bluuebunny/crossref_metadata_2025 huggingface dataset:
A dynamic rating curve approach to indirect discharge measurement
Authors: Dottori F. , Martina M. L. V. , Todini E.
Published: April 2010

Abstract. The operational measurement of discharge in medium and large rivers is mostly based on indirect approaches by converting water stages into discharge on the basis of steady-flow rating curves. Unfortunately, under unsteady flow conditions, this approach does not guarantee accurate estimation of the discharge due, on the one hand, to the underlying steady state assumptions and, on the other hand, to the required extrapolation of the rating curve beyond the range of actual measurements used for its derivation. Historically, several formulas were proposed to correct the steady-state discharge value and to approximate the unsteady-flow stage-discharge relationship on the basis of water level measurements taken at a single cross section, where a steady state rating curve is available. However, most of them are either over-simplified or based on approximations that prevented their generalisation. Moreover all the mentioned formulas have been rarely tested on cases where their use becomes essential, namely under unsteady-flow conditions characterised by wide loop rating curves. In the present work, a new approach, based on simultaneous stage measurements at two adjacent cross sections, is introduced and compared to the approaches described in the literature. The comparison has been carried out on channels with constant or spatially variable geometry under a wide range of flood wave and river bed slope conditions. The results clearly show the improvement in the discharge estimation and the reduction of estimation errors obtainable using the proposed approach.
A comparative analysis of two wind velocity retrieval techniques by using a single Doppler radar
Authors:   Hee-Chang Lim,   Dong-In Lee
Published: April 2010

Abstract. This study compares the theoretical basis of the two wind velocity retrieval methods, Velocity Azimuth Display (VAD) and Velocity Area Display (VARD) by using data obtained by a single Doppler radar. Two pre-assumed shapes of the wind velocity distribution with altitude are considered, uniform and parabolic. The former presents an approximation of the non-sheared or low-sheared wind flow in the upper troposphere, while the latter is a simplified representation of the Atmospheric Boundary Layer (ABL) in lower troposphere or high-sheared wind flow at the edges of the tropospheric jet streams. Both techniques for the wind velocity retrieval considered in this study are reformulated in order to get more precise information on the wind velocity components. An algorithm is proposed to decrease the uncertainty in retrieving by evaluating the coefficients of the polynomial equation and applying a transfer function with respect to the angle formed between the wind flow and the radar beam direction. It is concluded that, provided the formulated transformation functions are used, the application of the VAD and VARD techniques to the single-Doppler data may be an invaluable tool for solving various climate and wind engineering problems.
A consistent set of trans-basin floods in Germany between 1952–2002
Authors: Uhlemann S. , Thieken A. H. , Merz B.
Published: April 2010

Abstract. Floods that affect many sites simultaneously can pose great challenges in the co-ordination of flood disaster management actions, as well as for the insurance and re-insurance industry, since this type of flooding leads to an accumulation of losses and the risk assessment needs to be extended to a concept representing the spatial risk of flooding. The assessment of the accumulated risk, especially over large domains, requires an analysis of the spatial and temporal coherence of flooding. For Germany the extent of spatial dependence of flooding is largely unknown and no systematic analysis has been performed so far. In this paper, we present a methodology that is capable of capturing the simultaneous occurrence of flooding using multiple series of mean daily discharge. For the first time we present a complete and consistent set of trans-basin floods in Germany for the period between 1952 and 2002. Each flood is characterised by a specific value for the timing, the location and the magnitude of discharges within the entire river network. We propose a measure for quantifying the overall event severity considering both the heterogeneous spatial extent as well as the locally varying magnitudes of a trans-basin flood. In total, we identify 80 trans-basin floods in the entire time period. The set is dominated by events that were recorded in the hydrological winter (64%); 36% occurred during the summer months. 32 events affected more than one third of the entire river network. These most severe events are predominantly winter events. Dividing the study period into two sub-periods, we find an increase in the percentage of winter events from 58% in the first to 70.5% in the second sub-period. Accordingly, we find a significant increase in the number of extreme trans-basin floods in the second sub-period. A natural extension of this study is the quantification of the spatial and temporal dependencies in a multivariate framework. This framework needs to be supported by a flood typology based on the analysis of the physical processes relevant in the genesis of trans-basin floods.
Bi-criteria evaluation of MIKE SHE model for a forested watershed on South Carolina coastal plain
Authors: Dai Z. , Li C. , Trettin C. , Sun G. , Amatya D. , Li H.
Published: April 2010

Abstract. Hydrological models are important tools for effective management, conservation and restoration of forested wetlands. The objective of this study was to test a distributed hydrological model, MIKE SHE by using bi-criteria (two measurable variables, streamflow and water table depth) to describe the hydrological processes in a forested watershed that is characteristic of the lower Atlantic Coastal Plain. Simulations were compared against observations of both streamflow and water table depth measured on a first-order watershed (WS80) on the Santee Experimental Forest in South Carolina, USA. Model performance was evaluated using coefficient of determination (R2) and Nash-Sutcliffe's model efficiency (E). The E and root mean squared error (RMSE) were chosen as objective functions for sensitivity analysis of parameters. The model calibration and validation results demonstrated that the streamflow and water table depth were sensitive to most of the model input parameters, especially to surface detention storage, drainage depth, soil hydraulic properties, plant rooting depth, and surface roughness. Furthermore, the bi-criteria used for distributed model calibration and validation was shown to be better than the single-criterion in obtaining optimum model input parameters, especially for those parameters that were only sensitive to some specific conditions. Model calibration using the bi-criteria approach should be advantageous for constructing the uncertainty bounds of model inputs to simulate the hydrology for this type of forested watersheds. R2 varied from 0.60–0.99 for daily and monthly streamflow, and from 0.52–0.91 for daily water table depth. E changed from 0.53–0.96 for calibration and 0.51–0.98 for validation of daily and monthly streamflow, while E varied from 0.50–0.90 for calibration and 0.66–0.80 for validation of daily water table depth. This study showed that MIKE SHE was applicable for predicting the streamflow and water table depth in this coastal plain watershed.
Sustainability of water resources management in the Indus Basin under changing climatic and socio economic conditions
Authors: Archer D. R. , Forsythe N. , Fowler H. J. , Shah S. M.
Published: April 2010

Abstract. Pakistan is highly dependent on water resources originating in the mountain sources of the upper Indus for irrigated agriculture which is the mainstay of its economy. Hence any change in available resources through climate change or socio-economic factors could have a serious impact on food security and the environment. In terms of both ratio of withdrawals to runoff and per-capita water availability, Pakistan's water resources are already highly stressed and will become increasingly so with projected population changes. Potential changes to supply through declining reservoir storage, the impact of waterlogging and salinity or over-abstraction of groundwater, or reallocations for environmental remediation of the Indus Delta or to meet domestic demands, will reduce water availability for irrigation. The impact of climate change on resources in the Upper Indus is considered in terms of three hydrological regimes – a nival regime dependent on melting of winter snow, a glacial regime, and a rainfall regime dependent on concurrent rainfall. On the basis of historic trends in climate, most notably the decline in summer temperatures, there is no strong evidence in favour of marked reductions in water resources from any of the three regimes. Evidence for changes in trans-Himalayan glacier mass balance is mixed. Sustainability of water resources appears more threatened by socio-economic changes than by climatic trends. Nevertheless, analysis and the understanding of the linkage of climate, glaciology and runoff is still far from complete; recent past climate experience may not provide a reliable guide to the future.
A flume experiment on the effect of constriction shape on the formation of forced pools
Authors: Thompson D. M. , McCarrick C. R.
Published: April 2010

Abstract. A series of 18 flume runs were conducted in a 6-m long, 0.5-m wide recirculating flume with a bed gradient of 0.8% to determine the influence of obstruction shape on the formation and characteristics of forced pools. Six different-shaped obstructions were added to the flume with the maximum width of the obstruction held constant at 20 cm, which equaled a 40% constriction of flow. The obstruction shapes used included a square, a rectangle, a right triangle with the hypotenuse-facing upstream, a right triangle with the hypotenuse-facing downstream, a combination of a square and triangle with the hypotenuse-facing upstream, and a rectangle and semi-circle shape. Three flume runs were conducted with each obstruction shape. A profile of the flume bed was taken after each experiment and a grid measurement of bed elevations for the last run were conducted to create topographic maps of the flume bed to compare pool-riffle morphologies. ANOVA results indicate pool depth, pool location, and the distance between the pool center and the riffle crest all vary with the obstruction shape. Obstructions with a more blunt upstream face created deeper pools, more total scour and longer pool-riffle sequence lengths than pools formed by obstructions with a more gradual narrowing of flow. The increased volume of scour associated with obstructions that rapid narrow flow also creates larger volume riffles that cover a greater extent of the channel bed. Some of the difference in pool shape highlight variations in helical flow development and vortex shedding location that result from different approach conditions of the flow.
Climatology of daily rainfall semivariance in The Netherlands
Authors: van de Beek C. Z. , Leijnse H. , Torfs P. J. J. F. , Uijlenhoet R.
Published: April 2010

Abstract. Rain gauges can offer high quality rainfall measurements at their location. Networks of rain gauges can offer better insight into the space-time variability of rainfall, but they tend to be too widely spaced for accurate estimates between points. While remote sensing systems, such as radars and networks of microwave links, can offer good insight in the spatial variability of rainfall they tend to have more problems in identifying the correct rain amounts at the ground. A way to estimate the variability of rainfall between gauge points is to interpolate between them using fitted variograms. If a dense rain gauge network is lacking it is difficult to estimate accurate variograms. In this paper a 30-year dataset of daily rain accumulations gathered at 29 automatic weather stations operated by KNMI and a one-year dataset of 10 gauges in a network with a radius of 5 km around CESAR (Cabauw Experimental Site for Atmospheric Research) are employed to estimate variograms. Fitted variogram parameters are shown to vary according to season, closely following simple cosine functions allowing for applications in catchment hydrology and rainfall field generation. Semivariances at short ranges during winter and spring tend to be underestimated, but summer and autumn are well predicted. This climatological semivariance can be employed to estimate the accuracy of the rainfall input to a hydrological model even with only few gauges in a given catchment area.
Scale effect on runoff in alpine mountain catchments on China's Gongga Mountain
Authors: Lin Y. , Wang G. X.
Published: April 2010

Abstract. Finding an effective method to upscale or downscale hydrological processes is the central concern in hydrological research. The aim of this paper is to investigate a powerful, regulated relationship between runoff and catchment area, and establish the runoff scale transfer model for Gongga Mountain in China. We chose a series of catchments in which the contributing areas ranged from 0.41 km2 to 80.5 km2 to monitor the hydrological processes and meteorological conditions since 1990. To identify the nature and causes of variation in the runoff response to the size of catchments, a two-stage scaling method was proposed to describe the processes of runoff scaling. The results indicated that runoff had a different statistical relationship in different seasons and the related parameters were also different. The scaling models indicated a higher simulation efficiency and precision between the observed runoff and the calculated runoff, and they also provided a practical way for upscaling or downscaling in an alpine mountain watershed. For alpine mountain catchments, the results showed that the vegetation type and cover might be important factors for the runoff response to the scale effective.
A past discharges assimilation system for ensemble streamflow forecasts over France – Part 1: Description and validation of the assimilation system
Authors: Thirel G. , Martin E. , Mahfouf J.-F. , Massart S. , Ricci S. , Habets F.
Published: April 2010

Abstract. Two Ensemble Streamflow Prediction Systems (ESPSs) have been set up at Météo-France. They are based on the French SIM distributed hydrometeorological model. A deterministic analysis run of SIM is used to initialize the two ESPSs. In order to obtain a better initial state, a past discharges assimilation system has been implemented into this analysis SIM run, using the Best Linear Unbiased Estimator (BLUE). Its role is to improve the model soil moisture by using observed streamflows in order to better simulate streamflow. The skills of the assimilation system were assessed for a 569-day period on six different configurations, including two different physics schemes of the model (the use of an exponential profile of hydraulic conductivity or not) and, for each one, three different ways of considering the model soil moisture in the BLUE state variables. Respect of the linearity hypothesis of the BLUE was verified by assessing of the impact of iterations of the BLUE. The configuration including the use of the exponential profile of hydraulic conductivity and the combination of the moisture of the two soil layers in the state variable showed a significant improvement of streamflow simulations. It led to a significantly better simulation than the reference one, and the lowest soil moisture corrections. These results were confirmed by the study of the impacts of the past discharge assimilation system on a set of 49 independent stations.
Analysis of intra-country virtual water trade strategy to alleviate water scarcity in Iran
Authors: Faramarzi M. , Yang H. , Mousavi J. , Schulin R. , Binder C. R. , Abbaspour K. C.
Published: April 2010

Abstract. Increasing water scarcity has posed a major constraint to sustain food production in many parts of the world. To study the situation at the regional level, we took Iran as an example and analyzed how an intra-country "virtual water trade strategy" (VWTS) may help improve cereal production as well as alleviate the water scarcity problem. This strategy calls, in part, for the adjustment of the structure of cropping pattern (ASCP) and interregional food trade where crop yield and crop water productivity as well as local economic and social conditions are taken into account. We constructed a systematic framework to assess ASCP at the provincial level under various driving forces and constraints. A mixed-integer, multi-objective, linear optimization model was developed and solved by linear programming. Data from 1990–2004 were used to account for yearly fluctuations of water availability and food production. Five scenarios were designed aimed at maximizing the national cereal production while meeting certain levels of wheat self-sufficiency under various water and land constraints in individual provinces. The results show that under the baseline scenario, which assumes a continuation of the existing water use and food policy at the national level, some ASCP scenarios could produce more wheat with less water. Based on different scenarios in ASCP, we calculated that 31% to 100% of the total wheat shortage in the deficit provinces could be supplied by the wheat surplus provinces. As a result, wheat deficit provinces would receive 3.5 billion m3 to 5.5 billion m3 of virtual water by importing wheat from surplus provinces.
Evaluation of Penman-Monteith model applied to a maize field in the arid area of Northwest China
Authors: Zhao W.-Z. , Ji X.-B. , Kang E.-S. , Zhang Z.-H. , Jin B.-W.
Published: April 2010

Abstract. The Penman-Monteith (P-M) model has been applied to estimate evapotranspiration in terrestrial ecosystem widely in the world. As shown in many studies, bulk canopy resistance is an especially important factor in the application of P-M model. In this study, the authors used the Noilhan and Planton (N-P) approach and Jacobs and De Bruin (J-D) approach to express the bulk canopy resistance. The application of P-M mode to a maize field with two approaches in the arid area of Northwest China was evaluated by the measured half-hourly values from the eddy covariance system. The results indicate that the N-P approach underestimates slightly the bulk canopy resistance, while the J-D approach overestimates that. The estimation of bulk canopy resistance with N-P approach was then better and more consistent than that with J-D approach during the entire maize growing season. Correspondingly, the P-M model with J-D bulk canopy resistance slightly underestimated the latent heat flux throughout the maize growing season, but overestimated the latent heat flux during the dry period of the soil as compared to that with N-P approach. The good fitness of the simulated latent heat flux by the P-M model with N-P bulk canopy resistance approach to the measured one at a half-hour time step demonstrates the application of the approach is reasonable in the relative homogenous and not drought-stressed maize fields of the arid areas during the entire growing season. Further researches are discussed on enhancing the field observation, taking the correction for atmospheric stability into estimating aerodynamic resistance, to improve the performance of P-M model to simulate evapotranspiration in the cropped fields.
On the uncertainty of stream networks derived from elevation data: the error propagation approach
Authors: Hengl T. , Heuvelink G. B. M. , van Loon E. E.
Published: April 2010

Abstract. DEM error propagation methodology is extended to the derivation of vector-based objects (stream networks) using geostatistical simulations. First, point sampled elevations are used to fit a variogram model. Next 100 DEM realizations are generated using conditional sequential Gaussian simulation; the stream network map is extracted for each of these realizations, and the collection of stream networks is analyzed to quantify the error propagation. At each grid cell, the probability of the occurrence of a stream and the propagated error are estimated. The method is illustrated using two small data sets: Baranja hill (30 m grid cell size; 16 512 pixels; 6367 sampled elevations), and Zlatibor (30 m grid cell size; 15 000 pixels; 2051 sampled elevations). All computations are run in the open source software for statistical computing R: package geoR is used to fit variogram; package gstat is used to run sequential Gaussian simulation; streams are extracted using the open source GIS SAGA via the RSAGA library. The resulting stream error map (Information entropy of a Bernoulli trial) clearly depicts areas where the extracted stream network is least precise – usually areas of low local relief, slightly concave. In both cases, significant parts of the study area (17.3% for Baranja Hill; 6.2% for Zlatibor) show high error (H>0.5) of locating streams. By correlating the propagated uncertainty of the derived stream network with various land surface parameters sampling of height measurements can be optimized so that delineated streams satisfy a required accuracy level. Remaining issue to be tackled is the computational burden of geostatistical simulations: this framework is at the moment limited to small to moderate data sets with several hundreds of points. Scripts and data sets used in this article are available on-line via the http://www.geomorphometry.org/ website and can be easily adopted/adjusted to any similar case study.
Influence of cracking clays on satellite observed and model simulated soil moisture
Authors: Liu Y. Y. , McCabe M. F. , Evans J. P. , van Dijk A. I. J. M. , de Jeu R. A. M. , Su H.
Published: April 2010

Abstract. Vertisols are clay soils that are common in the monsoonal and dry warm regions of the world. A defining feature of these soils is the development of shrinking cracks during dry periods, the effects of which are not described in land surface models nor considered in the surface soil moisture estimation from passive microwave satellite observations. To investigate the influence of this process we compared the soil moisture (θ in m3 m−3) from AMSR-E observations and the Community Land Model (CLM) simulations over vertisols across mainland Australia. Both products agree reasonably well during wet seasons. However, during dry periods, AMSR-E θ falls below values for surrounding non-clays, while CLM simulations are higher. The impacts of soil property used in the AMSR-E algorithm, vegetation density and rainfall patterns were investigated, but do not explain the observed θ patterns. Analysis of the retrieval model suggests that the most likely reason for the low AMSR-E θ is the increase in soil porosity and surface roughness through cracking. CLM does not consider the behavior of cracking clay, including the further loss of moisture from soil and extremely high infiltration rates that would occur when cracks develop. Analyses show that the corresponding water fluxes can be different when cracks occur and therefore modeled evaporation, surface temperature, surface runoff and groundwater recharge should be interpreted with caution. Introducing temporally dynamic roughness and soil porosity into retrieval algorithms and adding a "cracking clay" module into models, respectively, may improve the representation of vertisol hydrology.
Simulation of the snowmelt runoff contributing area in a small alpine basin
Authors: DeBeer C. M. , Pomeroy J. W.
Published: April 2010

Abstract. Simulation of areal snowmelt and snow-cover depletion over time can be carried out by applying point-scale melt rate computations to distributions of snow water equivalent (SWE). In alpine basins, this can be done by considering these processes separately on individual slope units. However, differences in melt timing and rates arise at smaller spatial scales due to the variability in SWE and snowpack cold content, which affects the timing of melt initiation, depletion of the snow-cover and spatial extent of the snowmelt runoff contributing area (SRCA). This study examined the effects of variability in SWE, internal energy and applied melt energy on melt rates and timing, and snow-cover depletion in a small cold regions alpine basin over various scales ranging from point to basin. Melt rate computations were performed using a physically based energy balance snowmelt routine (Snobal) in the Cold Regions Hydrological Model (CRHM) and compared with measurements at three meteorological stations over a ridge within the basin. At the point scale, a negative association between daily melt rates and SWE was observed in the early melt period, with deeper snow requiring greater energy inputs to initiate melt. SWE distributions over the basin (stratified by slope) were measured using snow surveys and repeat LiDAR depth estimates, and used together with computed melt rates to simulate the areal snow-cover depletion. Comparison with observations from georeferenced oblique photographs showed an improvement in simulated areal snow-cover depletion curves when accounting for the variability in melt rate with depth of SWE in the early melt period. Finally, the SRCA was characterized as the product of the snow-covered area and the fraction of the SWE distribution undergoing active melt on each slope unit. Results for each slope were then aggregated to give the basin scale SRCA. The SRCA is controlled by the variability of melt amongst slope units and over individual SWE distributions, the variability of SWE and the resulting snow-cover depletion patterns over the basin.
Morphotectonic properties of the Lo River Fault near Tam Dao in North Vietnam
Authors: Cuong N. Q. , Zuchiewicz W. A.
Published: April 2010

Abstract. The Lo River fault near Tam Dao, North Vietnam, is a young, right-lateral, normal fault which has been active throughout the Quaternary. Rates of dextral slip range between 1 and 2 mm/yr whereas rates of uplift can be estimated roughly at 0.1–1 mm/yr. The drainage deflection and arrangement of shutter ridges suggest 1.5–2.0 km of dextral offset during the past 1–2 millions of years (m. y.), and the height of the youngest faceted spurs averages at 170 m. Analysis of morphometric parametres of the mountain front at Tam Dao indicates that this segment shows properties typical for nearly rectilinear, young normal scarps that belong to class I or II of relative tectonic activity and that are capable of generating strong earthquakes in the future.
Tsunami waveform inversion by numerical finite-elements Green’s functions
Authors: Piatanesi A. , Tinti S. , Pagnoni G.
Published: April 2010

Abstract. During the last few years, the steady increase in the quantity and quality of the data concerning tsunamis has led to an increasing interest in the inversion problem for tsunami data. This work addresses the usually ill-posed problem of the hydrodynamical inversion of tsunami tide-gage records to infer the initial sea perturbation. We use an inversion method for which the data space consists of a given number of waveforms and the model parameter space is represented by the values of the initial water elevation field at a given number of points. The forward model, i.e. the calculation of the synthetic tide-gage records from an initial water elevation field, is based on the linear shallow water equations and is simply solved by applying the appropriate Green’s functions to the known initial state. The inversion of tide-gage records to determine the initial state results in the least square inversion of a rectangular system of linear equations. When the inversions are unconstrained, we found that in order to attain good results, the dimension of the data space has to be much larger than that of the model space parameter. We also show that a large number of waveforms is not sufficient to ensure a good inversion if the corresponding stations do not have a good azimuthal coverage with respect to source directivity. To improve the inversions we use the available a priori information on the source, generally coming from the inversion of seismological data. In this paper we show how to implement very common information about a tsunamigenic seismic source, i.e. the earthquake source region, as a set of spatial constraints. The results are very satisfactory, since even a rough localisation of the source enables us to invert correctly the initial elevation field.
Detecting premonitory seismicity patterns based on critical point dynamics
Authors: Zöller G. , Hainzl S.
Published: April 2010

Abstract. We test the hypothesis that critical point dynamics precedes strong earthquakes in a region surrounding the future hypocenter. Therefore, we search systematically for regions obeying critical point dynamics in terms of a growing spatial correlation length (GCL). The question of whether or not these spatial patterns are correlated with future seismicity is crucial for the problem of predictability. The analysis is conducted for earthquakes with M > 6.5 in California. As a result, we observe that GCL patterns are correlated with the distribution of future seismicity. In particular, there are clear correlations in some cases, e.g. the 1989 Loma Prieta earthquake and the 1999 Hector Mine earthquake. We claim that the critical point concept can improve the seismic hazard assessment.
Brief communication "Models for the exceedances of high thresholds over the precipitation daily totals in Athens, Greece"
Authors: Tzavelas G. , Paliatsos A. G. , Nastos P. T.
Published: April 2010

Abstract. Extreme precipitation events have significant environmental consequences because they may cause considerable damages to urban as well as rural areas. The aim of this work is to construct a threshold model which will describe the exceedances over a threshold for the daily precipitation totals over Athens, Greece. The data used are daily precipitation totals recorded at the National Observatory of Athens, for a 115-year period (1891–2005). The generalized Pareto distribution is considered as the proper distribution for the study of the exceedances. The threshold of u=15.8 mm (10% upper limit) is used for the construction of the optimal return level function.
A reflection about the social and technological aspects in flood risk management – the case of the Italian Civil Protection
Authors: del Carmen Llasat M. , Siccardi F.
Published: April 2010

Abstract. The right of a person to be protected from natural hazards is a characteristic of the social and economical development of the society. This paper is a contribution to the reflection about the role of Civil Protection organizations in a modern society. The paper is based in the inaugural conference made by the authors on the 9th Plinius Conference on Mediterranean Storms. Two major issues are considered. The first one is sociological; the Civil Protection organizations and the responsible administration of the land use planning should be perceived as reliable as possible, in order to get consensus on the restrictions they pose, temporary or definitely, on the individual free use of the territory as well as in the entire warning system. The second one is technological: in order to be reliable they have to issue timely alert and warning to the population at large, but such alarms should be as "true" as possible. With this aim, the paper summarizes the historical evolution of the risk assessment, starting from the original concept of "hazard", introducing the concepts of "scenario of event" and "scenario of risk" and ending with a discussion about the uncertainties and limits of the most advanced and efficient tools to predict, to forecast and to observe the ground effects affecting people and their properties. The discussion is centred in the case of heavy rains and flood events in the North-West of Mediterranean Region.
Time-dependent Z-R relationships for estimating rainfall fields from radar measurements
Authors: Alfieri L. , Claps P. , Laio F.
Published: April 2010

Abstract. The operational use of weather radars has become a widespread and useful tool for estimating rainfall fields. The radar-gauge adjustment is a commonly adopted technique which allows one to reduce bias and dispersion between radar rainfall estimates and the corresponding ground measurements provided by rain gauges. This paper investigates a new methodology for estimating radar-based rainfall fields by recalibrating at each time step the reflectivity-rainfall rate (Z-R) relationship on the basis of ground measurements provided by a rain gauge network. The power-law equation for converting reflectivity measurements into rainfall rates is readjusted at each time step, by calibrating its parameters using hourly Z-R pairs collected in the proximity of the considered time step. Calibration windows with duration between 1 and 24 h are used for estimating the parameters of the Z-R relationship. A case study pertaining to 19 rainfall events occurred in the north-western Italy is considered, in an area located within 25 km from the radar site, with available measurements of rainfall rate at the ground and radar reflectivity aloft. Results obtained with the proposed method are compared to those of three other literature methods. Applications are described for a posteriori evaluation of rainfall fields and for real-time estimation. Results suggest that the use of a calibration window of 2–5 h yields the best performances, with improvements that reach the 28% of the standard error obtained by using the most accurate fixed (climatological) Z-R relationship.
On analysing sea level rise in the German Bight since 1844
Authors: Wahl T. , Jensen J. , Frank T.
Published: April 2010

Abstract. In this paper, a methodology to analyse observed sea level rise (SLR) in the German Bight, the shallow south-eastern part of the North Sea, is presented. The paper focuses on the description of the methods used to generate and analyse mean sea level (MSL) time series. Parametric fitting approaches as well as non-parametric data adaptive filters, such as Singular System Analysis (SSA) are applied. For padding non-stationary sea level time series, an advanced approach named Monte-Carlo autoregressive padding (MCAP) is introduced. This approach allows the specification of uncertainties of the behaviour of smoothed time series near the boundaries. As an example, the paper includes the results from analysing the sea level records of the Cuxhaven tide gauge and the Heligoland tide gauge, both located in the south-eastern North Sea. For comparison, the results from analysing a worldwide sea level reconstruction are also presented. The results for the North Sea point to a weak negative acceleration of SLR since 1844 with a strong positive acceleration at the end of the 19th century, to a period of almost no SLR around the 1970s with subsequent positive acceleration and to high recent rates.
Rockslide deformation monitoring with fiber optic strain sensors
Authors: Moore J. R. , Gischig V. , Button E. , Loew S.
Published: April 2010

Abstract. With micro-strain resolution and the capability to sample at rates of 100 Hz and higher, fiber optic (FO) strain sensors offer exciting new possibilities for in-situ landslide monitoring. Here we describe a new FO monitoring system based on long-gauge fiber Bragg grating sensors installed at the Randa Rockslide Laboratory in southern Switzerland. The new FO monitoring system can detect sub-micrometer scale deformations in both triggered-dynamic and continuous measurements. Two types of sensors have been installed: (1) fully embedded borehole sensors and (2) surface extensometers. Dynamic measurements are triggered by sensor deformation and recorded at 100 Hz, while continuous data are logged every 5 min. Deformation time series for all sensors show displacements consistent with previous monitoring. Accelerated shortening following installation of the borehole sensors is likely related to long-term shrinkage of the grout. A number of transient signals have been observed, which in some cases were large enough to trigger rapid sampling. The combination of short- and long-term observation offers new insight into the deformation process. Accelerated surface crack opening in spring is shown to have a diurnal trend, which we attribute to the effect of snowmelt seeping into the crack void space and freezing at night to generate pressure on the crack walls. Controlled-source tests investigated the sensor response to dynamic inputs, which compared an independent measure of ground motion against the strain measured across a surface crack. Low frequency signals were comparable but the FO record suffered from aliasing, where undersampling of higher frequency signals generated spectral peaks not related to ground motion.
Persistent pre-seismic signature detected by means of Na-K-Mg geothermometry records in a saline spring of Vrancea area (Romania)
Authors: Mitrofan H. , Marin C. , Zugrăvescu D. , Chitea F. , Anghelache M.-A. , Beşuţiu L. , Tudorache A.
Published: April 2010

Abstract. A six year-long hydrochemical monitoring operation was conducted in Vrancea seismic zone (Romania), addressing a saline spring that proved to be suitable for Na-K-Mg geothermometry diagnosis. During the considered time-interval (2003–2009), only one important earthquake (mb=5.8) occurred in Vrancea region, this circumstance providing an unambiguous reference-moment between pre-seismic and post-seismic periods. On occurrence of that earthquake, an anomalous fluctuation of the Na-K temperature was detected – a result largely similar to previous ones recorded worldwide (California, southwest Egypt, northeast India). Yet such fluctuations may not necessarily be induced by earthquake-associated processes: they can occur also "routinely", possibly reflecting some environmental, meteorologically-induced "noise". It was therefore important to examine whether the variations observed in the data values could be plausibly related to a seismogenesis process. By additionally investigating (in a "scattterplot" diagram) the correlation between the Na-K temperatures and the values of a so-called "maturity index", a specific pattern emerged, with pre-seismic data-points plotting in a distinct domain of the diagram; moreover, those data-points appeared to describe a "drift away" pathway with respect to the remaining data-points "cluster", recorded during the subsequent 4 years of post-seismic monitoring. The "drift away" pattern persistently evolved for at least 18 months, ending just before the mb=5.8 earthquake and consequently suggesting the existence of some kind of long-term precursory phenomenon.
Unfolding the procedure of characterizing recorded ultra low frequency, kHZ and MHz electromagnetic anomalies prior to the L'Aquila earthquake as pre-seismic ones - Part 2
Authors: Eftaxias K. , Balasis G. , Contoyiannis Y. , Papadimitriou C. , Kalimeri M. , Athanasopoulou L. , Nikolopoulos S. , Kopanas J. , Antonopoulos G. , Nomicos C.
Published: April 2010

Abstract. Ultra low frequency-ULF (1 Hz or lower), kHz and MHz electromagnetic (EM) anomalies were recorded prior to the L'Aquila catastrophic earthquake (EQ) that occurred on 6 April 2009. The detected anomalies followed this temporal scheme. (i) The MHz EM anomalies were detected on 26 March 2009 and 2 April 2009. The kHz EM anomalies were emerged on 4 April 2009. The ULF EM anomaly was appeared from 29 March 2009 up to 3 April 2009. The question effortlessly arises as to whether the observed anomalies before the L'Aquila EQ were seismogenic or not. The main goal of this work is to provide some insight into this issue. More precisely, the main aims of this contribution are threefold: How can we recognize an EM observation as pre-seismic one? We aim, through a multidisciplinary analysis to provide some elements of a definition. How can we link an individual EM anomaly with a distinctive stage of the EQ preparation process? The present analysis is consistent with the hypothesis that the kHz EM anomalies were associated with the fracture of asperities that were distributed along the L'Aquila fault sustaining the system, while the MHz EM anomalies could be triggered by fractures in the highly disordered system that surrounded the backbone of asperities of the activated fault. How can we identify precursory symptoms in an individual EM precursor that indicate that the occurrence of the EQ is unavoidable? We clearly state that the detection of a MHz EM precursor does not mean that the occurrence of EQ is unavoidable; the abrupt emergence of kHz EM emissions indicate the fracture of asperities. The observed ULF EM anomaly supports the hypothesis of a relationship between processes produced by increasing tectonic stresses in the Earth's crust and attendant EM interactions between the crust and ionosphere. We emphasize that we attempt to specify not only whether or not a single EM anomaly is pre-seismic in itself, but mainly whether a combination of emergent ULF, MHz and kHz EM anomalies could be characterized as pre-earthquake.
Brief communication "Does climatic change in precipitation drive erosion in Naxos Island, Greece?"
Authors: Nastos P. T. , Evelpidou N. , Vassilopoulos A.
Published: April 2010

Abstract. In this paper we examined whether the recorded precipitation changes cause erosion in Naxos Island, Greece using precipitation indices derived from daily precipitation totals, during the period 1955–2007, in order to develop an erosion risk model. Although the mean annual precipitation appear to be low (~360.0 mm), the erosion processes of the area are very intense, because of the intensive character of precipitation, the high slope relief, the differential lithology and the absence of important land cover The results of the analysis showed that the climatic changes in precipitation and the changes in land cover and land use are the main drivers for the erosion. This is why the 2nd (1971–1985) and 3rd (1986–2007) studied sub-periods may be called of high erosion risk, and especially the second one mainly because of the increased frequency of extreme precipitation events.
A study on the Abruzzo 6 April 2009 earthquake by applying the RST approach to 15 years of AVHRR TIR observations
Authors: Lisi M. , Filizzola C. , Genzano N. , Grimaldi C. S. L. , Lacava T. , Marchese F. , Mazzeo G. , Pergola N. , Tramutoli V.
Published: April 2010

Abstract. A self adaptive approach (RST, Robust Satellite Technique) has been proposed as a suitable tool for satellite TIR surveys in seismically active regions devoted to detect and monitor thermal anomalies possibly related to earthquake occurrence. In this work, RST approach has been applied to 15 years of AVHRR (Advanced Very High Resolution Radiometer) thermal infrared observations in order to study the 6 April 2009 Abruzzo earthquake. Preliminary results show clear differences in TIR anomalies occurrence during the periods used for validation (15 March–15 April 2009) and the one (15 March–15 April 2008) without earthquakes with ML≥4.5, used for confutation purposes. Quite clear TIR anomalies appears also to mark main tectonic lineaments during the preparatory phases of others, low magnitude(3.9
People living under threat of volcanic hazard in southern Iceland: vulnerability and risk perception
Authors: Jóhannesdóttir G. , Gísladóttir G.
Published: April 2010

Abstract. Residents in the village of Vík and in the farming community of Álftaver in southern Iceland are living with the threat of volcanic hazards. The highly active subglacial volcano Katla has erupted approximately twice per century since the beginning of settlement around 874 AD. The last major eruption was in 1918 and Katla has recently entered an agitated stage. The purpose of this research was to (1) review residents' responses in relation to vulnerability, (2) examine their risk perception, preparedness and mitigation in relation to an eruption of Katla, and (3) investigate the public and the representative of the local authorities and emergency manager's knowledge of the official evacuation plan. In 2004, we conducted in-depth, face-to-face interviews with local residents using a snowball sample technique. All participants were permanent residents of the two communities, between the ages of 25–95 and most had lived in the area their entire lives. Regardless of the residents' knowledge about past volcanic activity of Katla and the associated future risk, many residents were doubtful about the imminent eruption forecast by scientists and they believed that the volcano is no longer active. In both communities, different social, cultural and economic factors played a central role in how people perceived natural hazards and how they dealt with the fact that their lives and livelihoods could be at risk. The participants had good knowledge about the existing evacuation plan and had participated in evacuation exercises. However, they had not made personal mitigation or preparedness plans in the event of a future eruption. In contrast to the residents of Vík, the inhabitants in Álftaver are concerned about the evacuation process and found it very confusing; they neither found the emergency plan nor the proposed methods for risk communication relevant for their farming community. The perception of the inhabitants, especially in Álftaver, does not correspond to those tasked with the responsibility of developing the emergency and evacuation plans. In order to ensure the safety of all concerned, better cooperation, mutual understanding and adequate communication between the scientific community, governmental and local authorities and the inhabitants is necessary.
Rainfall thresholds for the possible occurrence of landslides in Italy
Authors: Brunetti M. T. , Peruccacci S. , Rossi M. , Luciani S. , Valigi D. , Guzzetti F.
Published: April 2010

Abstract. In Italy, rainfall is the primary trigger of landslides that frequently cause fatalities and large economic damage. Using a variety of information sources, we have compiled a catalogue listing 753 rainfall events that have resulted in landslides in Italy. For each event in the catalogue, the exact or approximate location of the landslide and the time or period of initiation of the slope failure is known, together with information on the rainfall duration D, and the rainfall mean intensity I, that have resulted in the slope failure. The catalogue represents the single largest collection of information on rainfall-induced landslides in Italy, and was exploited to determine the minimum rainfall conditions necessary for landslide occurrence in Italy, and in the Abruzzo Region, central Italy. For the purpose, new national rainfall thresholds for Italy and new regional rainfall thresholds for the Abruzzo Region were established, using two independent statistical methods, including a Bayesian inference method and a new Frequentist approach. The two methods proved complementary, with the Bayesian method more suited to analyze small data sets, and the Frequentist method performing better when applied to large data sets. The new regional thresholds for the Abruzzo Region are lower than the new national thresholds for Italy, and lower than the regional thresholds proposed in the literature for the Piedmont and Lombardy Regions in northern Italy, and for the Campania Region in southern Italy. This is important, because it shows that landslides in Italy can be triggered by less severe rainfall conditions than previously recognized. The Frequentist method experimented in this work allows for the definition of multiple minimum rainfall thresholds, each based on a different exceedance probability level. This makes the thresholds suited for the design of probabilistic schemes for the prediction of rainfall-induced landslides. A scheme based on four probabilistic thresholds is proposed. The four thresholds separate five fields, each characterized by different rainfall intensity-duration conditions, and corresponding different probability of possible landslide occurrence. The scheme can be implemented in landslide warning systems that operate on rainfall thresholds, and on precipitation measurements or forecasts.