano. The steep slopes of the eroded older cone are the most likely sources of lahar hazards.     

Continental basaltic volcanoes — Processes and problems

Monogenetic basaltic volcanoes are the most common volcanic landforms on the continents. They encompass a range of morphologies from small pyroclastic constructs to larger shields and reflect a wide range of eruptive processes. This paper reviews physical volcanological aspects of continental basaltic eruptions that are driven primarily by magmatic volatiles. Explosive eruption styles include Hawaiian and Strombolian (sensu stricto) and violent Strombolian end members, and a full spectrum of styles that are transitional between these end members. The end-member explosive styles generate characteristic facies within the resulting pyroclastic constructs (proximal) and beyond in tephra fall deposits (medial to distal). Explosive and effusive behavior can be simultaneous from the same conduit system and is a complex function of composition, ascent rate, degassing, and multiphase processes. Lavas are produced by direct effusion from central vents and fissures or from breakouts (boccas, located along cone slopes or at the base of a cone or rampart) that are controlled by varying combinations of cone structure, feeder dike processes, local effusion rate and topography. Clastogenic lavas are also produced by rapid accumulation of hot material from a pyroclastic column, or by more gradual welding and collapse of a pyroclastic edifice shortly after eruptions. Lava flows interact with — and counteract — cone building through the process of rafting. Eruption processes are closely coupled to shallow magma ascent dynamics, which in turn are variably controlled by pre-existing structures and interaction of the rising magmatic mixture with wall rocks. Locations and length scales of shallow intrusive features can be related to deeper length scales within the magma source zone in the mantle. Coupling between tectonic forces, magma mass flux, and heat flow range from weak (low magma flux basaltic fields) to sufficiently strong that some basaltic fields produce polygenetic composite volcanoes with more evolved compositions. Throughout the paper we identify key problems where additional research will help to advance our overall understanding of this important type of volcanism.     

Depositional ramps: asymmetrical distribution structure in the Ata pyroclastic flow deposit,Japan

The asymmetrical distribution of the welded Ata large-scale pyroclastic flow deposit in Southern Kyushu, Japan was identified. This distribution pattern was defined as depositional ramps. Depositional ramps can be identified in valleys wider than 1 km and become smaller-scale with increasing distance from the source. Upslope directions of depositional ramps are generally radially away from the source caldera, suggesting that the structure was formed by the flow of pyroclastic material radially away from the source. The original depositional surface was reconstructed based on field mapping and density measurements of the pyroclastic flow deposit. Depositional ramps having a dip angle of more than 9° were reconstructed on the vent-facing slopes of the topography underlying the valley-filling deposits in the area within 10 km of the caldera rim. Such a dip angle is much larger than previously described dip angles. The size and gradient of the depositional ramps decreases with increasing distance from the source. Depositional ramps are recognized commonly in densely welded pyroclastic flow deposits. A high emplacement temperature is required to form the depositional ramps. This suggests that the pyroclastic flow was transported as a dense, fluidized layer to minimize heat loss.     

伊兹米特地震的强地震动和地震灾害

介绍了１９９９年８月１７日土耳其伊兹米特７．４级地震的强地震动和地震灾害,包括：伊兹米特级地震的强地面运动、地震烈度分布、地震震害以及地震破坏原因浅析。     

Pyroclastic flow generated by crater-wall collapse and outpouring of the lava pool of Arenal Volcano, Costa Rica

The pyroclastic flow that issued from the Arenal summit crater on 28 August 1993 came from the collapse of the crater wall of the cone and the drainage of a lava pool. The 3-km-long pyroclastic flow, 2.2ǂ.8᎒⁶ m³ in volume, was confined to narrow valleys (30-100 m wide). The thickness of the pyroclastic deposit ranged from 1 to 10 m, and its temperature was about 400 °C, although single bombs were up to 1,000 °C. The deposit is clast-supported, has a bimodal grain size distribution, and consists of an intimate mixture of finely pulverized rock ash, lapilli, small blocks, and cauliflower bread-crusted bombs, in which are set meter-size lava fragments and juvenile and non-juvenile angular blocks, and bombs up to 7 m in diameter. Large faceted blocks make up 50% of the total volume of the deposit. The cauliflower bombs have deep and intricate bread-crust texture and post-depositional vesiculation. It is proposed that the juvenile material was produced entirely from a lava pool, whereas faceted non-juvenile blocks come from the crater-wall collapse. The concentration and maximum diameter of cauliflower bread-crusted bombs increases significantly from the base (rockslide + pyroclastic flow) to the top (the pyroclastic flow) of the deposit. An ash cloud deposited accretionary lapilli in the proximal region (outside of the pyroclastic flow deposit), and very fine ash fell in the distal region (between 5 and 30 km). The accretionary lapilli deposit is derived from the fine, elutriated products of the flow as it moved. A turbulent overriding surge blew down the surrounding shrubbery in the flow direction. The pyroclastic flow from August 1993, similar to the flows of June 1975, May 1998, August 2000, and March 2001, slid and rolled rather than being buoyed up by gas. They grooved, scratched, and polished the surfaces over which they swept, similar to a Merapi-type pyroclastic flow. However, the mechanism of the outpouring of a lava pool and the resulting flows composed of high- to moderate-vesiculated, cauliflower bread-crusted bombs and juvenile blocks have not been described before. High-frequency earthquake swarms, followed by an increase in low-frequency volcanic events, preceded the 1975, 1993, and 2000 eruptions 2-4 months before. These pyroclastic flow events, therefore, may be triggered by internal expansion of the unstable cone in the upper part because of a slight change in the pressure of the magma column (gas content and/or effusive rate). This phenomenon has important short-term, volcanic hazard implications for touristic development of some parts on the flanks of the volcano.     

Modelling the long-term geomorphic response to check dam failures in an alpine channel with CAESAR-Lisflood

Globally, between 1950 and 2011 nearly 80,000 debris flow fatalities occurred in densely populated regions in mountainous terrain. Mitigation of these hazards includes the construction of check dams, which limit coarse sediment transport and in the European Alps number in the 100,000s. Check dam functionality depends on periodic, costly maintenance, but maintenance is not always possible and check dams often fail. As such, there is a need to quantify the long-term (10–100 years) geomorphic response of rivers to check dam failures. Here, for the first time, a landscape evolution model (CAESAR-Lisflood) driven by a weather generator is used to replicate check dam failures due to the lack of maintenance, check dam age, and flood occurrence. The model is applied to the Guerbe River, Switzerland, a pre-Alpine catchment containing 73 check dams that undergo simulated failure. Also presented is a novel method to calibrate CAESAR-Lisflood's hydrological component on this ungauged catchment. Using 100-year scenarios of check dam failure, the model indicates that check dam failures can produce 8 m of channel erosion and a 322% increase in sediment yield. The model suggests that after check dam failure, channel erosion is the remobilization of deposits accumulated behind check dams, and, after a single check dam failure channel equilibrium occurs in five years, but after many check dam failures channel equilibrium may not occur until 15 years. Overall, these findings support the continued maintenance of check dams.     

The Tragedy of the Karama Dam Project/Jordan

The Karama Dam, with a capacity of 55 Mio m³, was constructed in 1995 on Wadi Mallaha in the Jordan Valley area in order to store water for irrigational uses. The dam was constructed in spite of experts' warnings that this dam geologically, hydrogeologically, seismically, and from the points of view of salinity of its water, its management and the water resources to fill it is totally irrelevant, and that the dam will fail to fulfill its purposes. Now after 9 years of its construction the dam fails to collect water because there are no sources available to fill it. The water the farmers were deprived of to partially fill the dam to demonstrate its success became in the dam reservoir highly saline (20 000 μS/cm). Reservoir bottom collapses due to dissolution of salts took place and large water amounts were lost to the underground. Not a single drop of water from the dam has been of any use for any purpose until now. Equipment to pump water for irrigational uses has been corroding, and the government is paying the depreciation, capital, and running cost of a fiasco project.     

洞庭湖城陵矶水道水力几何形态的研究

根据１９５１－１９８８年洞庭湖城陵矶站的水文测验资料,运用Ｌ．Ｂ．Ｌｅｏｐｏｌｄ河床力几何形态原理,建立洞庭湖出口－城陵矶水道河相关系式,研究该水道水力几何形态的特点及变化。研究表明,与河流水道相比,洞庭湖出口水道河宽指数ｂ随流量的变化较小,而水深指数ｆ及流速指数ｍ随流量的变化较大,河床横面具有窄深的特点。