Evaluation of a grid-based river flow model using regional climate model output over Europe

Regional Climate Models (RCMs) offer significant improvements over Global Cli- mate Models in terms of their representation of rainfall at the spatial and temporal scales required for hydrological modelling. Here we test a new implementation of a grid-based hydrological model embedded in a model of land-surface climatology (the Joint UK Land Exchange Scheme; JULES) against observed river flows in sev- eral major NW European rivers, including the Rhine, Maas, Elbe, Danube, Loire, and Seine. Our hydrological model includes a probability-distributed model of soil mois- ture and runoff production (PDM) coupled with a discrete approximation to the one- dimensional kinematic wave equation to route surface and subsurface water downs- lope (G2G). The model was driven with hourly output from the Hadley Centre regional climate model, using results from the ERA-40 reanalysis experiment as boundary con- ditions (1961-2000). The results of simulations for river catchments in northwest Eu- rope are presented and compared with measured river flows over the same time period, for the same locations. The success with which the runoff production and flow routing components of the land-surface model match observed flow data is evaluated

Framework for setting up a Hydro-JULES perturbed parameter ensemble (PPE)

Land surface and hydrological processes and feedbacks that act at sub-grid scales need to be parameterised within models. These parameterisation schemes are an important source of uncertainty in model simulations. One of the aims of Hydro- JULES (HJ) is to quantify uncertainties in river flows induced by land surface and hydrological model parameterisations

Quantifying the geomorphic effect of floods using satellite observations of river mobility

Geomorphologists have long debated the relative importance of disturbance magnitude, duration, and frequency in shaping landscapes. For river-channel adjustment by floods, some argue that the cumulative hydrograph, rather than magnitude or duration, matters most. However, studies of flood-induced river-channel change often draw upon small data sets. Here, we combine Sentinel-2 imagery with flow data from laterally active rivers to address this question using a larger data set. We apply automated algorithms in Google Earth Engine to map rivers and detect their lateral shifting; we generate a large data set to quantify planform erosion during 175 floods at 34 selected sites. Erosion during these floods is best explained by their duration and then their cumulative hydrograph. We use a random forest regression model to predict flood-induced erosion, with potential applications for hazard management. Ultimately, better global data on sediment supply and caliber would help us to understand flood-driven change to river planforms

The current state of the use of large wood in river restoration and management

Trees fall naturally into rivers generating flow heterogeneity, inducing geomorphological features, and creating habitats for biota. Wood is increasingly used in restoration projects and the potential of wood acting as leaky barriers to deliver natural flood management by “slowing the flow” is recognised. However, wood in rivers can pose a risk to infrastructure and locally increase flood hazards. The aim of this paper is to provide an up-to-date summary of the benefits and risks associated with using wood to promote geomorphological processes to restore and manage rivers. This summary was developed through a workshop that brought together academics, river managers, restoration practitioners and consultants in the UK to share science and best-practice on wood in rivers. A consensus was developed on four key issues: (i) hydro-geomorphological effects, (ii) current use in restoration and management, (iii) uncertainties and risks, and (iv) tools and guidance required to inform process-based restoration and management

Evaluation of a grid-based river flow model configured for use in a regional climate model

Regional Climate Models (RCMs) offer significant improvements over Global Climate Models in terms of their representation of rainfall at the spatial and temporal scales required for hydrological modelling. To take advantage of these improvements, we test a new implementation of a grid-based hydrological routing model coupled with a model of land-surface climatology (the Joint UK Land Exchange Scheme; JULES) against observed river flows in several major European rivers, including the Rhine, Maas, Elbe, Danube, Loire, and Seine. Our model comprises a gridded land-surface model with a probability-distributed model of soil moisture and runoff production coupled with a discrete approximation to the one-dimensional kinematic wave equation to route surface and subsurface water from cell to cell in order to estimate river flow. The model was driven with hourly output from the Hadley Centre regional climate model, HadRM3P, run over the same grid, which in turn was driven using quasi-observed boundary conditions derived from the ERA-40 reanalysis experiment for the period 1961–2002. Observed 3-h precipitation data for the period 1999–2002 were also used as model forcing to provide a clearer indication of the hydrological model performance. The results from simulations for the six rivers are presented and compared with measured river flows over the same time period. They demonstrate that the hydrological model is able to simulate flows in rivers at the resolution of the RCM with some accuracy and thus has significant potential to assess the implications of projected regional climate change on river flows

Seismically Induced Erosion and the Mass Balance of a Large Earthquake

Earthquakes create topographic relief by opposite displacements of the Earth's surface on either side of a fault. Over a seismic cycle most energy is released in large earthquakes, and they are thought to be the principal cause of relief formation in tectonically active areas. But the topographic effect of earthquakes is reduced by seismically induced erosion. Earthquakes trigger slope failure, often in proportion to their strength, and increase substrate erodibility through shattering of rock mass and coalescence of cracks. Intense mass wasting has been reported from the epicenters of many large earthquakes, and a link between earthquakes and increased fluvial sediment transport has been demonstrated. After an earthquake, enhanced erosion persists, and its intensity and decay determine the net topographic effect of the earthquake. We have calculated the mass balance and topographic effect of the MW7.6 Chi-Chi earthquake in west Taiwan. Rates of mass wasting in the Chi-Chi epicentral area increased fivefold due to the earthquake, and have decayed since then to background values. The sediment concentration in the epicentral Choshui River has closely tracked hillslope mass wasting, and from the excess sediment load of typhoon floods following the earthquake, we estimate that about half of the co- and post seismic surface elevation has been removed by seismically-induced erosion. Further erosion at background rates will annul the remaining earthquake topography faster than the return time of large earthquakes in this area. These findings have broad implications for the timing and magnitude of the erosional sediment flux from the Taiwan mountain belt and the mechanisms driving its orogenesis

Coping with the curse of freshwater variability: Institutions, infrastructure, and information for adaptation

Institutions, infrastructure, and information for adaptation</jats:p

Geomorphology and earth system science

Earth system science is an approach to obtain a scientific understanding of the entire Earth system on a global scale by describing how its component parts and their interactions have evolved, how they function, and how they may be expected to continue to evolve on all time-scales. The aim of this review is to introduce some key examples showing the role of earth surface processes, the traditional subject of geomorphology, within the interacting Earth system. The paper considers three examples of environmental systems in which geomorphology plays a key role: (i) links between topography, tectonics, and atmospheric circulation; (ii) links between geomorphic processes and biogeochemical cycles; and (iii) links between biological processes and the earth’s surface. Key research needs are discussed, including the requirement for better opportunities for interdisciplinary collaboration, clearer mathematical frameworks for earth system models, and more sophisticated interaction between natural and social scientists

Detection of slow‐moving landslides through automated monitoring of surface deformation using Sentinel‐2 satellite imagery

Landslides are one of the most damaging natural hazards and have killed tens of thousands of people around the world over the past decade. Slow-moving landslides, with surface velocities on the order of 10−2–102 m a−1, can damage buildings and infrastructure and be precursors to catastrophic collapses. However, due to their slow rates of deformation and at times subtle geomorphic signatures, they are often overlooked in local and large-scale hazard inventories. Here, we present a remote-sensing workflow to automatically map slow-moving landslides using feature tracking of freely and globally available optical satellite imagery. We evaluate this proof-of-concept workflow through three case studies from different environments: the extensively instrumented Slumgullion landslide in the United States, an unstable lateral moraine in Chilean Patagonia and a high-relief landscape in central Nepal. This workflow is able to delineate known landslides and identify previously unknown areas of hillslope deformation, which we consider as candidate slow-moving landslides. Improved mapping of the spatial distribution, character and surface displacement rates of slow-moving landslides will improve our understanding of their role in the multi-hazard chain and their sensitivity to climatic changes and can direct future detailed localised investigations into their dynamics