iudad Visible versus ciudad invisible: la gestión del riesgo por inundaciones en la ciudad de Buenos Aires.

Floods are the main risk of natural origin in the city of Buenos Aires. Although they are originated by intense rainfall or level rising of the Río de la plata, the complex network of urban actions and decisions has amplied the treta and the natural hydric system has become a technological one.

Gestión del riesgo de desastres en el contexto de la Ola Invernal 2010-2011. Estudio de caso municipio de Campo de la Cruz, Atlántico.

El objetivo de este estudio de caso es analizar los procesos de gestión del riesgo de desastres por inundación en el municipio de Campo de la Cruz, al sur del Atlántico, en el contexto de la ola invernal 2010-2011. La ruptura del Canal del Dique, el 30 de diciembre de 2010, implicó la entrada de una gran cantidad de agua al departamento del Atlántico, afectando el 100% del municipio. La normativa colombiana en materia de gestión del riesgo de desastres es reciente, de ahí que su aplicación se haya producido efectivamente con el fenómeno a estudiar en este trabajo. Así, se identifican aquellas características del ordenamiento municipal y de la ola invernal para después analizar sus efectos sobre el municipio. Las inundaciones afectaron tanto a la población como al territorio, especialmente porque éste no estaba preparado ni contaba con las suficientes herramientas para mitigar los riesgos. En este sentido, el presente trabajo identifica los instrumentos de planificación y gestión que permiten consolidar la gestión del riesgo de desastres como una política de estado ligada a lo territorial, pero al mismo tiempo desde una perspectiva integral en la que predomine el enfoque preventivo más que el reactivo.

Desafíos y oportunidades de la capacidad del gobierno colombiano en la implementación de la política pública de gestión integral del riesgo (ley 1523 de 2012)

La geografía colombiana es fuente de un sinnúmero de recursos socio-económicos y naturales así como también de amenazas a la población, ya que es un territorio propenso a ciertos fenómenos que desencadenan desastres, como inundaciones, deslizamientos, sismos, etc. Sin embargo, el Estado tiene una inmensa responsabilidad en la mitigación del riesgo de desastres que sufre la ciudadanía, pero las instituciones no han tenido la fortaleza para implementar políticas públicas eficientes que eviten que el impacto de estos fenómenos sea mayor. La presente monografía es un estudio de las políticas públicas en materia de desastres implementadas por el Estado, tomando como base los postulados del neo-institucionalismo y la teoría de Levitsky y Murillo sobre la fortaleza de las instituciones, reflejando una baja estabilidad y fuerza de implementación.

Els Barris de Sant Narcís i de Santa Eugènia davant les avingudes del Güell

Les obres d’acondicionament i millora del riu Güell passen per dues fases. La primera, fins al 1971, demostren que el problema no estava ni de bon tros solucionat, més fruit de la improvisació i poca lògica de l’Administració que d'una bona política de planificació hidràulica. Les obres mes recents, (transvasament Güell-Marroc. Massanas-Ter), aparentment solucionen el problema. Però cal insistir un cop més; d'ençà el 1970 i fins avui dia, el riu Güell no ha sofert cap més avinguda important, si bé és cert que Girona no n'ha patit cap d’aquelles dimensions. Com passa en la majoria dels casos, el risc d'avingudes és un fantasma que ve de la mateixa manera que se'n va, que dura l’escàs període de l'avinguda i els dies-mesos que segueixen

Requalificação Urbana e Infraestruturas Hidráulicas

This article focuses on issues of planning that arise in S Vicente Island and in particular in the city of MindeloWe consider issues of urban regeneration and the inventory of solutions within the general scope of hydraulic options solutions for an appropriate response to the serious problems caused by floods in Mindelo, which occur at times of heavy rainfall.

Inundações urbanas na vila de Arouca : organização do escoamento superficial e áreas suscetíveis

As inundações urbanas, embora sejam um tema pouco estudado em Portugal, são um reflexo da intensificação da urbanização do território, facto que se tem acentuado no país (Oliveira, 2003). Com efeito, o objetivo deste artigo é compreender a dinâmica do escoamento superficial na área urbanizada da Vila de Arouca, mediante a identificação e análise do contributo que os elementos da malha urbana desempenham em todo esse processo. Por outro lado, analisa-se a evolução dos usos do solo nas últimas décadas, de forma a entender os efeitos que o incremento de áreas impermeabilizadas teve no reforço da componente superficial do escoamento. O inventário realizado sobre o escoamento superficial conduzido pelas vias da malha urbana, possibilitou a determinação dos locais mais problemáticos na área da vila e dos elementos expostos a este tipo de ocorrência. Assim, o estudo constitui um contributo para o ordenamento do território do município de Arouca, essencialmente, pela abordagem metodológica apresentada e pelos resultados obtidos.

Calibration of uncertain flood inundation models using remotely sensed water levels

A traditional method of validating the performance of a flood model when remotely sensed data of the flood extent are available is to compare the predicted flood extent to that observed. The performance measure employed often uses areal pattern-matching to assess the degree to which the two extents overlap. Recently, remote sensing of flood extents using synthetic aperture radar (SAR) and airborne scanning laser altimetry (LIDAR) has made more straightforward the synoptic measurement of water surface elevations along flood waterlines, and this has emphasised the possibility of using alternative performance measures based on height. This paper considers the advantages that can accrue from using a performance measure based on waterline elevations rather than one based on areal patterns of wet and dry pixels. The two measures were compared for their ability to estimate flood inundation uncertainty maps from a set of model runs carried out to span the acceptable model parameter range in a GLUE-based analysis. A 1 in 5-year flood on the Thames in 1992 was used as a test event. As is typical for UK floods, only a single SAR image of observed flood extent was available for model calibration and validation. A simple implementation of a two-dimensional flood model (LISFLOOD-FP) was used to generate model flood extents for comparison with that observed. The performance measure based on height differences of corresponding points along the observed and modelled waterlines was found to be significantly more sensitive to the channel friction parameter than the measure based on areal patterns of flood extent. The former was able to restrict the parameter range of acceptable model runs and hence reduce the number of runs necessary to generate an inundation uncertainty map. A result of this was that there was less uncertainty in the final flood risk map. The uncertainty analysis included the effects of uncertainties in the observed flood extent as well as in model parameters. The height-based measure was found to be more sensitive when increased heighting accuracy was achieved by requiring that observed waterline heights varied slowly along the reach. The technique allows for the decomposition of the reach into sections, with different effective channel friction parameters used in different sections, which in this case resulted in lower r.m.s. height differences between observed and modelled waterlines than those achieved by runs using a single friction parameter for the whole reach. However, a validation of the modelled inundation uncertainty using the calibration event showed a significant difference between the uncertainty map and the observed flood extent. While this was true for both measures, the difference was especially significant for the height-based one. This is likely to be due to the conceptually simple flood inundation model and the coarse application resolution employed in this case. The increased sensitivity of the height-based measure may lead to an increased onus being placed on the model developer in the production of a valid model

Subseasonal extremes of precipitation and active-break cycles of the Indian summer monsoon in a climate-change scenario

Changes to the behaviour of subseasonal precipitation extremes and active-break cycles of the Indian summer monsoon are assessed in this study using pre-industrial and 2 × CO2 integrations of the Hadley Centre coupled model HadCM3, which is able to simulate the monsoon seasonal cycle reasonably. At 2 × CO2, mean summer rainfall increases slightly, especially over central and northern India. The mean intensity of daily precipitation during the monsoon is found to increase, consistent with fewer wet days, and there are increases to heavy rain events beyond changes in the mean alone. The chance of reaching particular thresholds of heavy rainfall is found to approximately double over northern India, increasing the likelihood of damaging floods on a seasonal basis. The local distribution of such projections is uncertain, however, given the large spread in mean monsoon rainfall change and associated extremes amongst even the most recent coupled climate models. The measured increase of the heaviest precipitation events over India is found to be broadly in line with the degree of atmospheric warming and associated increases in specific humidity, lending a degree of predictability to changes in rainfall extremes. Active-break cycles of the Indian summer monsoon, important particularly due to their effect on agricultural output, are shown to be reasonably represented in HadCM3, in particular with some degree of northward propagation. We note an intensification of both active and break events, particularly when measured against the annual cycle, although there is no suggestion of any change to the duration or likelihood of monsoon breaks. Copyright © 2009 Royal Meteorological Society

Floodplain environmental change during the Younger Dryas and Holocene in Northwest Europe: Insights from the lower Kennet Valley, south central England

Many lowland rivers across northwest Europe exhibit broadly similar behavioural responses to glacial-interglacial transitions and landscape development. Difficulties exist in assessing these, largely because the evidence from many rivers remains limited and fragmentary. Here we address this issue in the context of the river Kennet, a tributary of the Thames, since c. 13,000 cal BP. Some similarities with other rivers are present, suggesting that regional climatic shifts are important controls. The Kennet differs from the regional pattern in a number of ways. The rate of response to sudden climatic change, particularly at the start of the Holocene and also mid-Holocene forest clearance, appears very high. This may reflect abrupt shifts between two catchment scale hydrological states arising from contemporary climates, land use change and geology. Stadial hydrology is dominated by nival regimes, with limited winter infiltration and high spring and summer runoff. Under an interglacial climate, infiltration is more significant. The probable absence of permafrost in the catchment means that a lag between the two states due to its gradual decay is unlikely. Palaeoecology, supported by radiocarbon dates, suggests that, at the very start of the Holocene, a dramatic episode of fine sediment deposition across most of the valley floor occurred, lasting 500-1000 years. A phase of peat accumulation followed as mineral sediment supply declined. A further shift led to tufa deposition, initially in small pools, then across the whole floodplain area, with the river flowing through channels cut in tufa and experiencing repeated avulsion. Major floods, leaving large gravel bars that still form positive relief features on the floodplain, followed mid-Holocene floodplain stability. Prehistoric deforestation is likely to be the cause of this flooding, inducing a major environmental shift with significantly increased surface runoff. Since the Bronze Age, predominantly fine sediments were deposited along the valley with apparently stable channels and vertical floodplain accretion associated with soil erosion and less catastrophic flooding. The Kennet demonstrates that, while a general pattern of river behaviour over time, within a region, may be identifiable, individual rivers are likely to diverge from this. Consequently, it is essential to understand catchment controls, particularly the relative significance of surface and subsurface hydrology. (c) 2005 Elsevier B.V. All rights reserved.

Uses of airborne scanning laser altimetry for river flood modelling and coastal geomorphology

Two ongoing projects at ESSC that involve the development of new techniques for extracting information from airborne LiDAR data and combining this information with environmental models will be discussed. The first project in conjunction with Bristol University is aiming to improve 2-D river flood flow models by using remote sensing to provide distributed data for model calibration and validation. Airborne LiDAR can provide such models with a dense and accurate floodplain topography together with vegetation heights for parameterisation of model friction. The vegetation height data can be used to specify a friction factor at each node of a model’s finite element mesh. A LiDAR range image segmenter has been developed which converts a LiDAR image into separate raster maps of surface topography and vegetation height for use in the model. Satellite and airborne SAR data have been used to measure flood extent remotely in order to validate the modelled flood extent. Methods have also been developed for improving the models by decomposing the model’s finite element mesh to reflect floodplain features such as hedges and trees having different frictional properties to their surroundings. Originally developed for rural floodplains, the segmenter is currently being extended to provide DEMs and friction parameter maps for urban floods, by fusing the LiDAR data with digital map data. The second project is concerned with the extraction of tidal channel networks from LiDAR. These networks are important features of the inter-tidal zone, and play a key role in tidal propagation and in the evolution of salt-marshes and tidal flats. The study of their morphology is currently an active area of research, and a number of theories related to networks have been developed which require validation using dense and extensive observations of network forms and cross-sections. The conventional method of measuring networks is cumbersome and subjective, involving manual digitisation of aerial photographs in conjunction with field measurement of channel depths and widths for selected parts of the network. A semi-automatic technique has been developed to extract networks from LiDAR data of the inter-tidal zone. A multi-level knowledge-based approach has been implemented, whereby low level algorithms first extract channel fragments based mainly on image properties then a high level processing stage improves the network using domain knowledge. The approach adopted at low level uses multi-scale edge detection to detect channel edges, then associates adjacent anti-parallel edges together to form channels. The higher level processing includes a channel repair mechanism.

A baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change

This report forms part of a larger research programme on 'Reinterpreting the Urban-Rural Continuum', which conceptualises and investigates current knowledge and research gaps concerning 'the role that ecosystems services play in the livelihoods of the poor in regions undergoing rapid change'. The report aims to conduct a baseline appraisal of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. The appraisal is conducted at three spatial scales: global, regional (four consortia areas), and meso scale (case studies within the four regions). At all three scales of analysis water resources form the interweaving theme because water provides a vital provisioning service for people, supports all other ecosystem processes and because water resources are forecast to be severely affected under climate change scenarios. This report, combined with an Endnote library of over 1100 scientific papers, provides an annotated bibliography of water-dependant ecosystem services, the roles they play within desakota livelihood systems and their potential sensitivity to climate change. After an introductory, section, Section 2 of the report defines water-related ecosystem services and how these are affected by human activities. Current knowledge and research gaps are then explored in relation to global scale climate and related hydrological changes (e.g. floods, droughts, flow regimes) (section 3). The report then discusses the impacts of climate changes on the ESPA regions, emphasising potential responses of biomes to the combined effects of climate change and human activities (particularly land use and management), and how these effects coupled with water store and flow regime manipulation by humans may affect the functioning of catchments and their ecosystem services (section 4). Finally, at the meso-scale, case studies are presented from within the ESPA regions to illustrate the close coupling of human activities and catchment performance in the context of environmental change (section 5). At the end of each section, research needs are identified and justified. These research needs are then amalgamated in section 6.

Improvement of link failure restoration utilising MPLS as a means to maintain QoS

The availability of a network strongly depends on the frequency of service outages and the recovery time for each outage. The loss of network resources includes complete or partial failure of hardware and software components, power outages, scheduled maintenance such as software and hardware, operational errors such as configuration errors and acts of nature such as floods, tornadoes and earthquakes. This paper proposes a practical approach to the enhancement of QoS routing by means of providing alternative or repair paths in the event of a breakage of a working path. The proposed scheme guarantees that every Protected Node (PN) is connected to a multi-repair path such that no further failure or breakage of single or double repair paths can cause any simultaneous loss of connectivity between an ingress node and an egress node. Links to be protected in an MPLS network are predefined and an LSP request involves the establishment of a working path. The use of multi-protection paths permits the formation of numerous protection paths allowing greater flexibility. Our analysis will examine several methods including single, double and multi-repair routes and the prioritization of signals along the protected paths to improve the Quality of Service (QoS), throughput, reduce the cost of the protection path placement, delay, congestion and collision.

The transformation of earth-system observations into information of socio-economic value in GEOSS

The Group on Earth Observations System of Systems, GEOSS, is a co-ordinated initiative by many nations to address the needs for earth-system information expressed by the 2002 World Summit on Sustainable Development. We discuss the role of earth-system modelling and data assimilation in transforming earth-system observations into the predictive and status-assessment products required by GEOSS, across many areas of socio-economic interest. First we review recent gains in the predictive skill of operational global earth-system models, on time-scales of days to several seasons. We then discuss recent work to develop from the global predictions a diverse set of end-user applications which can meet GEOSS requirements for information of socio-economic benefit; examples include forecasts of coastal storm surges, floods in large river basins, seasonal crop yield forecasts and seasonal lead-time alerts for malaria epidemics. We note ongoing efforts to extend operational earth-system modelling and assimilation capabilities to atmospheric composition, in support of improved services for air-quality forecasts and for treaty assessment. We next sketch likely GEOSS observational requirements in the coming decades. In concluding, we reflect on the cost of earth observations relative to the modest cost of transforming the observations into information of socio-economic value.

Exploring NOy chemistry in levitated aqueous aerosol droplets

Chemistry of reactive nitrogen oxides, NOy, is crucial for our understanding of composition and properties of the Earth’s atmosphere. The proof-of-principle experiments demonstrated that we are able to study the atmospheric fate of nitrogen oxides that has significant impact on global climate and hydrological cycle, thus affecting the likelihood of local floods and acid rain.