Las ramblas valencianas: algunos aspectos de hidrología, geomorfología y sedimentología

Two-Dimensional Hydraulic Modeling and Analysis of Morphological Changes in the Palancia River (Spain) During a Severe Flood Event on October 2000

This paper analyzes the possibilities that mathematical models offer to reconstruct flood events, and to predict their erosional and sedimentary effects. To that end, the severe flood event of October 2000 of the Palancia River (Valencia, Spain) is assessed. The hydraulic reconstruction was performed with the software GUAD 2D, a two-dimensional mathematical simulation model for shallow water conditions. The results obtained from the mathematical model and the hydraulic-sedimentological analysis were compared with the flood-related features mapped by means of geomorphologic photo-interpretation and field observations. This comparative study illustrates that these models constitute a powerful…

Procesos fluviales en lechos con materiales gruesos

Fluvíal processes ingravel-bed rívers. The bedload transport processes ingravel-bed rívers are not very known. The two most frequent features that characterize these rívers are the presence of a scour layer and the pavement. The coarse surface layer causes a great resistance to flow in gravel-bed rívers. So, flow resítance equations for computing average velocity can be applíed.

Flood events in Mediterranean ephemeral streams (ramblas) in Valencia region, Spain

This article deals with flood events in Mediterranean ephemeral streams typical of the Valencia region. The combination of the basin physical characteristics steep slopes, sparse vegetation, thin soils and permeable rock. and intense, heavy and irregularly distributed rain, generates flash floods. Runoff generation is sudden, giving rise to flash floods with sharp, narrow hydrographs with short time lags. The high amount of runoff is, nevertheless, only a small fraction of the total rainfall, since the characteristics of the river basins are such that infiltration of large amounts of water occurs. Using daily hydrological data from the Rambla de la Viuda basin and 5-min data from both the B…

Variabilidad espacial de los cambios de cauce en una rambla mediterránea en las seis últimas décadas (1946-2006)

An analysis of morphological changes during the last six decades is presented for the Rambla de Cervera, a Mediterranean ephemeral stream located in the eastern sector of the Iberian Mountain Range. The studied channel (16.5 km) has two contrasted sectors: a horst confined sector (5.5 km) and a graben sector (11 km). Channel changes were analysed through the analysis of aerial photographs, with geographical information systems (GIS) and comparison of topographic surveys made with a GPS-RTK. Between 1946 and 2006 the Rambla de Cervera, underwent channel adjustments comparable to those observed in other Mediterranean rivers. The gravel channel markedly narrowed, losing width (68.5%) and chann…

Las crecidas en ramblas valencianas mediterráneas

This paper takes into account the characterisation of ephemeral stream hydrology from Mediterranean environments. The heavy floods that these countries suffer are due to firstly, the physical watershed features (steep slopes, scarced vegetation cover and thin soils) and, secondly, to the intense and variable rainfall. Large quantities of precipitation fall in a matter of hours, or even minutes, over very steep catchments, causing catastrophic flash-floods, with very pointed hydrographs and short time lags. Using hydrological daily data from the Rambla de la Viuda basin and five-minute data from both Barranc de Carraixet and Rambla de Poyo basins, we have analysed the rainfall- runoff proces…

Evolución urbana e inundaciones en Castelló

La ciudad de Castellón está sometida a un elevado riesgo de inundación, derivado de su localización en el abanico aluvial del Riu Sec de Borriol. La interpretación en clave geomorfológica de las noticias históricas y actuales ha permitido reconstruir los procesos de desbordamiento de los cauces funcionales (Riu Sec, Barranc del Sol y de Penya-Roja) y de los paleocauces (Barranc de Fraga, la Sequiota, paleocauces del Riu Sec), así como las dimensiones y ubicación de las zonas inundables. Así pues, la movilidad de los cauces a escala geológica y/o histórica explica la dinámica de las inundaciones actuales, aunque el crecimiento urbano y las diferentes obras hidráulicas practicadas en los cauc…

Channel forms and vegetation adjustment to damming in a Mediterranean gravel‐bed river (Serpis River, Spain)

Assessment of channel changes in a Mediterranean ephemeral stream since the early twentieth century. The Rambla de Cervera, eastern Spain

An analysis of morphological changes during the last six decades is presented for a 16.5-km reach of the Rambla de Cervera, a Mediterranean ephemeral stream located in eastern Spain. Channel changes were analysed through a range of techniques, specifically the analysis of aerial photographs with geographical information systems (GIS) and comparison of topographic surveys. The gravel channel underwent a general decline over the study period, losing width (68.5%) and surface area (45.7%). Incision ocurred along the entire study reach at an average depth of 3.5 m. Natural and human-induced factors producing contradictory effects are considered responsible for changes in the Rambla de Cervera

Las inundaciones de la Plana de Castelló

La llanura costera comprendida entre Benicàssim y Borriana, conformada por numerosos abanicos aluviales ¿entre los que se asientan marjales en fase de colmatación¿ resulta anegada por las aguas de forma recurrente. En la zona de estudio se identifica una variada tipología de inundaciones dependiendo de la morfología del terreno y de la acción antrópica. La desaparición de los barrancos ¿sector al norte del Millars¿, las secciones insuficientes ¿Riu Sec de Borriol¿, la ocupación de cauces y paleocauces ¿al sur del Millars¿ y la propia configuración de las marjales, son los factores que determinan los procesos de inundación. La interferencia entre los factores naturales y la intervención antr…

Flood processes and morphological changes in aggradational ephemeral rivers. Reconstruction of the October 1957 flood in the Rambla Castellarda (Spain)

During the latter half of the twentieth century, Mediterranean ephemeral rivers underwent a profound metamorphosis. Fluvial adjustment processes narrowed the channels, simplified their planform pattern and notably reduced sediment availability. Today, this makes it extremely difficult to analyse the behaviour of this type of river in former aggradational contexts, such as those seen at the middle part of the twentieth century. For this reason, this paper addresses a reconstruction and analysis of the 1957 flood that occurred in the Rambla Castellarda, a tributary of the Turia river. The research is based, among other sources, on a series of extraordinary, high-precision aerial photographs c…

La geomorfología y las inundaciones en al plana de Vinarós-Benicarló

En este artículo se estudia la dinámica de las inundaciones en la plana de Vinaròs- Benicarló. El reconocimiento de las principales formas aluviales, las noticias de las crónicas históricas, los aforos y el análisis de la acción antrópica, permiten establecer dos sectores diferenciados. En la mitad septentrional de la plana, los problemas se derivan de la gran cantidad de cauces y paleocauces formados sobre los abanicos aluviales del Riu de la Sénia, del Cervol y de la rambla de Cervera, que conducen las aguas hacia los núcleos de población. Los puntos de desbordamiento de los cauces son los puentes y las rupturas de pendiente del canal. En el sector meridional las aguas se concentran en do…

Channel forms recovery in an ephemeral river after gravel mining (Palancia River, Eastern Spain)

[EN] During the 1970s, the Palancia River was intensively affected by gravel mining instream. This activity completely destroyed the fluvial forms, devastating the original wandering pattern. At the end of the 1980s, gravel mining ceased and the river started a process of recovery, only altered by several clearing operations. The aim of this work is to describe these processes of change, analyzing the river's morphosedimentary conditions through a GIS analysis of aerial photographs previous to, simultaneous with, and subsequent to the intense gravel mining activity. Results explain the current difficulties of some ephemeral rivers to recover their original forms, because of the sediment and…

Mediterranean Coastal Lagoons

On the eastern coast of the Iberian Peninsula—between the Ebro Delta and Cape Palos—the conditions during the Pleistocene, and especially after the Flandrian transgression, favoured the development of beach barrier systems and lagoons along large segments of the coast. The very small tidal range made connections between the sea and lagoons difficult, and this favoured sedimentation processes, which was often accelerated by human activity. Three very different sectors have been differentiated: the Gulf of Valencia, where the largest number of lagoons is found; the cliffed Betic structural sector between Cape Sant Antoni and Cape de les Hortes, in which there are just a few very small lagoons…