Project

RIVERCHANGES: Recent Changes in Cantabrian rivers: Analysis, causality and prospective

Goal: During the last decades, Cantabrian rivers have experienced riverbed's incision, channel narrowing, vegetal colonization, loss of active gravels and abandonment of secondary channels. These changes have been usually related to a general decrease in sediment supply after land-use changes. We analyze: a) long-term geomorphological changes in the channel, b) short-term changes in the sediment movement using sequential Digital Surface Model (Drone flights) and seismograph monitoring, c) statistical analysis of rainfall and discharge trends. We explore their links to afforestation/land abandonment, flood hazards and habitat and biodiversity loss.

Methods: Geomorphological Mapping, Hydrological Modeling, Statistical Algorithms, Sediment Transport, Seismic Interpretation

Date: 1 January 2016 - 1 June 2019

Updates
0 new
0
Recommendations
0 new
0
Followers
0 new
14
Reads
0 new
75

Project log

Elena Fernandez Iglesias
added a research item
Fluvial systems draining the northern watershed of Cantabrian mountains (NW Spain) are characterized by short paths and steep slopes. During the last decades, the morphology of the river channel has experienced several changes: riverbed's incision, channel narrowing, vegetal colonization, loss of active gravels and abandonment of secondary channels. Similar trends were described in other rivers from Spain and European mountains. Several studies related this trend with a general decrease in sediment supply due to land-use changes happened in the second half of the century XX, most of related to afforestation and land abandonment. The preliminary results in the Saja river basin support this hypothesis because of a decreasing around 40 % in the active channel surface has happened during the last 60 years, most of them from 1956 until 1989. This trend is well correlated to the main changes in the shrub and tree vegetation.
Elena Fernandez Iglesias
added a research item
Seismic data are typically employed to monitor earthquake activity, but they can also be exploited in order to investigate the existing links betweenthe seismic signal and a broad range of physical processes occurring in the nearby rivers. For instance, the noise related to water turbulence duringhigh discharges has a clear impact on the seismic signal. Concurrently, high-flows in gravel-bed rivers involve the displacement of large volumesof coarse sediment particles, travelling as bedload, which in turn should be the source of an additional and non-negligible amount of seismic noise.Data derived from the 3-years seismic monitoring of a gravel-bed river located in NW of Spain are considered. First, we have accomplished spectralanalysis over the seismic noise generated by more than 10 river flow events with high discharge. Then, we have applied several statistical analysisnot only for calibrating the functions describing the links between seismic noise and fluvial discharge but also in order to identify the thresholds fordetection of incipient bedload transport and geomorphic change in the seismic signal.
Daniel Vázquez Tarrío
added a research item
Streambed mobility in gravel-bed rivers is largely controlled by the rate at which particles with different grain sizes are recruited from the riverbed into the bed load. In this paper, we present a study case in which we explored this question, based on combining field observations using painted plots and the grain size analysis of a large flood sediment deposit in the River Esva, northwest Spain, and the generalized threshold model (GTM) competence model developed by Recking. The main aim was to accomplish a complete characterization of streambed mobility in this river. The obtained results suggest the large potential of the GTM model compared to previous competence models when searching for the quantitative description of particle entrainment and streambed mobility in the River Esva. We observed how the grain size of the bed load in the River Esva tended to be closer to that of the sub-armour bed material during large floods, while moderate magnitude flows tended to carry a relatively fine bed load. Additionally, we compared our results with previously published field observations on flow competence. This comparison outlined the large degree of site specificity in the links between grain size of the bed load and that of the bed material.
Elena Fernandez Iglesias
added 2 research items
The river channel in the Esva basin, a coastal catchment of the Cantabrian region (Northwest of Spain), has experienced a slight active channelwidth decrease from 1957 to 1985 (<1%) and more important decrease (close to 13%) from 1985 to 2003. This trend is well related to the main changes in the forest cover, which also increases slightly from 1957 to 1985 and more importantly after 1985 until now. Models for different scenarios were applied for the daily datasets before and after 1985 with the aim of identifying whether the changes in the land uses might influence in the hydrological response of the river to the rainfall. The preliminary results focused on flow peak events conclude a light increase in this time reaction rainfall-flow in agreement with the land usage changes.
The aim is to analyze time series representing daily rainfall events collected in the Esva river basin in Asturias (northwest of Spain) during the last 50 years, where there is a lack of quantitative data about climatic oscillations. Our interest is a better understanding of the seasonal patterns found in these data and of possible trends which might indicate effects of climate change. An exploratory data analysis leads us to a first order Markov model with alternation between wet and dry periods. The probability of rainfall is modeled by logistic regression, and precipitation values on wet days are described by Gamma distributions with a first order autoregressive dependence structure. Lowess smoothing is used to include seasonality in both submodels because the seasonal pattern could not be covered adequately by standard periodic functions. A tentative result of our analysis is some evidence that dry periods get longer in the course of time, while precipitation values on wet days might be unaffected.
Arturo Colina
added a research item
Fluvial systems draining the northern watershed of Cantabrian mountains (NW Spain) to the Bay of Biscay are characterized by single-thread channels with short paths and steep slopes. During the last decades, they have experienced riverbed's incision, channel narrowing, vegetal colonization, loss of active gravels and abandonment of secondary channel s. Similar trends have been described in other rivers from Spain and temperate Europe, and they ha ve been usually related to a general decrease in sediment supply after land-use changes. Here we pre sent the preliminary results of a research project aiming at analyzing these long-term geomorphologica l and hydrological trends in Cantabrian rivers, and exploring their links to afforestation and land abandonment.
Elena Fernandez Iglesias
added 2 research items
The river channel in the Esva basin, a coastal catchment of the Cantabrian region (North Iberian Peninsula) with a surface of 464 km2 and maximum high close to 1300 m, has experienced riverbed’s incision, channel narrowing, vegetal colonization and loss of active gravels. This trend has been described in other rivers from Spain and Europe, and they could been linked to a general decrease in sediment supply after land-use changes and/or hydrological changes in rainfall and fluvial discharge. In the latter case, a statistical analysis of the relation between rainfall and fluvial discharge since 1970 is carried out. The impact of the recorded precipitations on the fluvial discharge is analysed based on lagged dependent variable models for different scenarios, trying to detect if there are important hydrological changes.
During the last decades, fluvial systems of the Cantabrian region (Northwest of Spain) have experienced important geomorphological changes. These changes are characterized by main channel incision and narrowing, vegetal colonization of fluvial bars and channel morphology simplification. This trend has been described in other spanish and Atlantic European rivers. Some authors suggest that these changes are caused by a general decrease in sediment supply rates. Current data available for Cantabrian basins are consistent with this interpretation, but no systematic analysis has been carried out yet to support this hypothesis. In this context, evidences of this decrease in the sediment supply could find in the extent variations of coastal beaches and dunes, which are built mainly with the sand that comes from the rivers. Databases about waves height, fluvial flows and changes in the extension of dunes in the West coast of Asturias have been analyzed by fitting different regression models using R to identify trends in the sediment supply from the rivers and to discuss the influence of other marine variables, taking in account the potential impact of the dams and sea level changes related with the climatic change.
Arturo Colina
added a research item
Los ríos que fluyen por las cuencas septentrionales de la Cordillera Cantábrica (noroeste de España), caracterizados por cortos recorridos y elevados gradientes de pendiente, han experimentado durante los últimos años cambios en su morfología. Al igual que otras regiones montañosas de España y Europa, la tendencia observada es hacia la incisión vertical del lecho del río, el estrechamiento del canal, la colonización vegetal de barras activas y el abandono de los canales secundarios. Algunos estudios previos relacionan este tipo de cambios con una disminución de los aportes de sedimentos al sistema fluvial, provocado por los cambios en los usos del suelo acaecidos durante la segunda mitad del siglo XX, principalmente aquellos asociados a la forestación de terrenos y al abandono progresivo de las prácticas agrarias tradicionales. Los resultados preliminares obtenidos en la cuenca del río Saja confirman esta hipótesis, evidenciando en los últimos 60 años una disminución de la superficie del canal activo de en torno al 40 %, produciéndose la mayor parte del cambio en el periodo 1956-1989. Estos cambios presentan una buena correlación con la expansión detectada en la vegetación de porte arbustivo y arbóreo.
Elena Fernandez Iglesias
added 8 project references
Elena Fernandez Iglesias
added a project goal
During the last decades, Cantabrian rivers have experienced riverbed's incision, channel narrowing, vegetal colonization, loss of active gravels and abandonment of secondary channels. These changes have been usually related to a general decrease in sediment supply after land-use changes. We analyze: a) long-term geomorphological changes in the channel, b) short-term changes in the sediment movement using sequential Digital Surface Model (Drone flights) and seismograph monitoring, c) statistical analysis of rainfall and discharge trends. We explore their links to afforestation/land abandonment, flood hazards and habitat and biodiversity loss.