Innovación en la producción de cart ografa...

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XIV Reunión Nacional de Geomorfología. Málaga 2016 XIV Reunión Nacional de Geomorfología. Málaga 2016

Innovación en la producción de cartografía geomorfológica de amplias y variadas superficies. Ecuador, un caso de éxito

Innovative geomorphological cartography generation of large and varied land areas. Ecuador, a

success story

I. Barinagarrementeria1 y A. Leránoz2 1 Dpto.Sistemas de Información Territorial, Tracasa, C/ Cabárceno 6, 31621 Sarriguren (Navarra). [email protected] 2 Dpto.Sistemas de Información Territorial, Tracasa, C/ Cabárceno 6, 31621 Sarriguren (Navarra). [email protected] Resumen: Los grandes proyectos de generación de cartografía geomorfológica demandan producir más superficie, en menos tiempo y con una calidad similar o incluso superior con respecto a cartografías tradicionales, de ahí que las metodologías y herramientas hayan aprovechado las nuevas tecnologías a su alcance para lograr este objetivo. El objetivo de este trabajo es presentar una nueva forma de producir cartografía geomorfológica, innovadora en cuanto a los modelos, herramientas y metodologías, utilizada con éxito en el proyecto de Levantamiento de Cartografía Geomorfológica a escala 1:25.000 de Ecuador realizado en el marco del Programa SIGTIERRAS del Ministerio de Agricultura, Ganadería, Acuacultura y Pesca del Ecuador. Se han generado 122.000 Km2 de cartografía geomorfológica como insumo principal del levantamiento geopedológico, categorizando el territorio a través de un sistema jerárquico en unidades que presentan rasgos comunes, en un país que destaca por su gran diversidad geomorfológica por estar dividida en 3 regiones completamente diferentes: Costa, Sierra y Amazonía. Para abordar este gran reto se definen 221 unidades geomorfológicas y se planifican 81 salidas de campo donde se visitan y describen mediante ficha de campo digital incorporado en la Table/PC miles de puntos dispersos en el territorio ecuatoriano. Además, se diseña un sistema de trabajo basado en la tecnología ARCSDE y se apuesta por un software de trabajo innovador asentado sobre 3 pilares: 1) ArcGis; 2) Purview que proporciona visión estereo-sintética general del terreno en contraposición a los softwares tradicionales de estereoscopía; y 3) Vector Factory que facilita la búsqueda y el almacenamiento de los datos y ofrece de procesos de control de calidad internos. También se implementan programas de captura de datos, control de calidad etc. En total se generan 365 hojas de cartografía geomorfológica 1:50.000, 365 salidas gráficas, una por cada hoja 1:50.000 y 105 salidas gráficas y memorias técnicas, una por cantón. Todo ello ejecutado en un año y medio de plazo. Palabras clave: ArcSDE, cartografía, Ecuador, geomorfología, visión estéreo-sintética, Abstract: Large geomorphological cartography generation projects demand to produce more land in less time and with a similar or even higher quality, therefore the tools and methodologies developed, have taken advantage of the new technologies within reach to achieve this goal. The aim of this document is to show a new way to produce geomorphological cartography, innovative in terms of models, tools and methodologies and that have been successfully used for the Geomorphological Mapping project, on 1:25.000 scale of Ecuador is produced under the Ministry of Agriculture, Livestock, Aquaculture and Fishing of Ecuador SIGTIERRAS Programme. As the main source for geopedological mapping, 122.000 km² of geomorphological cartography have been generated, organizing land into a hierarchical system of units that have common features, in a country where its great geomorphological diversity is especially noteworthy, since it is divided in three completely different regions: Coast, Mountain range and Amazon forest. To address this great challenge 221 geomorphological units are defined and 81 field trips are planned where points in the field were visited and described by a Digital Field Data tab included in a Tablet/PC thousands of points spread throughout Ecuador. Moreover, a working system is designed based on ARCSDE technology and are committed to the use of innovative software resting on three pillars: 1) ArcGis; 2) Purview, providing stereo-synthetic vision as a general view of the ground, as opposed to conventional stereoscopy softwares; and 3) Vector Factory, allowing easy search and data storage and offering internal quality processes. In addition, data entry programs are implemented, quality control, etc. In total, 365 geomorphological cartography sheets on 1:50.000 scale, 365 graphic outputs for each 1:50.000 sheet and 105 graphic outputs and technical reports, one per canton. All of this has been achieved in only one and a half years. Keywords: ArcSDE, cartography, Ecuador, geomorphology, stereo-synthetic vision,

GIS approximation of how land use/cover changes affect the hydrological system in a mediterranean mountain catchment

Una aproximación SIG de la afección producida por los cambios de uso del suelo en un sistema hidrológico de una cuenca mediterránea de montaña

I. Lizaga 1, L. Quijano1, L. Palazón 1, L. Gaspar 2, A. Navas 1

1 �Dpto.�Suelo�y�Agua,�Estación�Experimental�de�Aula�Dei,�CSIC,�Avenida�Montañana,�1005,�50059�Zaragoza�(España).�[email protected] [email protected]; [email protected]; [email protected]

2 �Museo�de�Ciencias�Naturales,�CSIC,�Calle�de�José�Gutiérrez�Abascal,�2,�28006�Madrid�(España).�[email protected]

Abstract: Land use and land cover patterns are linked to natural and anthropogenic activities. Particularly,�in�the�mediterranean�region,�the�development�of�agriculture�with�a�long�history�of�cultivation�is�associated�with�many�significant�changes�in�the�original�landscape.�During�recent�decades,�most� changes� in�Mediterranean�agroecosystems�are� linked� to� the� rapid�expansion�of�crops and on the other side the abandonment of agricultural lands. In Spain land abandonment has�particularly�increased�since�the�1960s�as�a�consequence�of�complex�socio-economic�factors�leading to depopulation of rural areas.

Agriculture� intensification� in� mediterranean� agroecosystems� and� posterior� land� abandonment�and� reforestation� have� significantly� affected� the� hydrological� behavior� and� the� connectivity�patterns�thus�information�on�the�spatial�distribution�of�land�use/cover�is�essential�for�monitoring�the runoff response to interpret catchment hydrology. In this study, a medium size catchment (23 km2)�located�in�the�central�part�of�the�Ebro�Basin�in�the�north-east�of�Spain,�representative�of�Mediterranean�mountain�agroecosystems�was�selected�to�assess�the�effect�of�land�use/cover�changes�during�the�last�decades�on�the�hydrological�network�in�the�catchment.�The�present�study�evaluates�the�spatio-temporal�changes�of�land�use/cover�in�the�Vandunchil�stream�catchment�over�a�period�of�55�years.�To�this�purpose�remote�sensing�techniques�for�land�use�change�detection�by�using aerial photographs are used to understand the landscape dynamic.

Key words: digital techniques, hydrological network, land abandonment, mediterranean agroecosystems, natural revegetation.

Resumen: Los patrones de la cubierta vegetal y los diferentes usos del suelo se encuentran ligados a las actividades antropogénicas. Particularmente, en la región el desarrollo de la agricultura en la región mediterránea ha producido enormes cambios en el paisaje, y con ello en la conectividad hidráulica y su distribución. Estos ecosistemas fueron sometidos a una gran presión agrícola, la cual a partir de los años sesenta comenzó a abandonarse. Este abandono de los terrenos agrícolas produjo la revegetación natural de los campos de cultivo y la recuperación del bosque mediterráneo. Todo esto unido a los planes de reforestación llevados a cabo en estas áreas ha restaurado gran parte de la conectividad hidráulica natural reduciendo enormemente la escorrentía.

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En este estudio se ha seleccionado una cuenca de tamaño medio (23Km2) representativa de los agroecosistemas montañosos mediterráneos situada en la parte central de la cuenca del río Ebro al noreste de España. Esta cuenca fue seleccionada con el objetivo de estudiar y cuantificar la diferencia de la conectividad hidráulica a causa del cambio en los usos del suelo de las últimas décadas. Para el desarrollo de este trabajo, se utilizaron técnicas de teledetección y fotografías aéreas de diferentes épocas. En el presente estudio se evalúan los cambios espacio-temporales producidos por los cambios en la cubierta vegetal de la cuenca del barranco Vandunchil en un periodo de 55 años.

Palabras clave: abandono de tierras, revegetación natural, red hidrológica, técnicas digitales, agroecosistemas Mediterráneos.

INTRODUCTION

Sediment connectivity has an important effect on the development of morphological landform features being one of the greatest conditioning factors on the development of hydrological networks. Sediment connectivi-ty�have�a�great�influence�on�how�sediment�is�moved and relocated, modifying the current landscape and determining the spatial distri-bution�of�sources�and�sinks�of�water�(Puigde-fabregas et al., 1999).

Soil erosion and hydrological connectiv-ity is greatly responsive to land use (García-Ruiz, 2010; Kosmas et al., 1997; Mohammad and Adam, 2010; Nunes et al., 2011)and is not only closely related to geoecological fac-tors (lithology, topography, and climatology. Humankind rather than natural forces are the source of most contemporary changes in land-cover�(Meyer�and�Turner,�1994).�Agricultural�deforestation and changes in land use have generally been considered a local environ-mental issue, but it is becoming an important global problem (Foley et al., 2005).

The� literature� has� shown� an� increasing�attention to the linkage between areas with different hydrological behavior and land use, with particular focus on the connection be-tween�hillslopes�and�channels�(Cavalli�et al., 2013) and modelling the different process of

hillslope instability (Heckmann and Schwang-hart, 2013) geomorphic coupling and (sedi-ment.

�The�problem�of�steep�slope�agriculture�has�changed connectivity and erosion rates during the last centuries in Mediterranean landscapes. In�this�investigation�we�assess�an�approxima-tion to the variation of connectivity produced by land cover changes during the last 50 years. As�a�consequence�of�complex�socio-economic�and environmental factors such as the depop-ulation of rural areas and the impossibility of mechanization in steep terrain, land abandon-ment has occurred since the 1960s (Quijano, 2016). In addition, subsequent reforestation during� the� 70� and� 80’s� caused� a� large� im-pact on runoff reduction due to afforestation (Buendia�et al.,�2016).�The�aim�of�this�study�is�to approach how land cover change affects hy-drological behavior in a middle size mountain Mediterranean catchment.

STUDY AREA

The� study� area� is� located� in� the�Vandun-chil stream valley within the central part of the Ebro�Basin�in�the�North-east�of�Spain�(Figure�1a). From the geological point of view it is located�on�the�distal�part�of�the�Pre-Pyrenean�range with characteristically S-SW low bed-ding�between�5�-�8�degrees.�The�rock�outcrops�in the study area include two conformable

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Oligo� -� Miocene� lithostratigraphic� units� of�the�Uncastillo�Formation�composed�by�sand-stones,�claystones�and�siltstones.�The�geomor-phological setting is clearly conditioned by the low bedding strata.

XIV Reunión Nacional de Geomorfología. Málaga 2016 Introduction

Sediment connectivity has an important effect on the development of morphological landform features being one of the greatest conditioning factors on the development of hydrological networks. Sediment connectivity have a great influence on how sediment is moved and relocated, modifying the current landscape and determining the spatial distribution of sources and sinks of water (Puigdefabregas et al., 1999).

Soil erosion and hydrological connectivity is greatly responsive to land use (García-Ruiz, 2010; Kosmas et al., 1997; Mohammad and Adam, 2010; Nunes et al., 2011). Humankind rather than natural forces are the source of most contemporary changes in landcover (Meyer and Turner, 1994). Agricultural deforestation and changes in land use have generally been considered a local environmental issue, but it is becoming an important global problem (Foley et al., 2005). Soil erosion is directly related to the loss of soil nutrients in the topsoil resulting in soil degradation, which, in turn, leads to reduced soil productivity and increased soil erodibility (Quijano et al., 2016). Furthermore, depletion of soil depth in agroecosystems can be a serious threat to agricultural sustainability (Fornes et al., 2005).

The literature has shown an increasing attention to the linkage between areas with different hydrological behavior and land use, with particular focus on the connection between hillslopes and channels (Cavalli et al., 2013) and modelling the different process of hillslope instability (Heckmann and Schwanghart, 2013).

The problem of steep slope agriculture has changed connectivity and erosion rates during the last centuries in Mediterranean landscapes. In this investigation we assess an approximation to the variation of connectivity produced by land cover changes during the last 50 years. As a consequence of complex socio-economic and environmental factors such as the depopulation of rural areas and the impossibility of mechanization in steep terrain, land abandonment has occurred since the 1960s (Quijano, 2016). In addition, subsequent reforestation during the 70 and 80’s caused a large impact on runoff reduction due to afforestation (Buendia et al., 2016). The aim of this study is to approach how land cover change affects hydrological

behavior in a middle size mountain Mediterranean catchment.

Study Area

The study area is located in the Vandunchil stream valley within the central part of the Ebro Basin in the North-east of Spain (Figure 1a). From the geological point of view it is located on the distal part of the Pre-Pyrenean range with characteristically S-SW low bedding between 5 - 8 degrees. The rock outcrops in the study area include two conformable Oligo - Miocene lithostratigraphic units of the Uncastillo Formation composed by sandstones, claystones and siltstones. The geomorphological setting is clearly conditioned by the low bedding strata.

FIGURE 1. (a) Location of the study catchment in the central part of the Ebro Basin (NE Spain). (b) Detailed orthophoto of Vandunchil Catchment. Red square delimits visualization of Figures 3-4. Materials and methods

FIGURE� 1.� (a) Location of the study catchment in the central part of the Ebro Basin (NE Spain). (b) Detailed orthophoto of Vandunchil Catchment. Red square delimits visualization of Figures 3-4

MATERIALS AND METHODS

The� assessment� of� sediment� connectivi-ty was carried out by applying topography - based� index� complemented� by� two� land� use�maps�for�1957�and�2012.�A�first�map�was�cre-ated�by�an�orthorectification�of�the�American�army aerial photographs 1957 using a super-vised�classification� in�ERDAS�after�a�photo-graphic� enhancement.� The� current� map� was�

digitalized� over� 2012� PNOA� orthophotogra-phy�and�field�work�maps.�

Sediment connectivity was estimated us-ing a numerical modeling approach to sim-ulate how connectivity changes due to the different�land�covers.�Coupling�behavior�has�a great effect on how the systems respond to disturbance. Hence it is really important to determine how the system connectivity responds to human induced cover changes (Harvey, 2002)based mainly on previous-ly� published� work.� Coupling� mechanisms�link� the� components� of� the� fluvial� system,�controlling sediment transport down the system and the propagation of the effects of� base-level� change� up� the� system.� They�can be viewed at several scales: at the lo-cal scale involving within-hillslope cou-pling, hillslope-to-channel coupling, and within-channels, tributary junction and reach-to-reach coupling. At larger scales, coupling can be considered as zonal cou-pling, between major zones of the system or as regional coupling, relating to complete drainage�basins.�These�trends�are�illustrated�particularly� by� the� examples� of� hillslope-to-channel coupling in the Howgill Fells, northwest England, badland systems in southeast�Spain,�alluvial�fans�in�Spain,�USA�and�UAE,�and�base-level-induced�dissection�of Neogene sedimentary basins in southeast Spain. As the spatial scales increase, so do the timescales involved. Effective temporal scales relate to magnitude and frequency characteristics, recovery time and propa-gation time, the relative importance chang-ing with the spatial scale. For downsystem coupling�at�the�local�scale,�the�first�two�are�important, with propagation time increas-ing in importance in larger systems, espe-cially in those involving upsystem coupling related� to� base-level� change.� The� effective�timescales range from the individual event, with a return period of decades, through

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decadal to century timescales for downsys-tem coupling, to tens to hundreds of thou-sands of years for the basinwide response to base-level�change.�The�effective�timescales�influence� the� relative� importance� of� fac-tors controlling landform development.”,”-DOI”:”10.1016/S0169-555X(01.� For� this�reason� we� used� the� connectivity� index� (1)�proposed� by� (Borselli� et� al.,� 2008)one� (IC�using�the�C-factor�from�RUSLE�as�a�weight�factor (W)�in�the�index.

XIV Reunión Nacional de Geomorfología. Málaga 2016 The assessment of sediment connectivity was carried out by applying topography - based index complemented by two land use maps for 1957 and 2012. A first map was created by an orthorectification of the American army aerial photographs 1957 using a supervised classification in ERDAS after a photographic enhancement. The current map was digitalized over 2012 PNOA orthophotography and field work maps.

Sediment connectivity was estimated using a numerical modeling approach to simulate how connectivity changes due to the different land covers. Coupling behavior has a great effect on how the systems respond to disturbance. Hence it is really important to determine how the system connectivity responds to human induced cover changes (Harvey, 2002). For this reason we used the connectivity index (1) proposed by (Borselli et al., 2008) using the C-factor from RUSLE as a weight factor (W) in the index.

�� (1)

Where �� and �� are the upslope and downslope component defined by:

�� √� (2)

where W is the average weighting factor of the upslope contributing area, S is the average slope gradient of the upslope contributing area (m/m) and A is the upslope contributing area (m2).

�� ∑ �� (3)

where �� is the length of the flow path along each i cell according to the steepest downslope direction (m), �� and �� are the weighting factor and the slope gradient of the i cell, respectively.

Borselli et al. (2008) proposed � � �� including 0.005 as the minimum slope value to avoid infinitive values in equation (2). Following the methodology applied by Cavalli et al. (2013) we preserved the original values of our 2m DEM to obtain more realistic results. In equations (2) and (3) we used our two land use maps (C-factor) as weighting factor

to show the differences between both land uses (1957 and 2012) and how the connectivity index changes over time. To facilitate the visualization we selected the same area as Figure 3 to show how connectivity has changed over 50 years due to land cover modifications.

Results

Steep slope terraces are usual in mountain agroecosystems for rudimentary agriculture. Near-absence tectonic in Vandunchil Catchment determined low dip strata resulting an easy farmable terrain for rudimentary agriculture. Steep slope agriculture not only increases erosion and runoff ratios on the hillslopes but also produces slope instability fostering the probability of mass movements due to the absence of vegetation cover that protects the soil from erosion (Figure 2).

FIGURE 2. (a) Elongated slide-flow-type slope movement detected on 1957 aerial photography, likely developed during a storm event and favored by the absence of vegetation cover, high slope and the upper dryland crops. (b) Same area, now stabilized by the revegetated cover.

(1)

Where and are the upslope and downslope component�defined�by:



�� (1)


�� √� (2)


�� ∑ �� (3)




Results



(2)

where W is the average weighting factor of the upslope contributing area, S is the average slope gradient of the upslope contributing area (m/m)�and�A is the upslope contributing area (m2).



�� (1)


�� √� (2)


�� ∑ �� (3)




Results



(3)

where� is� the� length� of� the� flow� path�along each i cell according to the steep-est downslope direction (m), and are the weighting factor and the slope gradient of the i cell, respectively.

Borselli� et al. (2008)� one� (IC� proposed�including 0.005 as the minimum slope value to�avoid�infinitive�values�in�equation�(2).�Fo-llowing�the�methodology�applied�by�Cavalli�et�al. (2013) we preserved the original values of our 2m DEM to obtain more realistic results. In equations (2) and (3) we used our two land use� maps� (C-factor)� as� weighting� factor� to�show the differences between both land uses

(1957 and 2012) and how the connectivity in-dex�changes�over�time.�To�facilitate�the�visua-lization we selected the same area as Figure 3 to show how connectivity has changed over 50 years�due�to�land�cover�modifications.

Results

Steep slope terraces are usual in mountain agroecosystems for rudimentary agriculture. Near-absence� tectonic� in� Vandunchil� Catch-ment determined low dip strata resulting an easy farmable terrain for rudimentary agricul-ture. Steep slope agriculture not only increases erosion and runoff ratios on the hillslopes but also produces slope instability fostering the probability of mass movements due to the ab-sence of vegetation cover that protects the soil from erosion (Figure 2).



�� (1)


�� √� (2)


�� ∑ �� (3)




Results



FIGURE�2.�(a) Elongated slide-flow-type slope movement detected on 1957 aerial photography, likely developed during a storm event and favored by the absence of vege-tation cover, high slope and the upper dryland crops. (b) Same area, now stabilized by the revegetated cover

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XIV Reunión Nacional de Geomorfología. Málaga 2016

FIGURE 3. (a) 1957 Aerial photograph. (b) 2012 Orthophotography (c) Land cover map developed using a supervised classification of (a). (d) Land cover map of (b) completed in field work. Cultivated land (C), Mediterranean forest (Mf) Reforestation forest (Rf) Abandoned agriculture (Aa).

The total crop area percentages in both years are 12.3 km2 and 3.8 km2 for 1957 and 2012, respectively being 53% and 16% of the total area (23 Km2) of the Vandunchil Catchment.

Figure 3a shows a classic example of steep slope agriculture with almost 70% of the slopes and stream terraces cultivated. Conversely Figure 3b shows an important modification caused by reforestation and the steep slope cover by scrublands. It has been shown that badlands and severely eroded areas have a higher degree of connection than agricultural forest and scrubland (Palazón and Navas, 2014).

Connectivity index with different land covers as a weight factor show an approximation of the effect of human activity over the study area. In Figure 4 it can be easily recognized the decrease on runoff due to new covers as natural revegetation, abandoned fields and the great variation induced by reforestation.

In headwater fluvial catchments the more relevant aspect of coupling is connection between hillslope and channel, i.e. hillslope-channel coupling (Harvey, 2002). Connectivity and slope are essential for coupling development. With the modification in land cover, mostly in reforestation areas, reduction on overland flow might interfere reducing sediment displacement and probably centralizing highest connectivity and erosion areas in streams that remain coupled (yellow-green streams inside afforestation areas in Fig 4).

The treetops minimize the kinetic energy of the raindrops preventing soil detachment (De Luna et al., 2000). Besides, the vegetation cover improves soil quality, by favouring infiltration and preventing runoff. On the contrary, high erosion rates and the low slope resistance could easily produce mass and flow-type slope movements (Figure 3). These fed large volumes of sediment into the stream system.

FIGURE�3.�(a) 1957 Aerial photograph. (b) 2012 Orthophotography (c) Land cover map developed using a supervised classification of (a). (d) Land cover map of (b) completed in field work. Cultivated land (C), Mediterranean forest (Mf) Reforestation forest (Rf) Abandoned agriculture (Aa)

The� total� crop� area� percentages� in� both�years are 12.3 km2 and 3.8 km2 for 1957 and 2012,�respectively�being�53%�and�16%�of�the�total area (23 km2) of the Vandunchil catch-ment.

Figure� 3a� shows� a� classic� example� of�steep� slope� agriculture� with� almost� 70%� of�the�slopes�and�stream�terraces�cultivated.�Con-versely Figure 3b shows an important modi-fication�caused�by�reforestation�and�the�steep�slope cover by scrublands. It has been shown that badlands and severely eroded areas have a higher degree of connection than agricultur-al� forest� and� scrubland� (Palazón� and�Navas,�2014).�

Connectivity� index� with� different� land�covers�as�a�weight�factor�show�an�approxima-

tion of the effect of human activity over the study�area.�In�Figure�4�it�can�be�easily�recog-nized the decrease on runoff due to new covers as�natural�revegetation,�abandoned�fields�and�the great variation induced by reforestation.

In� headwater� fluvial� catchments� the� more�relevant aspect of coupling is connection be-tween hillslope and channel, i.e. hillslope-chan-nel� coupling� (Harvey,�2002).�Connectivity�and�slope are essential for coupling development. With� the�modification� in� land�cover,�mostly� in�reforestation�areas,� reduction�on�overland�flow�might interfere reducing sediment displacement and probably centralizing highest connectivity and erosion areas in streams that remain coupled (yellow-green streams inside afforestation areas in�Fig�4).�

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The�treetops�minimize�the�kinetic�energy�of the raindrops preventing soil detachment (De Luna et al.,�2000).�Besides,� the�vegeta-tion cover improves soil quality, by favour-ing� infiltration� and� preventing� runoff.� On�

the contrary, high erosion rates and the low slope resistance could easily produce mass and� flow-type� slope�movements� (Figure� 3).�These�fed�large�volumes�of�sediment�into�the�stream system.

Comparing� both� IC�output�map� and� land�cover�maps�(Figure�4)�it�can�be�seen�the�impor-tance of land cover for preventing runoff and the� benefits� of� landscape� restoration.� Strong�changes�in�reforestation�cover�in�the�IC�maps,�land abandonment, natural revegetation and especially the reversal to Mediterranean forest have a great effect on the loss of coupling as a consequence on the decrease of runoff.

CONCLUSION

Land� use/cover� changes� by� human� inter-vention, have probably increased connectivity and� runoff� in�Vandunchil�Catchment,�mostly�due to tillage and soil loss whilst abandoned arable lands and reforestation areas seems to be�very�efficient� in� reducing�runoff�and�con-nectivity.� Besides� reforestation� works� have�

reduced the connectivity that probably has contributed to limit soil erosion.

Likely human land cover changes were fa-vored by the low dip of the strata, which created natural terraces easily farmable for rudimentary agriculture. Nowadays the loss of steep slope agriculture and the searching for more propi-tious an easier agriculture lands are reducing runoff in mountain catchments but also produc-ing abandonment of rural communities.

REFERENCES

Borselli,�L.,�Cassi,�P.,�Torri,�D.,�2008.�Prole-gomena�to�sediment�and�flow�connectivity�in� the� landscape:�A�GIS�and�field�numer-ical assessment. CATENA� 75,� 268–277.�doi:10.1016/j.catena.2008.07.006

XIV Reunión Nacional de Geomorfología. Málaga 2016

FIGURE 4. Connectivity index for 1957 and 2012. These figures correspond to the red square on Figure 1 to improve visualization of a representative part of the catchment affected by changes in land cover.

Comparing both IC output map and land cover maps (Figure 4) it can be seen the importance of land cover for preventing runoff and the benefits of landscape restoration. Strong changes in reforestation cover in the IC maps, land abandonment, natural revegetation and especially the reversal to Mediterranean forest have a great effect on the loss of coupling as a consequence on the decrease of runoff.

Conclusion

Land use/cover changes by human intervention, have probably increased connectivity and runoff in Vandunchil Catchment, mostly due to tillage and soil loss whilst abandoned arable lands and reforestation areas seems to be very efficient in reducing runoff and connectivity. Besides reforestation works have reduced the connectivity that probably has contributed to limit soil erosion.

Likely human land cover changes were favored by the low dip of the strata, which created natural terraces easily farmable for rudimentary agriculture. Nowadays the loss of steep slope agriculture and the searching for more propitious an easier agriculture lands are reducing runoff in mountain catchments but also producing abandonment of rural communities.

Bibliography

Borselli, L., Cassi, P., Torri, D., 2008. Prolegomena to sediment and flow connectivity in the landscape: A GIS and field numerical assessment. CATENA 75, 268–277. doi:10.1016/j.catena.2008.07.006

Buendia, C., Batalla, R.J., Sabater, S., Palau, A., Marcé, R., 2016. Runoff Trends Driven by Climate and Afforestation in a Pyrenean Basin. Land Degrad. Dev. 27, 823–838. doi:10.1002/ldr.2384

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FIGURE�4.�Connectivity index for 1957 and 2012. These figures correspond to the red square on Figure 1 to improve visualization of a representative part of the catchment affected by changes in land cover

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