The indication of morphological degradation of streams and rivers using Simuliidae

Blackfly communities from five German stream types out of two ecoregions (small and mid-sized siliceous gravel-bed mountain streams of the Central mountains, ecoregion 9, and organic type brooks, small and mid-sized sand-bottomed Central lowland streams of ecoregion 14) are compared. Ecoregional, as well as stream type-specific biocoenotic differences are discussed. The presence of Prosimulium sp. was restricted to mountain streams, whereas Simulium lineatum seemed to prefer mid-sized sand-bottomed Central lowland streams, and S. vernum showed a clear preference for Central lowland streams. An Index of Morphological Stress (IMS), derived from 22 geo-hydromorphological parameters recorded during sampling in the field, is presented. According to the IMS values, sites are divided into morphologically ‘unstressed’ sites (high or good morphological quality) and ‘stressed’ sites (moderate, poor or bad morphological quality), and biocoenotic differences of the two categories are discussed. Two stream types and the entire data set showed significantly higher numbers of taxa at ‘unstressed’ sites. Linear Multiple Regression (LMR) was used to identify geo-hydromorphological parameters that significantly explain the variance of the three most constant taxa, Prosimulium sp., P. hirtipes and Simulium sp. in the LMR model.     

对喜马拉雅地区地壳热状态的初步估计

本文考虑放射性热源,采用非线性稳态有限单元法估算了喜马拉雅地区地壳的温度分布和地表热流值。 喜马拉雅山南、北有不同的地壳温度结构,南部等温线比较均匀,地表热流值低于1.5HFU;北部地表下20公里以上等温线成密集型分布,20公里以下成环状分布,地表热流值从1.5HFU至2.1HFU。根据等温线圈出西藏南部地区地壳内可能存在局部熔融的部位,并与其他地球物理资料作了比较。     

The hydrological significance of mountains: a regional case study,the Ebro River basin,northeast Iberian Peninsula

Abstract

This study evaluated the hydrological significance of mountain regions, comparing them with the lowlands of the Ebro River basin (northeast Iberian Peninsula). It was based on records obtained from measuring stations. An altitude of 1000 m above mean sea level was adopted as the criterion for distinguishing between lowland and mountain areas. We analysed 12 sub-basins whose rivers flow directly into the River Ebro, and which covered 66% of the total surface area, 91% of the mountain area and accounted for 77% of total annual runoff. For the River Ebro basin, we found that the mean precipitation depth, the runoff volume per unit of surface area, and the runoff coefficient were all greater in the mountains than in the adjacent lowlands, with respective differences of 70%, 180% and 60%. These results and the particular fragility of the Mediterranean mountain ecosystems confirm the mountain regions of the Ebro basin as strategic zones for hydrological and territorial planning.

Citation López, R. & Justribó, C. (2010) The hydrological significance of mountains: a regional case study, the Ebro River basin, northeast Iberian Peninsula. Hydrol. Sci. J. 55(2), 223–233.     

Topological invariants of field lines rooted to planes

Abstract

Two open curves with fixed endpoints on a boundary surface can be topologically linked. However, the Gauss linkage integral applies only to closed curves and cannot measure their linkage. Here we employ the concept of relative helicity in order to define a linkage for open curves. For a magnetic field consisting of closed field lines, the magnetic helicity integral can be expressed as the sum of Gauss linkage integrals over pairs of lines. Relative helicity extends the helicity integral to volumes where field lines may cross the boundary surface. By analogy, linkages can be defined for open lines by requiring that their sum equal the relative helicity.

With this definition, the linkage of two lines which extend between two parallel planes simply equals the number of turns the lines take about each other. We obtain this result by first defining a gauge-invariant, one-dimensional helicity density, i.e. the relative helicity of an infinitesimally thin plane slab. This quantity has a physical interpretation in terms of the rate at which field lines lines wind about each other in the direction normal to the plane. A different method is employed for lines with both endpoints on one plane; this method expresses linkages in terms of a certain Gauss linkage integral plus a correction term. In general, the linkage number of two curves can be put in the form L=r + n, |r|≦1J2, where r depends only on the positions of the endpoints, and n is an integer which reflects the order of braiding of the curves.

Given fixed endpoints, the linkage numbers of a magnetic field are ideal magneto-hydrodynamic invariants. These numbers may be useful in the analysis of magnetic structures not bounded by magnetic surfaces, for example solar coronal fields rooted in the photosphere. Unfortunately, the set of linkage numbers for a field does not uniquely determine the field line topology. We briefly discuss the problem of providing a complete and economical classification of field topologies, using concepts from the theory of braid equivalence classes.     

Drainage Density and Relative Relief in Humid Steep Mountains with Frequent Slope Failure

Previous studies in Japanese mountains have shown that drainage density (D) correlates negatively with relief (R) and the erosion rate (E), whereas elsewhere both R and E correlate positively with D. To investigate the inconsistency, this paper compares two types of D–R relations for eight mountain river basins in central Japan. R is computed from a digital elevation model for 1109 morphometric samples of area 0·5 km × 0·5 km. Drainage networks in these cells were first constructed by map criteria applied previously in Japan — deeply notched V-shaped contours with an angle <53°. The resulting D correlates negatively with R, confirming preceding studies. When drainage lines along shallower hollows were added, however, the calculated D essentially constant. These relations arise from active landsliding in high-relief terrains, which has eroded steep channel banks into gentle ones. The decline of channel banks with increasing R is accelerated in terrains underlain by soft rocks, because of rapid erosion. The constant D for all the drainage lines indicates a uniform frequency or spacing of ridges and hollows on hillslopes in rugged humid mountains. Because the D–R and D–E relations for Japan reflect a uniquely Japanese physiographic setting characterized by frequent landsliding, they differ from those relations for other regions where channelization by gullying predominates. © 1997 by John Wiley & Sons, Ltd.     

Impact of a rock avalanche on a moraine‐dammed proglacial lake: Laguna Safuna Alta,Cordillera Blanca,Peru

Moraines that dam proglacial lakes pose an increasing hazard to communities in the Andes and other mountain ranges. The moraines are prone to failure through collapse, overtopping by lake waters or the effect of displacement waves resulting from ice and rock avalanches. Resulting floods have led to the loss of thousands of lives in the Cordillera Blanca mountains of Peru alone in the last 100 years. On 22 April 2002 a rock avalanche occurred immediately to the south‐west of Laguna Safuna Alta, in the Cordillera Blanca. The geomorphic evidence for the nature, magnitude and consequences of this event was investigated in August 2002. Field mapping indicated that the avalanche deposited 8–20 × 10⁶ m³ of rock into the lake and onto the surface of the frontal region of Glaciar Pucajirca, which flows into the lake. Repeated bathymetric surveying indicated that ～5 × 10⁶ m³ of this material was deposited directly into the lake. The immediate effect of this event was to create a displacement wave that gained in height as it travelled along the lake basin, overtopping the impounding moraine at the lake's northern end. To achieve overtopping, the maximum wave height must have been greater than 100 m. This, and subsequent seiche waves, caused extensive erosion of both the proximal and distal faces of the impounding terminal moraine. Further deep gullying of the distal face of this moraine resulted from the supply of pressurized water to the face via a relief overflow tunnel constructed in 1978. Two‐dimensional, steady‐state analysis of the stability of the post‐avalanche moraine rampart indicates that its proximal face remains susceptible to major large‐scale rotational failure. Copyright © 2005 John Wiley & Sons, Ltd.     

Evaluating young fluvial terrace riser degradation using a nonlinear transport model: Application to the Kongur Normal Fault in the Pamir,northwest China

Selecting an appropriate hillslope transport model and calibrating model parameters are essential for morphological dating of fault and fluvial scarps. In this paper, we refine the method of profile-based morphologic dating by updating the representation of nonlinearity in sediment flux dependence on the hillslope gradient. We apply this revised method to fluvial scarps bounding fluvial terraces offset along the Kongur Normal Fault in the semi-arid high-altitude Pamir mountains, northwestern China. One of these terraces, the T3 surface, is dated to 7.0^+1.9/_−1.6 kyr using ¹⁰Be cosmogenic depth profile analysis. Well-preserved, dated terraces make this an ideal site to test the utility of morphological modelling in constraining ages of the young terrace risers. To do this, 35 topographic swath profiles across the terrace risers are extracted from a 0.2 m-resolution digital elevation model produced using structure from motion from photos collected by an unmanned aerial vehicle. The best estimates of morphological age are 13.9 ± 1.3 m² for the riser T3/T4 and 11.9 ± 1.3 m² for T2/T3 using a linear diffusion approach. These two morphological ages overlap within uncertainty and fail to distinguish between two young terrace risers. Alternatively, we employed a nonlinear diffusion model, calibrated with transport constant k = 1 m² kyr⁻¹, nonlinearity n = 2, and critical gradient S_c = tan(33°). This nonlinear model produces ages of 7.3 ± 0.5 kyr for T3/T4 and 4.0 ± 0.2 kyr for T2/T3; these ages are consistent with terrace surface ages deduced by using vertical offset divided by independently determining average throw rate. This comparison shows the advantage of a nonlinear model in defining ages of young scarps. Furthermore, we explored the minor effect of heterogeneous degradation along steep sections of the scarp profiles. The nonlinear scarp modelling scheme we develop in this paper is suitable for studying scarp degradation in other regions. © 2020 John Wiley & Sons, Ltd.     

团树断层场地地震反应的数值模拟

团树断层场地在多次地震中出现了烈度异常。为了弄清烈度异常的原因，应用显式有限元方法，数值模拟了在脉冲地震波斜入射情形下断层场地的地震反应。结果表明：在基岩山脚附近土层场地地震动放大比基岩山区平均高4倍、比远离基岩山脚土层场地平均高2倍，与历史震害分布有较好的对应。     

A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions

During volcanic eruptions, volcanic ash transport and dispersion models (VATDs) are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind. Those models use input parameters, called “eruption source parameters”, such as plume height H, mass eruption rate Ṁ, duration D, and the mass fraction m₆₃ of erupted debris finer than about 4 or 63 μm, which can remain in the cloud for many hours or days. Observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected. Moreover, observed plume height may change during an eruption, requiring rapid assignment of new parameters. This paper reports on a group effort to improve the accuracy of source parameters used by VATDs in the early hours of an eruption. We do so by first compiling a list of eruptions for which these parameters are well constrained, and then using these data to review and update previously studied parameter relationships. We find that the existing scatter in plots of H versus Ṁ yields an uncertainty within the 50% confidence interval of plus or minus a factor of four in eruption rate for a given plume height. This scatter is not clearly attributable to biases in measurement techniques or to well-recognized processes such as elutriation from pyroclastic flows. Sparse data on total grain-size distribution suggest that the mass fraction of fine debris m₆₃ could vary by nearly two orders of magnitude between small basaltic eruptions ( 0.01) and large silicic ones (> 0.5). We classify eleven eruption types; four types each for different sizes of silicic and mafic eruptions; submarine eruptions; “brief” or Vulcanian eruptions; and eruptions that generate co-ignimbrite or co-pyroclastic flow plumes. For each eruption type we assign source parameters. We then assign a characteristic eruption type to each of the world's  1500 Holocene volcanoes. These eruption types and associated parameters can be used for ash-cloud modeling in the event of an eruption, when no observational constraints on these parameters are available.     

Asymmetry of river channel cross-sections: Part I. Quantitative indices

Most river cross-sections display some degree of asymmetry for which there is no adequate quantitative definition. Indices of asymmetry are derived using two principles based on areal differences and maximum depth displacement relative to the channel centreline. The indices are assessed firstly by comparing values for a set of constructed channel shapes which are ranked in order of increasing visual asymmetry, and secondly by analysing a series of 50 cross-sections from a small mountain stream. Two indices, A* and A₂, are probably the most valuable, and could be used to test and generate hypotheses regarding the related changes to cross-sectional and planimetric form which occur during the transition from a straight to a meandering channel, particularly if parallel measures of flow asymmetry are defined. Part II of this paper, concerned with ‘Mode of Development and Local Variation’ will be published in a subsequent issue of this journal.     

Rayleigh波入射下相邻山体地震响应边界元法模拟

采用间接边界元法（IBEM）,对Rayleigh波入射下两邻近山体的地震响应进行了定量分析。结果表明:与单个山体在Rayleigh波入射下的地震响应相比,两山地形的地震反应规律更为复杂,反应特征受控于入射波频率和山体间距等因素。总体上看:入射Rayleigh波频率较低时,两山间距对双山地形地震反应影响较大。低频波入射,受邻近山体影响,迎波面山体水平位移峰值约为入射波水平位移的6.3倍,放大效应可达单山作用的1.5倍。且山体山脚处竖向位移的频谱振荡更为剧烈,特定频率下山脚的竖向位移反应可达单山放大效应的1.6倍。较高频波入射时,迎波面一侧山体受邻近山体影响较小,且对波表现出明显的屏障效应,背波面山体地震反应强度被削弱。     

Deciphering controls for debris-flow erosion derived from a LiDAR-recorded extreme event and a calibrated numerical model (Roßbichelbach,Germany)

Debris flows are among the most destructive and hazardous mass movements on steep mountains. An understanding of debris-flow erosion, entrainment and resulting volumes is a key requirement for modelling debris-flow propagation and impact, as well as analysing the associated risks. As quantitative controls of erosion and entrainment are not well understood, total volume, runout and impact energies of debris flows are often significantly underestimated. Here, we present an analysis of geomorphic change induced by an erosive debris-flow event in the German Alps in June 2015. More than 50 terrestrial laser scans of a 1.2 km long mountain torrent recorded geomorphic change in comparison to an airborne laser scan performed in 2007. Errors were calculated using a spatial variable threshold based on the point density of airborne laser scanning and terrestrial laser scanning and the slope of the digital elevation models. Highest erosion rates approach 5.0 m³/m² (mean 0.6 m³/m²). During the event 9550 ± 1550 m³ was eroded whereas only 650 ± 150 m³ was deposited in the channel. Velocity, flow pressure, momentum and shear stress were calculated using a carefully calibrated RAMMS Debris Flow model including material entrainment. Here we present a linear regression model relating debris-flow erosion rates to momentum and shear stress with an R² up to 68%. Channel transitions from bedrock to loose debris sections cause excessive erosion up to 1 m³/m² due to previously unreleased random kinetic energy now available for erosion. © 2019 John Wiley & Sons, Ltd.     

Identifying surface water evaporation loss of inland river basin based on evaporation enrichment model

Accurately quantifying the evaporation loss of surface water is essential for regional water resources management, especially in arid and semi-arid areas where water resources are already scarce. The long-term monitoring of stable isotopes (δ¹⁸O and δ²H) in water can provide a sensitive indicator of water loss by evaporation. In this study, we obtained surface water samples of Shiyang River Basin from April to October between 2017 and 2019. The spatial and temporal characteristics of stable isotopes in surface water show the trend of enrichment in summer, depletion in spring, enrichment in deserts and depletion in mountains. The Local Evaporation Line (LEL) obtained by the regression of δ²H and δ¹⁸O in surface water has been defined by the lines: δ²H = 7.61δ¹⁸O + 14.58 for mountainous area, δ²H = 4.19δ¹⁸O − 17.85 for oasis area, δ²H = 4.08δ¹⁸O − 18.92 for desert area. The slope of LEL shows a gradual decrease from mountain to desert, indicating that the evaporation of surface water is gradually increasing. The evaporation loss of stable isotopes in surface water is 24.82% for mountainous area, 32.19% for oasis area, and 70.98% for desert area, respectively. Temperature and air humidity are the main meteorological factors affecting the evaporation loss, and the construction of reservoirs and farmland irrigation are the main man-made factors affecting the evaporation loss.     

不同时期菰(Zizania latifolia)幼苗对短期淹没的形态学响应

菰(Zizania latifolia)是长江中下游流域常见的挺水植物.为了解菰在野外的扩张和退化机制,本研究通过模拟实验分析了不同时期菰幼苗对短期淹没的形态学响应.实验共选择株高36和70 cm两种幼苗,设计不淹没、50%淹没和100%淹没3个处理.研究结果表明:两组菰幼苗地上部分的形态学响应有一定差异.在100%淹没处理下,36 cm幼苗组株高最低,茎粗和最大叶宽均显著低于其他两个处理;而70 cm幼苗组在不淹没处理下株高最低,茎粗和最大叶宽在50%和100%淹没处理下均无显著差异.两组菰幼苗根系的形态学响应也不一致.36 cm幼苗组,100%淹没处理组的所有6个根系指标均与其他两种处理有显著差异;70 cm幼苗组,不淹没处理组的6个根系指标均与其他两种处理有显著差异.随着淹没深度的增加,两组菰幼苗总生物量和根茎比均逐渐下降;但36 cm幼苗组在100%淹没处理下总生物量和根茎比均显著低于其他两个处理,而70 cm幼苗组在50%和100%淹没处理下却无显著差异.综合以上分析,本研究结果表明随着菰幼苗的生长,其对淹没的形态学响应能力增强.本研究结果对长江中下游湖泊菰的生态调控具有重要意义.     

Optimized Seismic Threshold Monitoring – Part 1: Regional Processing

v--v Continuous seismic threshold monitoring is a technique that has been developed over the past several years to assess the upper magnitude limit of possible seismic events that might have occurred in a geographical target area. The method provides continuous time monitoring at a given confidence level, and can be applied in a site-specific, regional or global context.¶In this paper (Part 1) and a companion paper (Part 2) we address the problem of optimizing the site-specific approach in order to achieve the highest possible automatic monitoring capability of particularly interesting areas. The present paper addresses the application of the method to cases where a regional monitoring network is available. We have in particular analyzed events from the region around the Novaya Zemlya nuclear test site to develop a set of optimized processing parameters for the arrays SPITS, ARCES, FINES, and NORES. From analysis of the calibration events we have derived values for beam-forming steering delays, filter bands, short-term average (STA) lengths, phase travel times (P and S waves), and amplitude-magnitude relationships for each array. By using these parameters for threshold monitoring of the Novaya Zemlya testing area, we obtain a monitoring capability varying between m_b 2.0 and 2.5 during normal noise conditions.¶The advantage of using a network, rather than a single station or array, for monitoring purposes becomes particularly evident during intervals with high global seismic activity (aftershock sequences), high seismic noise levels (wind, water waves, ice cracks) or station outages. For the time period November-December 1997, all time intervals with network magnitude thresholds exceeding m_b 2.5 were visually analyzed, and we found that all of these threshold peaks could be explained by teleseismic, regional, or local signals from events outside the Novaya Zemlya testing area. We could therefore conclude within the confidence level provided by the method, that no seismic event of magnitude exceeding 2.5 occurred at the Novaya Zemlya test site during this two-month time interval.¶As an example of particular interest in a monitoring context, we apply optimized threshold processing of the SPITS array for a time interval around 16 August 1997 m_b 3.5 event in the Kara Sea. We show that this processing enables us to detect a second, smaller event from the same site (m_b 2.6), occurring about 4 hours later. This second event was not defined automatically by standard processing.     

Global distribution of volcanic centers and mountains on Io: Control by asthenospheric heating and implications for mountain formation

Jupiter's moon Io possesses numerous tectonic mountains in addition to its ubiquitous volcanoes and volcanic features. Remarkably, a distinct global anticorrelation exists between the spatial distribution of mountains and volcanic centers on Io. This relationship indicates an explicit connection between volcanism and mountain formation, even though the mountains are tectonic in origin (predominantly upthrusted crustal blocks). Spherical harmonic analysis shows the distribution of mountains and volcanic centers have statistically significant power at degree 2; this result is especially striking for the volcanic center distribution, and directly implicates models of asthenospheric tidal heating. The latter predict enhanced heat flux along the equator in a degree-two pattern that matches observations. Mountain formation on Io appears to be a form of dominantly vertical tectonism unique in the modern Solar System: continual burial by widespread volcanism drives the crust inward, which leads to strong compression, and at discrete locations, mountains. Correlation coefficients between the volcanic and mountain distributions indicate statistically meaningful anticorrelation at low spectral degrees (l = 1, 2, 4, and 6); the anticorrelation is especially significant between the longitudinal (sectorial) l = 2 components when considered on their own. We compare this anticorrelation with published models that link volcano and mountain formation. While consistent in part with l = 2 convection models, which predict such an anticorrelation (in principle), such low degree anticorrelations are also (if not more) compatible with mountain formation due to, or influenced by, thermal expansion of Io's crust, and deep compression and thrust faulting in regions of lower than average volcanic heat-piping. Positive correlations between mountain and volcanic center distributions at high spectral degree may reflect structural links between a good fraction of mountain blocks and adjacent volcanic paterae, whereas the anticorrelation at low degree implies that most volcanic features (which are far more numerous overall) form independently of mountains.     

The use of instantaneous velocity in uplift investigations

Uplift and the accompanying reduction in overburden result in anomalously high velocity in the uplifted rock unit relative to its current depth. The present work utilizes the non‐uniqueness of the parameters of instantaneous velocity versus depth functions as an effective tool for uplift studies. The linear function with its two parameters, V₀ and k, is a very simple function and is used as the illustrative vehicle. In the parameter space, i.e. in a plot where one axis represents V₀ and the other axis represents k, non‐uniqueness can be represented by contours of equal goodness‐of‐fit values between the observed data and the fitted function. The contour delimiting a region of equivalent solutions in the parameter space is called a ‘solution trough’. Uplift corresponds to a rotation of the solution trough in the parameter space. It is shown that, in terms of relative depth changes, there are five possible configurations (five cases) of uplift in a given area (the mobile location) relative to another area (the reference location). The cases depend on whether the uplifted location had attained a (pre‐uplift) maximum depth of burial that was greater than, similar to, or smaller than the maximum depth of burial at the reference location. Interpretation of the relationships between the solution troughs corresponding to the different locations makes it possible to establish which of the five cases applies to the uplifted location and to estimate the amount of uplift that the unit had undergone at that location. The difficulty in determining the reduction in velocity due to decompaction resulting from uplift is a main source of uncertainty in the estimate of the amount of uplift. This is a common problem with all velocity‐based methods of uplift estimation. To help around this difficulty, the present work proposes a first‐order approximation method for estimating the effect of decompaction on velocity in an uplifted area.     

基于随机振动模型的强地面运动数值模拟及其在广西灵山M6(3/4)地震中的应用

1936年4月1日广西灵山县平山镇东南罗阳山附近发生M6(3/4)地震,该地震是华南大陆自有地震记载以来发生的最大地震。本研究收集整理了灵山M6(3/4)地震的地质资料、活动断层探测最新成果等,选取适当的研究区域,利用随机振动有限断层模型计算区域内网格点的峰值加速度(PGA)及峰值速度(PGV)等参数,并且加入浅层横波速度结构V_s³⁰对地震动参数的影响,最终得到此次地震的地震动分布并分析了地震动特征。本研究将模拟结果与野外调查烈度数据和地震动衰减关系进行对比,结果显示模拟结果与调查烈度值和衰减关系在整体衰减特征、极震区的分布等方面均符合较好,模拟结果可为该地区未来地震危害性评估提供依据。本研究所使用的方法流程亦可应用于本地区地震烈度速报,为震后应急救援及决策指挥提供帮助。     

地-空瞬变电磁法电阻率成像研究与应用

地-空瞬变电磁法(Semi-airborne transient electromagnetic,SATEM)凭借适应能力强、探测深度大、实时性强等特点,适用于湖泊、沼泽、山区等地形复杂地区观测.SATEM接收数据量大、精度要求高,传统成像方法基于地面视电阻率计算未考虑飞行高度,开展SATEM的高精度快速成像研究对实际...     

Identification of calanco,a badland landform in the northern Apennines,Italy

Calanco (plural, calanchi) is a term widely used in the northern Apennines, Italy, to define a type of badland formed in clayey bedrock. However, no precise geomorphological definition of calanco has been established and a variety of map symbols are used to indicate the presence of calanco landforms. With the aim of developing an improved approach to identifying calanchi, a group of experienced surveyors identified 24 catchments with calanco characteristics among 67 catchments located between Bologna and Faenza in the northern Apennines. The morphology of each catchment was classified using traditional quantitative geomorphic approaches including fieldwork, map interpretation, hypsometric curve construction and computation of the annual sediment yield. Consideration of the parameters produced by these approaches indicated that none was capable of representing the presence of calanchi unequivocally and the basins were grouped into five classes on the basis of number and type of calanco criteria that they met. A characteristic of calanchi that is evident on topographic maps is crenulation of the contour lines and in this study a new topographic parameter was developed to represent the degree of contour crenulation. This parameter, LO/LF, is defined as the ratio of the actual length of a contour line (LO) to the length of the same line smoothed by an algorithm based on a moving average (LF). Calculated values of LO/LF ranged from 1·05 to 1·38. To test whether high values of the contour crenulation parameter were associated with calanchi, LO/LF values were added to other criteria for the five classes of catchment. Class 1 catchments, consisting of 14 of the 24 calanchi catchments identified in the field, displayed all of the criteria defining calanchi, and were characterized by the highest values of LO/LF (mean value 1·27 ± 0·15). It is proposed, therefore, that the contour crenulation ratio (LO/LF) may be useful in identifying the calanco landform. Copyright © 2000 John Wiley & Sons, Ltd.