Magnitude of formative flows in stream potholes

Although it is generally recognized that geomorphic work is tied to bedrock channel reshaping, the importance of low vs. high flow stages that cause the most geomorphic impact remains unclear. The objective of the research is to study the concept of “formative flow” in bedrock channels and determine, through morphological studies, if those flows have any impact on sculpted features such as potholes and how this relationship relates to various inputs such as flow stages (magnitude and frequency), shear stress, and sediment size. Here, we studied the distribution of the main pothole typologies and tried to understand why potholes are found along bedrock river channels. Specifically, we examined stream potholes from three locations along the Spanish Central System: Alberche, Tietar, and Manzanares rivers. We conducted the research by taking precise geometric measurements, classifying potholes, analyzing flow magnitude and frequency, and using a two-dimensional (2D) hydrodynamic model to assess key variables in Manzanares river. This research demonstrated that bankfull depths completely cover all pothole typologies in all the analyzed sites but are not sufficient to achieve its formative flow depth (FFD). Using a detailed 2D hydrodynamic model in Manzanares river, we discovered that dimensions of cylindrical potholes are closely related to bankfull discharge and that this depth is connected to FFD. Other potholes, such as erosive-compound and erosive-lateral, are historical remnants, and their shapes are not related to any particular FFD and are likely associated with rare events and catastrophic breaks. A collection of laterals that exhibit FFD near bankfull flows appear to represent a part of the recent evolution of a knickpoint. To summarize, it can be inferred from the findings that the utility of morphological analysis in conjunction with the 2D hydrodynamic model is to examine the fraction of erosional/active features to determine the degree of senescence and/or change in natural conditions in a river reach.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUERegional Government of Madrid (Spain)pu

Towards an increase of flash flood geomorphic effects due to gravel mining and ground subsidence in Nogalte stream (Murcia, SE Spain)

Transition from endorheic alluvial fan environments to well-channelized fluvial systems in natural conditions may occur in response to base-level fluctuations. However, human-induced changes in semi-arid regions can also be responsible for similar unforeseen modifications. Our results confirm that in-channel gravel mining and aquifer overexploitation over the last 50 years in the case study area have changed the natural stability of the Nogalte stream and, as a result, its geomorphic parameters including channel depth and longitudinal profile have begun to adapt to the new situation. Using interferometric synthetic aperture radar (InSAR) data we obtain maximum values for ground subsidence in the Upper Guadalentín Basin of  ∼ 10 cm yr−1 for the period 2003–2010. In this context of a lowered base level, the river is changing its natural flood model to a more powerful one. A comparison of the 1973 flood event, the most dramatic flood event ever recorded in the area, with the 2012 event, where there was a similar discharge but a sediment load deficit, reveals greater changes and a new flooding pattern and extension. In-channel gravel mining may be responsible for significant local changes in channel incision and profile. This, together with the collateral effects of aquifer overexploitation, can favour increased river velocity and stream power, which intensify the consequences of the flooding. The results obtained here clearly demonstrate an existing transition from the former alluvial pattern to a confined fluvial trend, which may become more pronounced in the future due to the time lag between the drop in aquifer level and ground subsidence, and introduce a new scenario to be taken into consideration in future natural hazard planning in this area.s. This research was partially funded by projects CGL 2011-23857, ESP2013-47780-C2-2-R and CGL2013-47412-C2-1-P (Spanish Ministry of Economy and Competitiveness).Peer reviewe

RESCUhE Project: Cultural Heritage vulnerability in a changing and directional climate

[EN] RESCUhE Project (Improving structural RESilience of Cultural HEritage to directional extreme hydro-meteorological events in the context of the Climate Change) is a coordinated IGME-UAM research project funded by Spanish Government (MCIN/AEI/10.13039/501100011033). The framework of this research is the predicted increase in climate change vulnerability of heritage sites and the current disconnection between both environmental research on material decay and the practical aspects of designing preventive conservation measurements.RESCUhE Project (Improving structural RESilience of Cultural HEritage to directional extreme hydro-meteorological events in the context of the Climate Change) is a coordinated IGME-UAM research project funded by Spanish Government (MCIN/AEI/10.13039/501100011033).Peer reviewe

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016

How does anisotropy in bedrock river granitic outcrops influence pothole genesis and development?

Pothole formation and development may be influenced by joint sets and other heterogeneities within bedrock, as well as by hydraulics. Previous research indicates that most potholes found in rivers of the mountainous Spanish Central System exhibit preferred orientations associated with dominant joints and correlate more strongly with variations in substrate resistance than with hydraulics. Weathering and erosion weaken rock surfaces, which leads to decreased mechanical resistance. We start from the hypothesis that different mechanisms of pothole formation may create around the pothole a distinctive signature in terms of ultrasound pulse velocity and surface hardness. We develop a conceptual model and test it using potholes for which we know the mechanism of formation, demonstrating that the spatial and statistical distributions of dynamical mechanical properties and surface hardness of a pothole may provide insight into its genesis. Copyright © 2016 John Wiley & Sons, Ltd.This research was partially funded by Geomateriales 2 programme (S2013/MIT-2914) funded by the Regional Government of Madrid (Spain).Peer reviewe

Erosional transition of shoreline blocks by lichen colonization in Cantabria associated to the end of the LIA

20th Congress of the International Union for Quaternary Research (INQUA). Dublin, 25th and 31st July 2019, AbstractLichen colonization of surface rocks depends strongly of the environmental conditions and nutritional disposal, mainly nitrogen and carbon dioxide. The presence of lichens could accelerate the surface erosion by chemical weathering, although they could prevent mechanical erosion as well. Lichen covering prevent for this erosion except in the case of strong eolian weathering, where multiple impacts of grain-sized particles avoid the lichen growth. The presence of carbonate megablocks along the shoreline between Santander and Bilbao (Cantabria domains, north of Spain) exhibit different overlapping of erosional processes. These blocks show ventifacts (groove marks) along the external surface related to strong winds hitting with airborne quartz grains, and which size ranging between 0.1-0.3 mm. The present wind-blow trending in the coastal range is W-NW, which is coincident with the ventifacts arrangement and orientation. Overlapping to the ventifacts, we can observe a chemical weathering of the aeolian-polished sides of the blocks, and in different patches with centimetric extension and depth. We can observe that the wind-struck boulder-side has been colonized by calcicolous lichen specie, Verrucaria maura (tar lichen). This lichen is sea-spray resistant and its annual growth rate has been calibrated from cemeteries close to the shoreline, having similar environmental conditions that in the coast (precipitation and temperature). The lichen colonization of these beach boulders indicates a period of weak aeolian abrasion and prevalent chemical weathering. We assume that this fluctuating erosional process is directly related to a change in the climatic conditions during the LIA ending times affecting rainfall, humidity and therefore wind entrainment of sand grains affecting the shoreline. The oldest lichen measured in these blocks suggests that the end of the LIA could be in the year 1855 ± 6 yr. NAO variations and the annual precipitation curve in the area during the last 300 yr. support this data.Instituto Geológico y Minero de España, EspañaUniversidad Autónoma de Madrid, EspañaUniversidad del País Vasco, Españ

The use of multiscale 3D digital models for non-destructive morphological measurements on sculpted bedforms: implications for erosion and weathering models in bedrock rivers in protected areas

Trabajo presentado en el Japan Geoscience Union Meeting, celebrado en Chiba (Japón), del 20 al 25 de mayo de 2017Rock surfaces are the most sensitive portion to weathering an erosion processes, and therefore, a detailed analysis of surface morphologies is of paramount importance. This importance increases when dealing with heritage sites, such as geosites, cultural heritage sites or any other relevant rock outcrop in protected areas, as sometimes a relatively small surface change may lead to a significant loss of aesthetic or scientific values. There are number of non-destructive techniques to characterise surface morphology to various scales. This communication describes surface morphologies at different scales on the river bed of the Manzanares, a bedrock reach located in “La Pedriza”; within the National Park of Sierra de Guadarrama (Central Spain). “La Pedriza” constitutes the largest granitic outcrop in Europe and a place of historic importance for the development of the geology both in Spain and globally. The studied portion is a place of particular geological interest where the erosion generated by the river reveals a series of microdioritic dikes intruding a coarse-grained Variscan leucogranite. This lithological combination generates dissimilar patterns in terms of weathering and erosion. Surface morphology analysis was made by means of 3D digital models obtained at different scales, from metric scale acquired with photogrammetry from a drone to micrometric scale obtained with a Innowep-TRACEiT surface roughness tester. Combining the results of these techniques relationships between roughness at different scales and erosion-weathering balance were determined as well as the main processes involved in surface weathering and erosion. The resulting features at various scales were identified and its relation to flow patterns and the response of different substrate lithologies to river flow.Research funded by Madrid’s Regional Government project Geomateriales 2 S2013/MIT-2914Peer reviewe

Cambios recientes en el patrón de inundaciones en la rambla de Nogalte (Murcia)

Reunión Nacional de Geomorfología (14ª. 2016. Málaga)En 2012 tuvo lugar en la rambla de Nogalte una avenida que alcanzó su parte baja y el abanico aluvial. Las avenidas en ésta zona han sido habitualmente de carácter muy leve, predominando la anegación de extensas áreas, incluso en grandes crecidas históricas como la de 1973.Departamento de Geología y Geoquímica, Universidad Autónoma de Madrid, EspañaDepartamento de Geodinámica, Universidad Complutense de Madrid, EspañaInstituto Geológico y Minero de España, EspañaInstituto de Geociencias, Consejo Superior de Investigaciones Científicas, EspañaInstituto de Geociencias, Universidad Complutense de Madrid, Españ

Morphometric measurements of bedrock rivers at different spatial scales and applications to geomorphological heritage research

Abstract Morphometric characterisation is particularly relevant in the study of geomorphological heritage. 3D modelling techniques have been proven as very useful tools to recognise, characterise and valorise geomorphosites. Bedrock rivers account for one of the most outstanding aspects within geomorphological heritage due to the amount of distinctive and attractive geomorphological features associated to them and the high preservation of sculpted forms. Digital elevation models (DEMs) have made it increasingly possible to establish accurate morphometric indices and establish clearer connections between forms and processes. This paper reviews different methodologies to obtain DEMs on bedrock rivers. This review goes from DEM analysis at multiple spatial scales to introduce optical microrugosimeter as the latest technical development to facilitate micromorphometric analysis. Micromorphometric analysis opens the scope for improving the knowledge we have on trans-scale issues in bedrock rivers. Micromorphometric analysis also opens a new layer of information that enriches the public’s valuation of geodiversity of geomorphosites by increasing its didactic and interpretative potential

Sediment Response after Wildfires in Mountain Streams and Their Effects on Cultural Heritage: The Case of the 2021 Navalacruz Wildfire (Avila, Spain)

The 2021 Navalacruz wildfire occurred in a mountainous area in the Sistema Central (Spain). Despite having an average low severity index (dNBR), the loss of vegetation cover associated with the fire was responsible for a high rate of sedimentation in the rivers and streams. Additionally, the burned area affected up to 60 cultural heritage sites, including archaeological and ethnological sites, and damage ranged from burnt pieces of wood to the burial of archaeological sites. In the present work, we document and analyze the post-fire evolution in several rivers and streams. This is based on a field survey of infiltration rates, hydrodynamic modeling, and the study of channel morphological changes. Our analysis revealed how the first post-fire rains caused the mobilization and transport of ashes. This created hydrophobicity in the soils, resulting in large amounts of materials being transported to rivers and streams by subsequent medium- and low-magnitude storms. A hydrological and hydraulic model of the study catchments under pre- and post-fire conditions suggests that these trends are a consequence of a post-fire increase in flow rates for similar rainfall scenarios. In this respect, our estimates point at a significant increase in sediment transport capacities associated with this post-fire increase in flow rates. The combination of locally steep slopes with high-severity fire patches, and a considerable regolith (derived from pre-fire weathering), resulted in a series of cascading responses, such as an exacerbated supply of sand to the drainage network and the triggering of debris flows, followed by erosion and entrenchment