There is substantial evidence that land use/management changes (LUMCs) can impact runoff generation at the local scale; however, it is unclear how these impacts are modified as they travel through the river channel network to affect downstream catchment flooding. There is a need for data from multiscale monitoring studies in catchments undergoing known LUMCs to assess the extent to which impacts can be detected at increasing catchment scales. This understanding is needed in developing reliable methods for assessing the potential of rural based flood prevention and mitigation measures, urgently required by catchment planners. The aim of the present study is to generate and analyse a new multiscale dataset which will serve to gain a better understanding of the effects of local LUMCs on catchment response at increasing scales. This study investigates the impacts of recent LUMCs (drain blocking, stocking density changes, and afforestation) in the headwaters of the River Hodder (261 km²), North-West England, UK. An unusually dense nested monitoring network (28 stream gauges) was set up at scales ranging rom ~1 ha to 261 km². Data Based Mechanistic (DBM) modelling and a simple Storage Discharge Detection (SDD) model were used to compare pre- and post-change hydrographs at increasing scales in an effort to detect short-term change signals and their propagation to larger scales. A novel physically based Model for Upland Runoff Storage and Flow Fields (MURSAFF) was developed to further investigate the short- and long-term impacts of LUMC in complex landscapes at the micro catchment scale (~1 km²). The results were integrated into a semi-distributed catchment impact routing model to explore the effects on the downstream catchment response. No statistically significant evidence was found in the DBM and SDD results to suggest that any of the LUMCs had a short-term impact on catchment response at scales from 1 km² up to the Hodder catchment scale (261 km²). This is attributed to the proportion of area affected by change, the timescale of impacts, and the natural variability in catchment response. Short-term small scale (< 1 km²) field observations and MURSAFF predictions of the impacts of drain blocking involved an increase in the local storage and change in the flow fields. However, these changes are insignificant at the micro catchment scale. The MURSAFF simulated impacts of reductions in stocking density involve attenuation of the flood hydrograph mainly. Predictions of the downstream effects suggest they will be relatively small and different for each storm, with the lack of internal synchronisation of the sub-catchment responses and the natural variability therein being dominant factors in determining the impacts on the catchment outlet response. These predictions are consistent with the failure to detect any significant impacts in the post-change records.

No description available.

Recent large flooding events have reinforced the need for prudent flood risk management. The July 2007 floods in Yorkshire and the Midlands and the November 2009 floods in the Lake District have highlighted the current vulnerability of key infrastructure and the built environment in the UK to flooding. This existing flood risk is coupled with concerns over the potential impacts of future climate change on flood regimes. Therefore, there is a need to develop tools and methodologies to assess the potential impact of likely climate change on flood risk. The link between large rainfall and flow events is first examined, as well as an assessment of the seasonality of these events. This reveals a distinct east-west split in the seasonal concentration of flooding. This work provides a basis for the development of a statistical modelling technique which estimates a catchment flood record on an event basis. The model uses estimates of the flood generating storm and the antecedent conditions to estimate a flow magnitude. The modelled flood record is then transformed into a flood frequency curve using an appropriate statistical method. Extensive testing of the model has assessed its robustness to the length of flood record used in fitting and its sensitivity to the input climate data. Several case studies using the UKCP weather generator show how the method works as well as providing an indication of how future climate changes may affect the flood frequency curve. The frequency curve mapping method developed here performs best on catchments whose flood regime is driven by rainfall. The use of a simple antecedent rainfall accounting method has been shown to perform as well as a quasi-physical soil moisture estimation method. The research undertaken offers several possibilities to develop understanding of flood frequency curves in catchments with short gauged records. This new methodology has the potential for further development and can be used to explore a wide range of future scenarios.

Concern has arisen as to whether the lack of appropriate consideration to surface water in urban spatial planning is reducing our capacity to manage surface water flood risk. Appropriate tools are required that allow spatial planners to explore opportunities and solutions for surface water flooding at large spatial scales. An urban surface water balance model has been developed that screens large urban areas to identify flooded areas and which allows solutions to be explored. The model hypothesis is that key hydrological characteristics; storage volume and location, flow paths and surface water generation capture the key processes responsible for surface water flooding. The model uses a LiDAR DEM (Light Detection and Ranging Digital Elevation Model) as the basis for determining surface water accumulation in a catchment and has been developed so that it requires minimal inputs and computational resources. The urban surface water balance approach is applied to Keighley in West Yorkshire where several instances of surface water flooding have been reported. Data for validating surface water flood risk models is sparse because such flooding events are of short duration, very localized and distributed across the catchment. This research used a postal questionnaire, followed up with site visits to collect data on surface water flooding locations in Keighley. The validation exercise confirmed that the major processes responsible for flooding are largely well represented in the model for situations where interaction with the urban sewer network is well represented by the assumptions made in the model. A qualitative analysis based on field visits revealed that the degree of interaction with the sewer network varies spatially, and as the importance of the interaction of the sewer system increases, the accuracy of the model results are lowered. It also highlighted that local detail not present in the DEM, the presence of urban drainage assets and the performance of the sewer system, which are not be represented in the model, can determine the accuracy of model results. Model results were used as a basis to develop solutions to surface water flooding. A least cost path methodology was developed to identify managed flood routes as a solution. These were translated into model inputs in the form a modified DEM. It was shown that the simple and fast representation of flood routes and surface storage is of considerable benefit for scenario analysis.

No description available.

The engineering of natural river channels alters their morphology and hydraulic regime. In many cases this can adversely affect the riverine environment as well as cause instability. Several methods designed to predict channel change at engineered sites were evaluated using a range of river engineering schemes across England and Wales, which encompassed conventional and environmentally sensitive schemes in both upland and lowland areas. The methods tested included critical tractive force and permissible velocity theory, Griffiths natural stability index, Brookes stream power index, shear stress analysis, regime theory, sediment transport equations and one dimensional mathematical models. Of these, the use of sediment transport equations linked to rating curves for individual cross-sections, based on frictional characteristics, most accurately predicted the morphological changes recorded along the engineered reaches of simple channels. Their performance on compound channels was impaired due to the poor understanding of the frictional effect of the flood berms. It is recommended that this method be adopted to assess the stability of engineering proposals at the design stage. The impact of engineering schemes on aquatic niacrophytes is also evaluated. Five physical factors were found to influence individual species, namely channel depth, flow area, surface sediment size, bank slope and flow velocity. Tables are presented which allow the prediction of the species assemblage likely to be associated with a given engineering design. It is also clear that species diversity is increased if a range of habitats are incorporated within an engineering scheme, as has occurred on many of the environmentally sensitive flood relief schemes. These approaches to river engineering also appear to enhance the diversity of species above that for the natural channel, whereas conventional methods show the opposite trend. Such methods are therefore to be recommended as options in the design and rehabilitation of flood relief schemes.

Many multipurpose reservoirs are situated in the low mountain range of Germany. Most of them are necessary for drinking water supply and flood protection as well. Other utilizations are recreation, water power and the downstream low water regulation during dry seasons. The operation rules of the reser-voirs have to be optimized to meet the different requirements of use. One tool within this framework is a management system for river basins including all reservoirs and their specific operation rules affecting the downstream reaches. As an optimization objective for instance the minimization of inundation risks can be defined. In this case the risk can be defined as hydraulic and hydrologic safety of the reservoir itself and the risk due to inundation and damaging in the downstream regions. Considering the European Water Framework Directive the ecological aspect of reservoir management is one more point in the optimization process. To es-tablish a pilot project the software TALSIM will be applied to river catchments in the ore mountains (Saxony).

Die Broschüre vermittelt anschaulich, was von Gemeinden, Grundeigentümern, Bewirtschaftern und anderen Betroffenen auf lokaler Ebene unternommen werden kann, um Schäden durch Hochwasser vorzubeugen. Diskutiert werden Maßnahmen wie Flächenentsiegelung, angepasste Landwirtschaft, der Ausbau von Rückhaltebecken oder verbesserte Teichnutzungen. Erfolgreiche Beispiele aus der Praxis runden die Handlungsempfehlungen ab.

Afin de protéger les littoraux maritimes des effets dévastateurs, les digues à talus maritimes sont le plus souvent utilisées. Les dysfonctionnements possibles de ce type d’ouvrage à talus sont la rupture de la carapace conduisant ensuite à la rupture d’ensemble de la structure et les franchissements dépassant le critère de sécurité. L’un des plus utilisé, le modèle semi-empirique de Van der Meer (1987), a été développé pour décrire les conditions de stabilité des digues en enrochements sous l’action de la houle. Ce modèle s’avère incapable de décrire précisément l’influence de la perméabilité réelle du noyau sur la stabilité de la carapace. D’autre, pour une digue, un accroissement du niveau du plan d’eau accompagné par des houles d’intensité accrue va conduire à des aléas de rupture et de franchissement bien supérieurs à ceux prévus lors de la conception de l’ouvrage. Pour le premier modèle physique étudié d’une digue en enrochement naturel, nous avons cherché une relation empirique entre le paramètre P utilisé dans le modèle de VdM et le coefficient de perméabilité Ks réel du milieu poreux constituant le noyau par les deux approches. Le deuxième modèle physique d’une digue en enrochement artificiel est d’étudier différentes solutions de renforcement de digues maritimes existantes vis-à-vis de la remontée du niveau des mers et océans due au changement climatique. Nous validons avec les modèles classiques de prédiction pour le scénario initial de niveau marin et proposons de modifications des formulations existantes pour des scénarios de surélévation du niveau moyen des points de vue du franchissement et de dommage / To protect the devastation on coastal maritime, the slope breakwater are mostly used. The possible malfunctions of this type of slope structure are the damage on armor layer leading to the rupture of the entire structure and the exceeding the safety criterion of overtopping discharge. One of the most used, the semi-empirical model of Van der Meer (1987), has been developed to describe the conditions of stability of armor breakwater under wave attack. This model is unable to accurately describe the influence of the real core’s permeability on the stability of the armor layer. Besides, for a sea dike, an increasing of water level accompanied by intensive swell will lead to the risks of more breakage and wave overtopping than those anticipated in the design of the structure. In the first physical model study of a rubble mound breakwater, we research the empirical relation between the parameter P used in the model VdM and real permeability Ks of porous medium constituting the core layer by two approaches. The second physical model of concrete breakwater is to study the different reinforcement solutions to strengthen the existing sea dikes which face to face the rise in the level of seas and oceans due to climate change. We validate the classical models of prediction for the initial scenario of sea level and propose the modifications of existing formulations in the scenarios of sea elevation from the points of view of damage and overtopping

Many multipurpose reservoirs are situated in the low mountain range of Germany. Most of them are necessary for drinking water supply and flood protection as well. Other utilizations are recreation, water power and the downstream low water regulation during dry seasons. The operation rules of the reser-voirs have to be optimized to meet the different requirements of use. One tool within this framework is a management system for river basins including all reservoirs and their specific operation rules affecting the downstream reaches. As an optimization objective for instance the minimization of inundation risks can be defined. In this case the risk can be defined as hydraulic and hydrologic safety of the reservoir itself and the risk due to inundation and damaging in the downstream regions. Considering the European Water Framework Directive the ecological aspect of reservoir management is one more point in the optimization process. To es-tablish a pilot project the software TALSIM will be applied to river catchments in the ore mountains (Saxony).