Hywel Griffiths

Remote sensing and GIS analysis for mapping spatio-temporal changes of erosion and deposition of two Mediterranean river deltas: The case of the Axios and Aliakmonas rivers, Greece

Abstract Wetlands are among Earths most dynamic, diverse and varied habitats as the balance between land and water surfaces provide shelter to a unique mixture of plant and animal species. This study explores the changes in two Mediterranean wetland delta environments formed by the Axios and Aliakmonas rivers located in Greece, over a 25-year period (1984–2009). Direct photo-interpretation of four Landsat TM images acquired during the study period was performed. Furthermore, a sophisticated, semi-automatic image classification method based on support vector machines (SVMs) was developed to streamline the mapping process. Deposition and erosion magnitudes at different temporal scales during the study period were quantified using both approaches based on coastline surface area changes. Analysis using both methods was conducted in a geographical information systems (GIS) environment. Direct photo-interpretation, which formed our reference dataset, showed noticeable changes in the coastline deltas of both study areas, with erosion occurring mostly in the earlier periods (1990–2003) in both river deltas followed by deposition in more recent years (2003–2009), but at different magnitudes. Spatial patterns of coastline changes predicted from the SVMs showed similar trends. In absolute terms SVMs predictions of sediment erosion and deposition in the studied area were different in the order of 5–20% in comparison to photo-interpretation, evidencing the potential capability of this method in coastline changes monitoring. One of the main contributions of our work lies to the use of the SVMs classifier in coastal mapping of changes, since to our knowledge use of this technique has been under-explored in this application domain. Furthermore, this study provides important contribution to the understanding of Mediterranean river delta dynamics and their behaviours, and corroborates the usefulness of EO technology and GIS as an effective tool in policy decision making and successful landscape management. The latter is of considerable scientific and practical value to the wider community of interested users, given the continued open access to observations from this satellite radiometer globally.

A sensitivity analysis of the SimSphere SVAT model in the context of EO-based operational products development

Use of simulation process models often combined with Earth Observation (EO) data, has played a key role in extending our abilities to study land surface interaction processes and enhancing our understanding of how different components of the Earth system interplay. Use of these synergistic techniques aims to improve the estimates of key parameters characterising land surface interactions by combining the horizontal coverage and spectral resolution of remote sensing data with the vertical coverage and fine temporal continuity of simulation process models.This study performs a Global Sensitivity Analysis (GSA) on the SimSphere land surface model aiming to further extend our understanding of the model structure and establish its coherence. It builds on previous works conducted on the model to which a sophisticated and cutting edge GSA meta-modelling method adopting Bayesian theory is implemented. Our first objective is to examine the effect of assuming uniform probability distribution function (PDFs) for the model inputs/outputs on the sensitivity of key quantities simulated by SimSphere. A further objective is to explore the sensitivity of new, previously unexplored variables simulated by the model, namely of the Daily Evaporative, Non-Evaporative Fractions and Radiometric Temperature.The GSA conducted assuming uniform PDFs showed comparable results to previous studies in terms of identifying the most sensitive model inputs to each of the outputs considered. Yet, in absolute terms, the statistical parameters measuring the sensitivity of the model inputs were notably different. SA on the newly examined model outputs showed largely explainable results and allowed identification of the most responsive model inputs and interactions. In general, our results provided further evidence supporting the model coherence and correspondence to the behaviour of a natural system. The implications of the main findings are discussed in the framework of the model use either as a stand-alone tool or synergistically with EO data, particularly so towards the operational development of such products. Assumption of different PDFs for model inputs/outputs has no major bearing on the SA results to the selected variables simulated by the model.Our results further extend our understanding of the structure and capability of SimSphere, the use of which is currently expanding worldwide.Results can be of key practical value in developing global operational products from EO data in methods using SimSphere.

Operational evapotranspiration estimates from SEVIRI in support of sustainable water management

This study aimed at evaluating the accuracy of the evapotranspiration (ET) operational estimates from the Meteosat Second Generation (MSG) Spinning Enhanced Visible Infra-Red Imager (SEVIRI) at a range of selected ecosystems in Europe. For this purpose in-situ eddy covariance measurements were used, acquired from 7 selected experimental sites belonging to the CarboEurope ground observational network over 2 full years of observations (2010–2011). Appraisal of ET accuracy was also investigated with respect to land cover, season and each site(s) degree of heterogeneity, the latter being expressed by the fractional vegetation cover (FVC) operational product of SEVIRI. Results indicated a close agreement between the operational product’s ET estimates and the tower based in-situ ET measurements for all days of comparison, showing a satisfactory correlation (r of 0.709) with accuracies often comparable to previous analogous studies. For all land cover types, the grassland and cropland sites exhibited the closest agreement (r from 0.705 to 0.759). In terms of seasons the strongest correlations were observed during the summer and autumn (r of 0.714 & 0.685 respectively), and with FVC the highest correlation of 0.735 was observed for the class FVC 0.75-1 when compared against the observed values for the complete monitoring period. Our findings support the potential value of the SEVIRI ET product for regional to mesoscale studies and corroborate its credibility for usage in many practical applications. The latter is of particular importance for water limiting environments, such as those found in the Mediterranean basin, as accurate information on ET rates can provide tremendous support in sustainable water resource management as well as policy and decision making in those areas.

Sensitivity Exploration of SimSphere Land Surface Model Towards Its Use for Operational Products Development from Earth Observation Data

The use of Earth Observation (EO) data combined with land surface process models is at present being explored to assist in better understanding the natural processes of the Earth as well as how the different components of the Earth system interplay. However, before applying any modelling approach in performing any kind of analysis or operation, a variety of validatory tests needs to be executed to evaluate the adequacy of the developed “model” in terms of its ability to reproduce the desired mechanisms with the necessary reality. Sensitivity analysis (SA) is an integral and important validatory check of a computer simulation model or modelling approach before it is used in performing any kind of analysis operation. The present study builds on previous works conducted by the authors in which a sophisticated, cutting edge SA method adopting Bayesian theory has been implemented on a land surface process model called SimSphere with the aim of further extending our understanding of its structure and of establishing its coherence. This land surface model has been widely used as an educational tool in different Universities across the world, as a stand-alone tool and synergistically with EO data in deriving key parameters characterising land surface processes. SimSphere use is currently under investigation by two Space Agencies for deriving spatio-temporal estimates of energy fluxes and soil surface moisture from a technique in which the model is used synergistically with Earth Observation data. The GSA method employed here provided a further insight into the model’s architectural structure, and allowed us to determine which model input parameters and parameter interactions exert a significant influence on the selected model outputs, and which are inconsequential. Analysis of the SA results indicated that only a small fraction of the model input parameters have an appreciable influence on the examined target quantities. Results, however, did suggest the presence of highly complex interactions structure within SimSphere, which drove a considerable fraction of the variance of the variables simulated by the model. The main findings are discussed in the context of the future model use including its synergy with EO data for deriving the operational development of key land surface parameters from space.

Water under the bridge? Nature, memory and hydropolitics:

Memories are not confined to those who experience them firsthand. Rather, they can be transmitted and repeated by subsequent generations as prosthetic and moral memories, not linked solely to specific geographic locations but extending to affect and inform contemporary political debates. This paper investigates how and why the 1965 flooding of the village of Capel Celyn in the Tryweryn valley, north Wales is remembered through textual analysis of Welsh literature and popular music. It also highlights the profound impact that struggles over resources can have on social, cultural and political landscapes. The flooding, arguably the most dramatic hydropolitical event in the history of the United Kingdom, created tension between the need to protect cultural identity on the one hand and on the other, the need to provide essential natural resources for industry and urban development. The memory of this event has been sustained in Wales in a number of ways. Visually, graffiti calling on the public to ‘remember Tryweryn’ has become a tangible symbol of Welsh nationalism, and a potent part of the Welsh landscape. In Welsh literature (poems and songs) the memory of Tryweryn has been expressed in terms of loss and shame and the defilement of nature. Politically, Tryweryn provided the context for the rise of Welsh nationalism and devolution and has become a regularly used symbol of a culture under threat. Crucially, the memories now influence and inform contemporary debates around precipitation, drought and any forced removal justified in the name of progress.

Acknowledging the work of poetry: a collaborative commentary on Tim Cresswell’s FenceFence. By CresswellTim. London: Penned in the Margins. 2015. 72 pp. £9.99 paperback. ISBN: 9781908058317.

For the philosopher Stanley Cavell,1 literature begins where traditional philosophy ends. In his most famous work The Claim of Reason he asks whether it is possible for philosophy to acknowledge that which it cannot know: can philosophy come to be faithful to the unknowable rather than consistently trying to transcend it? Cavell finds salvation in literature because it approaches the esoteric and the mysterious not as things to think ourselves out of but as things to contend with. It approaches unknowabilities as unknowabilities and marks their mystery as the object of investigation. I am reminded of Cavell whenever I am faced with the ever-increasing emergence of creative work in geography. Here, I am not referring to geographers being creative in their academic practice or to writers being self-consciously geographical. Both of these phenomena have been happening for some time. Rather, I am thinking of geographers becoming novelists, painters and poets2 and geographers who have explicitly left academic practice behind (or at least set it aside) to explore geography through a different literary convention. The relevance of Cavell’s question applies equally to geography as it does to philosophy. What does creativity do for geography? Where does the literary take geography? Does the geographical novel contend with the mystery of space and time? Does the landscape painting engage with the ineffability of perspective and vision? Does the poem struggle with the esoteric centre of place and home? What does creative work allow that traditional academic practice does not? What does it open that academic practice keeps closed? While geographers are often willing to speak volumes about why they engage in academic work, they are more hesitant when it comes to their more creative ventures. ‘I recently decided to 732982 CGJ0010.1177/1474474017732982cultural geographiesbook review essay book-review2017

Incorporating sedimentological data in UK flood frequency estimation

This study presents a new analytical framework for combining historical flood data derived from sedimentological records with instrumental river flow data to increase the reliability of flood risk assessments. Historical flood records were established for two catchments through re-analysis of sedimentological records; the Nant Cwm-du, a small, steep upland catchment in the Cambrian Mountains of Wales, and a piedmont reach of the River Severn in mid Wales. The proposed framework is based on maximum likelihood and least-square estimation methods in combination with a Generalised Logistic distribution; this enables the sedimentological data to be combined effectively with existing instrumental river flow data. The results from this study are compared to results obtained using existing industry standard methods based solely on instrumental data. The comparison shows that inclusion of sedimentological data can have an important impact on flood risk estimates, and that the methods are sensitive to assumptions made in the conversion of the sedimentological records into flood flow data. As current industry standard methods for flood risk analysis are known to be highly uncertain, the ability to include additional evidence of past flood events derived from sedimentological records as demonstrated in this study can have a significant impact on flood risk assessments.

Three poems on flood histories in rural Ireland

This article presents three poems inspired by archival research on historical perceptions of flooding and river engineering in Galway city and its rural hinterland. Relationships between people and water, as recorded in early-20th-century minutes of a vice-regal commission on river drainage in rural Ireland and historical newspaper accounts of flooding, are explored and reimagined. The poems focus particularly on the management of flood risk and geomorphological processes (erosion and sedimentation), ‘arterial drainage,’ and individual emotional responses to traumatic floods and their impacts. Reflecting on these poems, I suggest that part of poetry’s contribution to the discipline is to provide a new and exciting way of engaging with the archive.

Searching for an Anthropo(s)cene in the Uplands of Mid Wales

This essay presents the responses of four creative writers to the highly modified landscapes of the Cambrian Mountains in mid Wales. Through a tour of the historic mine site of Cwmystwyth and the dams of Cwm Elan, our aims were to engage with the concept of the Anthropocene in a landscape that could be emblematic of the proposed new geological interval. Through poems and prose inspired by these landscapes, the physical, social, cultural, and political processes shaping them are explored. The pieces have a strong sense of place, and touch on themes of pollution of the environment by heavy metals, geomorphological impacts of dams, and the human stories associated with those places. We demonstrate the great potential of such places and landscapes as sites where artistic creativity and science can engage and collaborate to find ways of communicating concepts such as the Anthropocene and the anthroposcenic.

Chapter 5 – Spatiotemporal Estimates of Surface Soil Moisture from Space Using the Ts/VI Feature Space

Abstract Earth Observation (EO) has played an imperative role in extending our abilities for obtaining information on the spatio-temporal distribution of surface soil moisture (SSM). A wide range of techniques have been proposed for this purpose. Some of those techniques have based on the integration of satellite-derived estimates of Fractional Vegetation Cover (Fr) and Land Surface Temperature (Ts) in the form of a scatterplot domain, often combining land surface process model simulations. These techniques aim at combining the horizontal coverage and spectral resolution of EO imagery with the vertical coverage and fine temporal continuity of the process models. Herein one such technique - named the “triangle” - has been implemented with EO datasets from both the AATSR and ASTER sensors together with SimSphere land surface model. Validation of the derived SMC maps was undertaken in different sites in Europe representing a variety of climatic, topographic and environmental conditions, for which validated in-situ observations from diverse operational ground observational networks were available. Results indicated a good agreement between the in-situ and both “triangle” schemes for the estimation of SMC (ASTER R – 0.561/AATSR R – 0.844), with the AATSR results again outperforming the ASTER, comparable to previous studies implemented using different types of EO data. Comparisons of the derived SMC maps regionally against other satellite-derived products also showed largely an explainable distribution of SMC in relation to surface heterogeneity. Our results provide strong supportive evidence for the potential value of the “triangle” inversion modelling technique to accurately derive estimates of SMC, and are important steps as well towards efforts focusing on operational implementation of this approach.