Erosion and Flooding Risks in the Marly Basins of the Eastern Prerif Mountains (Morocco): A Response to Exceptional Climate Events or to Anthropogenic Pressure

Revista de Estudios Andaluces (REA) | Núm. 40, julio (2020) | e-ISSN: 2340-2776. https://dx.doi.org/10.12795/rea.2020.i40 | © Editorial Universidad de Sevilla 2020 https://editorial.us.es/es/revistas/revista-de-estudios-andaluces https://revistascientificas.us.es/index.php/REA CC BY-NC-ND 4.0 159 159 https://dx.doi.org/10.12795/rea.2020.i40.09 Erosion and Flooding Risks in the Marly Basins of the Eastern Prerif Mountains (Morocco): A Response to Exceptional Climate Events or to Anthropogenic Pressure Riesgos de Erosión e Inundaciones en las Cuencas Margosas de las Montañas Prerif Orientales (Marruecos): Una Respuesta a Eventos Climáticos Excepcionales o/a la Presión Antropogénica Abdellatif Tribak [email protected] https://orcid.org/0000-0002-1564-5886 School of Geography. Sidi Mohamed Ben Abdellah University. FLSH –SAIS. BP: 59,Route Immouzer. CP 30000 Fès Maroc. INFO ARTÍCULO ABSTRACT Recibido: 07-04-2020 Revisado: 15-06-2020 Aceptado: 17-06-2020 KEYWORDS Rif Mountains Rainfall severity Anthropogenic Actions Erosion Floods The Eastern Rif Mountains are frequently subject to exceptional rainfall events, whose consequences are sometimes disastrous. The impact of these phenomena on environments is more important as the majorities of slopes are bare and subject to strong human influence. The protective natural forests of the slopes are almost destroyed; they currently cover only a few peaks of mountains in the region. They represent 1.84% of the total area of wadi Tleta sub-basin and only 1.32% of the Tarmast wadi sub-basin. However, croplands, occupying respectively 60% and 34% in the two sub-basins, extend even on the steepest slopes. Similarly, the accelerated and uncontrolled human occupation of the urban peripheries, located downstream of the basins, amplifies the vulnerability of these environments to the hydrological hazards, that threaten several sites surrounding the agglomeration of Taza. Thus, the whole region is subject to different degradation processes. Hydric erosion affects the majority of the slopes; it causes excessive sediment production that may exceed 60 t ha-1 year-1 in some sub-basins. Similarly, flood disasters are quite common in the region. The flood of 20/9/2000 is a reference, with a volume estimated at 4 million m3(DRH-Sebou 2000). Human and material damage was enormous in the rural centers and in the northern outlying districts of Taza. This contribution aims to present and analyze the combined impacts of the extreme rains and the actions of the human societies on the dynamics of the prerifain environment and its adjoining spaces. PALABRAS CLAVE RESUMEN Montañas Rif Severidad de la lluvia Acciones antropogénicas Erosión Inundaciones Las montañas del este del Rif están frecuentemente sujetas a eventos de lluvia excepcionales, cuyas consecuencias son a veces desastrosas. El impacto de estos fenómenos en los entornos es muy importante ya que la mayoría de las pendientes son desnudas y están sujetas a una fuerte influencia humana. Los bosques naturales protectores de las laderas están casi destruidos; actualmente cubren solo unos pocos picos de montañas en la región. Representan el 1.84% del área total de la subcuenca del wadi Tleta y solo el 1.32% de la subcuenca del wadi Tarmast. Sin embargo, las tierras de cultivo, que ocupan respectivamente el 60% y el 34% en las dos subcuencas, se extienden incluso en las pendientes más empinadas. Del mismo modo, la ocupación humana acelerada e incontrolada de las periferias urbanas, ubicadas aguas abajo de las cuencas, amplifica la vulnerabilidad de estos entornos a los riesgos hidrológicos, que amenazan varios sitios que rodean la aglomeración de Taza. Por lo tanto, toda la región está sujeta a diferentes procesos de degradación. La erosión hídrica afecta a la mayoría de las pendientes; causa una producción excesiva de sedimentos que puede superar las 60 t ha-1 año-1 en algunas subcuencas; del mismo modo, los desastres por inundación son bastante comunes en la región. DOI: https://dx.doi.org/10.12795/rea.2020.i40.09 Formato de cita / Citation: Tribak, A. (2020). Erosion and Flooding Risks in the Marly Basins of the Eastern Prerif Mountains (Morocco): A Response to Exceptional Climate Events or to…. Revista de Estudios Andaluces, 40, 159-182. https://dx.doi.org/10.12795/rea.2020.i40.09 Correspondencia autores: abdellatif[email protected] (Abdellatif Tribak). Abdellatif Tribak / REA N. 40 (2020) 159 - 182 160 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 La inundación del 20/9/2000 es una referencia, con un volumen estimado en 4 millones de m3 (DRH-Sebou 2000). El daño humano y material fue enorme en los centros rurales y en los distritos periféricos del norte de Taza. Esta contribución tiene como objetivo presentar y analizar los impactos combinados de las lluvias extremas y las acciones de las sociedades humanas sobre la dinámica de estos ambientes de montaña y sus espacios adyacentes. 1. INTRODUCTION It is certain that interest in natural risks continues to grow on a planetary scale. Indeed, with the climatic variability, well perceptible during the last decades, the world has known incessantly tragic events, having unfortunate consequences. This problem of natural risks is now located at the crossroads of several fields of scientific research; it concerns actors of various natures. Since 1990, the contribution of scientists in the animation of the subject is more and more abundant and important; with a growing influence during this period of the social sciences. Indeed, several methods have been adopted with the aim of reintroducing social and political factors in the analysis of natural disasters, by trying to go beyond the dominant approaches of the earth sciences, focused only on natural phenomena. Hydrous erosion, in all its forms and processes, as well as floods, represent natural calamities that are widespread on the surface of the globe. In relation with recent climatic variability and multiple anthropogenic pressures, these phenomena are more and more frequent and the damage they generate is constantly increasing. By its geographical situation in the Mediterranean basin, Morocco is marked by a strong rainfall irregularity which generates very violent hydrological behaviors, particularly in the catchments characterized by topographical, geological and anthropic factors which accelerate the irregularity of the extreme forms of flow. Thus, despite the global warming and recurring droughts that have characterized the country since the 1980s, exceptional rainfall events are quite frequent in several regions of the country (Ourika 1994, El Hajeb 1997, El Jadida 1996, Taza 1995, 1997, 2000, 2002 and 2010, Mohamedia 2002, Demnat 2005, Nador 2008 and all the North of Morocco in 2009 and 2010, etc). In each episode, huge quantities of water are released in a matter of days or few hours, with very high instantaneous intensities. The succession of such events constitutes a permanent risk that threatens several northern and sometimes some southern provinces (Agadir 2009-2010-2018). Several Moroccan cities have been painfully hit by catastrophic floods during these last decades. The recent case concerns the city of El Jebha, located on the Mediterranean coast in northern Morocco; it suffered a real disaster following floods and catastrophic landslides caused by torrential rain during the afternoon of March 24th, 2020. The frequencies of these phenomena and their serious consequences constitute a crucial problem for sustainable development and regional planning in Morocco. They reflect a high degree of vulnerability which often show human involvement and responsibility for the catastrophic events linked to erosion and flood crises. The Prerif Mountains, carved mainly in tertiary marly rocks and almost completely denuded, are increasingly concerned by such rainy episodes that cause extreme forms of flow leading to intense erosion on the slopes and disastrous floods downstream of the basins. This situation is reinforced by a strong human pressure on the slopes and by an increasingly aggravated occupation of the sites at risk, due to a rapid and uncontrolled urbanization of the peripheral zones of the agglomerations. The concerned area is part of the eastern prerif at the north of Taza, occupying a downstream position within the watersheds of wadi Lahdar, and wadi Larbâa (figure1). It is characterized by a rugged topography of hills and low mountains that offer a pattern of irregular slopes, related to the structural feature and the importance of dissection and quaternary inheritances. The geological context shows a clear predominance of tertiary marly rocks in a structure marked by thrust sheets (Leblanc, 1979). Marly series dated from Cretaceous and especially from the end of the Tertiary, occupy almost all the region. They are partly surmounted by sandstone formations that particularly arm the allochthonous units. The region is evolving in a semi-arid mediterranean climate, associated with a strong irregularity of annual rainfall and seasonal contrasts. Annual averages are 681 mm for the Had Msila station (1970-2016) and 600 mm for the Taza station (1970 -2016). Abdellatif Tribak / REA N. 40 (2020) 159 - 182 161 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 During this period the Taza station recorded maximum annual rainfall reaching 1125 mm in 2009/2010 and a minimum of 275 mm in 1994/1995. Similarly, the Had Msila station recorded a maximum value of 1411mm in the year 2009/2010 and a minimum value of 280 mm during the year 1994/1995. The region is an old demographic home where the settlement is very old (Tribak, 2000). Human densities remain impressive; despite the migratory movements in the last decades, they still exceed the 60 h / km² threshold in all municipalities in the Taineste district (HCP-RGPH, 2004). This human pressure, to which different land-use patterns are linked, explains largely the great variability of environmental degradation phenomena. The overexploitation of cleared land, fueled by a rapidly growing population, explains the extension of crops to areas with steep slopes, resulting in the acceleration of runoff coefficients and erosion processes in this fragile environment. In this rifain area, soil erosion is a crucial problem that threatens the economy of the region and destabilizes the lives of local population, already precarious. It is accelerated following to the clearing of forests that protected sensitive soils. The intense erosion processes on the marly slopes as well as the extremely rapid evolution of the gullies, degrades the soil capital and allows evacuating huge quantities of sediments annually to the main collectors, threatening the road and hydraulic infrastructures, and residential districts. Similarly, the large runoff coefficients, caused on the bare marly slopes during extreme rains, are occasionally favorable to catastrophic floods, which painfully affect the outlying districts of Taza which have developed, in an uncontrolled manner, in the confluence zone of the entire hydrographic network draining the watershed of the wadi Larbâ, and where takes refuge a dense population often in precarious situations. This contribution synthesizes the research work done in the region, during the last two decades, on the phenomena of runoff and erosion. It aims to present and analyze the combined impacts of the extreme rainfall events and the actions of the human societies on the dynamics of the prerifan environment and its Figure 1. Location of the oriental Prerif zone. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 162 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 adjoining spaces. The aim is also to deepen the understanding of the functioning of this environment and to contribute to the various debates and projects concerning regional planning and the fight against disasters caused by natural hazards. The following hypotheses should therefore be emphasized: ‒Multiple human actions accentuate the intrinsic fragility of this environment and consequently, accelerate the irregularity of extreme flows and the aggressiveness of the dynamic processes. ‒The uncontrolled human occupations in the peripheral areas of the cities create new vulnerabilities and amplify the disasters caused by extreme floods. 2. MATERIALS AND METHODS The climate study approach relies on the use of meteorological data relating to a series of rainfall measurements in both Taza and Had Msila station for the period (1970 - 2016). Other climatic data were taken from bibliographical references of previous studies (Tribak, 2000; Tribak, 2002; Tribak, 2007; Tribak, El Garouani & Abahrour, 2012; DRH Sebou, 2000; Akdim, Laaouane, Taous & Obda, 2003; Taous et al. 2010; Abahrour, 2009; Abahrour, 2015). Similarly, time situations were analyzed by referring to the weather maps provided by the German site www.Wetter3.de, which allowed us to follow the temporal evolution of the disturbances during the rainy events. The choice of synoptic situations is made according to the availability of rainfall data and their amount, then to the damage caused during exceptional rainy periods. The analysis concerns the situations at 500 hPa geopotential height compared, in the case of convective episodes, with mapping at a lower geopotential level of 850 hPa. The exploitation of the collected data aims to appreciate in more detail the extreme rainfall parameters which constitute determining elements in the acceleration of the erosion and the genesis of the flooding phenomena. The historical dimension of this study was approached on the basis of bibliographic research. Administrative records and reports from the Urban Agency, the Ministry of Housing and the Office of the High Commissioner for Planning (HCP) have been helpful in supporting our results from the field. Such are the cases for the reports of the Taza province and Urban Agency, and the hydraulic agency of the sebou basin for the year 2000. This work has been supplemented by more spatially and thematically targeted field research. Surveys and fieldwork allowed us to verify and complete the photo-interpretation, concerning details of the natural and anthropogenic causes of erosion and flooding phenomena. Concerning this research component, it is very important to identify the remains of the sediments and the different traces of floods in the affected zones and to interview the local population. These traces provide rich information on flow dynamics and deposition at the time of submersion. In the same way, the interviews with the population inform us about the history of the past floods and the extent of the damage suffered. It is therefore a question of characterizing and classifying the past floods, identified according to the information collected in the field, because it is rare to have sufficient and reliable data on rainfall amounts and flood flows. Thus, flood events classification can be based on spatial extent, damage, casualties, and, if possible, the height reached by the flood during submersion (Akdim et al., 2003., Taous et al., 2010). The only flood, for which we have reliable data, during the last two decades, is that of 20/9/2000 which we have taken as a reference flood. It is considered to be the most serious level of flood hazard and for which more data are available. Exploitation of aerial photographs and satellite images, from different missions, allowed us to map, and support field study results concerning land use, erosion patterns, and the extension of the flood zones downstream of the basins. The interpretation of the aerial photos concerned respectively the missions of 1962 (scale - 1/17500) and 1986 (scale -1/20000). The current land use in the area is carried out from the analysis of the image LandSat of October 8th, 2017 (resolution 30 m) downloaded from the site https:// earthexplorer.usgs.gov. The quantification of the hydric erosion in different sub-basins of the region is carried out by the RUSLE model (Renard, Foster, Weesies, McCool & Yoder, 1997; Bonn, 1998); based on a linear function involving Abdellatif Tribak / REA N. 40 (2020) 159 - 182 163 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 the spatial combination of the different parameters contributing to soil erosion (Lewis, Chen & El Garouani, 2007; El Garouani, Chen, Lewis, Tribak & Abahrour, 2009; Tribak, El Garouani et al., 2009; Arari, Tribak, Amhani & El Ommal, 2019). In this approach, we proceeded to a spatialization of hydrous erosion by considering the parameters that influence erosive dynamics in the concerned basins. It relies on the collection, and the spatial analysis of the data concerning the physical constraints, the land use and the geomorphology of the environments. We, therefore, proceeded by extracting the thematic information from the satellite images (Landsat TM 1987, resolution 30 m and Landsat ETM + /2000 and 2014, resolution 20 m), the soil study in the field and at the laboratory, and the exploitation of a digital terrain model (DTM created from digital topographic maps of the region) and the derived data such as declivity and length of slopes. In this work we used ArcGIS 10.1 software for scanning all required information layers and spatial analysis operations (Lewis et al., 2007). In addition; we used the Erdas Imagine software for the treatment of remote sensing imagery for land use mapping (El Garouani et al., 2009; Tribak, Abahrour, El Garouani, Arari & Amhani, 2017; Arari et al., 2019). The RUSLE model integrated into the Idrisi software allowed us to evaluate the average annual rate of erosion in some sub-basins of the region, according to the distribution of rainfall aggressiveness, soil erodibility, topography, land use and crop management practices (Lewis et al., 2007; El Garouani et al., 2009; Tribak et al., 2009; Tribak et al., 2017; Abahrour, 2009; Arari et al., 2019). According to this model, the erosion rate (A in t ha-1 year-1) is a multiplicative function of rainfall erosivity (R), which is equal to the potential energy, multiplied by the environmental resistance of the erodibility of the soil (K), topographic factor (SL), vegetation cover and cultural practices (C) and anti-erosion practices (P). A = R. K. SL.C.P The R-value used for the study area was based on the Rango & Arnoldus formula (1987) and derived using the 1979-2013 climate data of the regional stations. The aggressiveness of the rains is estimated at 65 The K value was calculated using the Wischmeier nomogram, the soil map of the study area and the infiltration and soil properties of the area, as developed by Tribak 2000, El garouani et al 2009 and Tribak et al. 2009. The K factor values, located between 0.22 and 0.46, show a marked fragility of the soils and their susceptibility to erosion The LS factor is calculated by the GIS Idrisi Andes software. It uses DTM to calculate slope, slope lengths and slope orientation (Lewis et al., 2007; El Garouani et al., 2009). The value of the C factor used is based on results from similar earlier studies for some Rifan basins (El Garouani et al., 2009; Tribak et al., 2009; Sadiki, Bouhlassa, Aujjar, Faleh, Macaire, 2004; Naimi, Tayaa & Ouzizi, 2004; El Aroussi et al., 2011), as well as satellite imagery and the field observations. The values assigned to the different modes of land use is between 0.08 and 0.55 The P factor varies from 1 for non-conservation areas to 0.1 for heavily managed land (Roose, 1996). Due to the lack of regional planning in the study area, the value of 1 was assigned to all basins. After determining all the necessary parameters, the estimation and the mapping of the soil losses are carried out using the RUSLE model integrated into Idrisi Andes software (Lewis et al., 2007; El Garouani et al., 2009; Tribak et al., 2009; Tribak et al., 2017; Abahrour, 2009; Arari et al., 2019). In addition, the dynamics of infiltration and runoff according to soil surface conditions was tested by using rainfall simulation on micro-plots (1m2) using a mini-simulator with rainy ramp with simulated rains of 50 mm and intensities of 80 mm / h (Abahrour, 2009; Abahrour, 2015; Sabir, Roose, Ouagga, Bensalah & Dore, 2007). Before each simulation, the surface condition of the parcels concerned is checked. It is a question of raising the rate of closed surfaces (pellicle and crust of crushing, packed surfaces and pebbles included in the mass of the ground) and of open surfaces (cracks) and covered surfaces (weeds, litter and pebbles) according to the quadrats points method (Roose, 1996; Sabir et al., 2007, Abahrour, 2009; Morsli, Habi, Mazour, Hamoudi & Halitim 2012). Likewise, the initial humidity was tested on samples taken before and after the simulation in the surface horizons of each plot. The simulation tests are spread over different periods of the agricultural year in order to test the evolution of the surface conditions and the preliminary humidity of the soil in the different seasons. It involved cultivated plots as well as fallow or totally abandoned plots. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 164 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 3. RESULTS AND DISCUSSION The aggressive nature of the exceptional rains and their pronounced concentration during short periods of the year create imbalances manifested in excess of humidity, with all the implications that they imply in the dynamics of the environments. They intervene directly in the mechanisms of erosion and flooding and influence the effect of water aggressiveness at the watercourse level. The impact of these phenomena on environments is all the more important as the majority of slopes are bare and subject to strong human influence. These mountains are an old demographic home where the components of the physical environment have undergone significant changes, of which man bears a large share of responsibility. Similarly, the accelerated and uncontrolled human occupation of the urban peripheries, located downstream of the basins, increases the vulnerability of these environments to the hydrological hazards that threaten several peripheral sites in the city of Taza. 3.1. Climate aggressiveness: a source of risk Despite the recurring droughts that characterized the last decades, some years remain largely wet with occasional torrential rains that discharge large amounts of water in short periods. These exceptional events are related to weather situations due to oceanic disturbances or only to localized thermo-convection storms. The study of the annual rainfall evolution since 1970 to 2016, for the two stations of Taza and Had Msila, shows the very irregular nature (specific to the Mediterranean climate) of the rainfall in this Prerifan region. The periods of drought are more homogeneous and are marked by an almost uninterrupted succession of deficit years (from 1980 to 1994). The wet periods are often interspersed with dry years that can sometimes be very severe (this is the case for 1998 and 2007). However, the last phase of the series is clearly marked by records that show a real increase in the cumulative rainfall of the years 1996, 1997, 2003, 2009 and 2010 (figures 2a-2b-3a-3b). The statistical study of daily rainfall recorded at the Taza and Had Msila stations during this period shows that the region is subject sometimes to maximum daily heights exceeding the 100 mm threshold, which are often the origin of hydrological dynamics with particular destructive power. These extreme phenomena are assimilated in some cases, but with a smaller magnitude, to heavy precipitation events (HPE) which affect frequently the western Mediterranean basin and which are part of the major natural risks causing serious consequences for environments and populations (Romero, Doswell III, Ramis, 2000; Argence, 2008; Sauvage, 2019). These daily extremes can reach very significant morphogenetic records. Very demonstrative examples can be cited: 101 mm on 30 January 1987 in Had Msila (33.3% of the monthly module) and 113 mm in Taza on March 14, 2004 (61.7% of the monthly module). Besides, these maximum daily rains, considered crucial for the dynamics of surfaces, field observations have shown us that rains of lower but successive heights can also generate erosive processes and large-scale floods. Very significant records can be achieved in consecutive days. In the Had Msila station, 156 mm were recorded in only 2 days, from 21 to 22 December 1981; this quantity constitutes 50% of the monthly module which was 313 mm. The same station received 175 mm in 3 days in January 1987 and 157 mm in January 1996 (Tribak, 2006). Similarly, the Taza station recorded 168 mm in 5 consecutive days in January 1996. High hourly intensities characterize certain rainfall events that produce large runoff coefficients. They are generally very high for short durations, but weaken once the durations become longer. The maximum intensities in 5 minutes reached very high records 82.2 mm/h on 29/01/1986 and 55.5 mm/h on 7/11/1987. Exceptional maximum intensities greater than 100 mm / h correspond to the very severe storms of early autumn; they cause considerable damage, as was the case on 29/09/97 when a maximum intensity of 102 mm / h was recorded (Tribak, 2006). The occurrence of these events, which give very large quantities of water in a few days, or even in a few hours, is related to localized storms of thermo-convective origin or to oceanic disturbances. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 165 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 0 200 400 600 800 1000 1200 1971/1970 1972/1971 1973/1972 1974/1973 1975/1974 1976/1975 1977/1976 1978/1977 1979/1978 1980/1979 1981/1980 1982/1981 1983/1982 1984/1983 1985/1984 1986/1985 1987/1986 1988/1987 1989/1988 1990/1989 1991/1990 1992/1991 1993/1992 1994/1993 1995/1994 1996/1995 1997/1996 1998/1997 1999/1998 2000/1999 2001/2000 2002/2001 2003/2002 2004/2003 2005/2004 2006/2005 2007/2006 2008/2007 2009/2008 2010/2009 2011/2010 2012/2011 2013/2012 2014/2013 2015/2014 2016/2015 Years )mm( noitatipicerP Annual p reci p itation Interannual avera g e Figure 2a. Interannual variability of rainfall (Taza Station 1970-2016). Source: Centre de travaux agricoles - Taza). -60 -40 -20 0 20 40 60 80 100 Average deviations (%) 1971/1970 1972/1971 1973/1972 1974/1973 1975/1974 1976/1975 1977/1976 1978/1977 1979/1978 1980/1979 1981/1980 1982/1981 1983/1982 1984/1983 1985/1984 1986/1985 1987/1986 1988/1987 1989/1988 1990/1989 1991/1990 1992/1991 1993/1992 1994/1993 1995/1994 1996/1995 1997/1996 1998/1997 1999/1998 2000/1999 2001/2000 2002/2001 2003/2002 2004/2003 2005/2004 2006/2005 2007/2006 2008/2007 2009/2008 2010/2009 2011/2010 2012/2011 2013/2012 2014/2013 2015/2014 2016/2015 Years Figure 2b. Annual rainfall: average deviations (Taza Station 1970-2016). Source: Centre de travaux agricoles - Taza). 0 200 400 600 800 1000 1200 1400 1600 1971/1970 1972/1971 1973/1972 1974/1973 1975/1974 1976/1975 1977/1976 1978/1977 1979/1978 1980/1979 1981/1980 1982/1981 1983/1982 1984/1983 1985/1984 1986/1985 1987/1986 1988/1987 1989/1988 1990/1989 1991/1990 1992/1991 1993/1992 1994/1993 1995/1994 1996/1995 1997/1996 1998/1997 1999/1998 2000/1999 2001/2000 2002/2001 2003/2002 2004/2003 2005/2004 2006/2005 2007/2006 2008/2007 2009/2008 2010/2009 2011/2010 2012/2011 2013/2012 2014/2013 2015/2014 2016/2015 Years )mm( noitatipicerP Annual precipitation Interannual average Figure 3a. Interannual variability of rainfall (Station Had M’sila Station 1970-2016. Source: Centre de travaux agricoles - Had M’sila). -60 -40 -20 0 20 40 60 80 100 120 )%( snoitaived egarevA 1971/1970 1972/1971 1973/1972 1974/1973 1975/1974 1976/1975 1977/1976 1978/1977 1979/1978 1980/1979 1981/1980 1982/1981 1983/1982 1984/1983 1985/1984 1986/1985 1987/1986 1988/1987 1989/1988 1990/1989 1991/1990 1992/1991 1993/1992 1994/1993 1995/1994 1996/1995 1997/1996 1998/1997 1999/1998 2000/1999 2001/2000 2002/2001 2003/2002 2004/2003 2005/2004 2006/2005 2007/2006 2008/2007 2009/2008 2010/2009 2011/2010 2012/2011 2013/2012 2014/2013 2015/2014 2016/2015 Years Figure 3b. Annual rainfall:average deviations (Had M’sila Station 1970-2016. Source: Centre de travaux agricoles- Had M’sila). A - Stormy rains of thermo convective origin are fairly frequent in late summer or early autumn; they generate very exceptional rainfall both in quantity and intensity. Important water quantities can fall in just a few hours after long periods of summer drought. Very significant examples were recorded in the prerifain region during the years 1995, 1997, 2000, 2002, 2007, 2008 and 2010. The violent nature of these rains gives them very high potential for flow and erosion, especially when they occur during the dry period. Their impact is decisive on the ablation and transport capacity at the hydrographic network level; they favor very high flow coefficients which cause disastrous floods. The occurrence of these heavy rains during the warmest months suggests a thermo-convective origin during this period when the anticyclonic situations are dominant. Vertical instabilities in the continental and maritime tropical air masses result from the presence of polar air at altitude, in the form of a small southward incursion of cold drops (Janati Idrisi, Mazoz & Smihi, 2017). This gives stormy weather which produce very abundant rains on the mountain areas in Morocco. The stormy episode of September 27, 2000, for example, caused a real disaster in the region. Abrupt and concentrated rains totaling respectively 38 mm and 31.7 mm, in the two prerifan stations de Ain Boukellal and Bab Chhoub in the north of Taza, were discharged on the region between 15 h 45 min and 17 h (DRH-Sebou, 2000; Akdim et al., 2003; Taous et al., 2010). Their occurrence is linked to a stormy activity on the Prerif and the Eastern Middle Atlas which was produced through the combination of geographical and thermodynamic factors (figure 4a-4b). Indeed, warm winds from the Saharan thermal depression in the south, forced to rise on the south-eastern slopes of the Prerif and the Middle Atlas, came into contact (collision) with Mediterranean maritime influences. This mountain stormy weather is supported by a shift of a cold altitude anomaly of the north-east sector from Central Europe. The Abdellatif Tribak / REA N. 40 (2020) 159 - 182 166 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 presence of a small cold drop (-15 °) animate the convection system from which the formation of a ripple that attracted the hot air masses of the South-East and the fresh ones coming from the north-east, over all the eastern Morocco. Vertical contrasts also play a decisive role in a such situation, due to the large thermal differences between the two atmospheric levels 500 and 850 hPa of around 30° c. similarly, the proximity of mountain obstacles remains favorable to the activity of orographic and thermodynamic lifts. Thus, thermal contrasts between the lower and upper strata resulted in abundant precipitation throughout the Prerif and Middle Atlas mountains near Taza. Figure 4a. Convective Thunderstorm Situation (27-09- 2000) geopotential height 500 hPa at 18h UTC. Source: http://www1.wetter3.de/archiv_gfs_dt.html Figure 4b. Convective Thunderstorm Situation (27-09- 2000) geopotential height 850 hPa at 18h UTC. - Source: http://www1.wetter3.de/archiv_gfs_dt.html B - Very rainy daily episodes or in consecutive days related to oceanic disturbances also constitute a source of risks on several levels. Genetically, these exceptional rain events, which persist for a few days, are generally linked to oceanic disturbances that hit northern Morocco in the wet season. The disturbed currents coming from the sectors west - north - west constitute the most frequent systems which cause abundant rains on the North of Morocco. They are generally related to the displacement of the polar front, which takes southern positions during the wet season. Generally at altitude (500 hPa), the jet stream creates wide undulations at the level of the northern hemisphere and consequently, a great cold valley above the Atlantic and Western Europe. The result is a deep and persistent cyclonic situation in the North of the Atlantic, whose flow reaches and largely covers Morocco, causing a very unstable weather and abundant rainfall for a fairly long time. The situation of March 13, 2004 can illustrate this example of a cyclone event. We can clearly see in (figure 5) the existence on the North Atlantic of a depression well dug and wedged between two anticyclonic cells. The juxtaposition of these cells at the level of the Moroccan coasts promotes the spread of the low pressure corridor and its concentration at the level of Morocco and then the liberation of its wet potential on March 14, 2004. This explains the abundance of rains that have fallen on the region from March 13th to 15th: 141 mm at Taza with 113 mm for the day of March 14th; 214 mm in Oujda, 204 mm in Berkane and 116 mm in Nador (Ben Brahim, 2006). These violent and concentrated rains were the source of disastrous floods in the region of Taza and all the East of Morocco. Similarly, the situation of 29-01-87 shows a vast depression on the North Atlantic, which directs towards Morocco flows from W to NW (figure 6). The Azores anticyclone is shifted south of the 35th parallel. The weather in Morocco is very unstable; it is under the influence of a very active disturbance whose cold sector is constituted of humid maritime polar air and the hot sector constituted of maritime tropical air, coming from the Azores anticyclone. Rainfall is very abundant on the West and the North of the country; the two stations of Taza and Had Msila recorded, respectively, from 29 to 31 of January, 159 and 174 mm. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 167 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 Figure 5. Disturbed situations of the West North West sector (13 – 3 - 2004) geopotential height 500 hPa at 6 h UTC. Source: http://www1.wetter3.de/archiv_gfs_dt.html Figure 6. Disturbed situations of the West North West sector (29 – 01 – 1987) geopotential height 500 hPa at 12h UTC. Source: http://www1.wetter3.de/archiv_gfs_dt.htm Moreover, disturbances of the north and north-east sector can also generate abundant rains in consecutive days. The disturbed currents coming from the north result from a wide low-pressure zone over the Mediterranean and Western Europe due to the displacement of the polar air. The strong cyclonic flows that reach Morocco and all of North Africa cause abundant rainfalls that persist a few days (figure 7). Thus, from January 29 to February 9, 1986 the region is subject to abundant rains which totaled 196 mm at Taza and 256 mm at Had Msila over 12 consecutive days. These rains result from a series of disturbances of the N – Ne sector, directed towards Morocco by a wide depression which covers Western Europe, the Mediterranean basin and the Iberian Peninsula. Thus, the situation of 31/01/86 shows that Northern Morocco is subjected to a wide and deep depression, centered on the northwestern edge of the Mediterranean. The Azores anticyclone, centered at NW, narrows as it shifts to the west; another anticyclone centered on the Scandinavian countries limits the depression to the North. This cyclonic depression which allows the passage of the northern air masses, maintains a disturbed and unstable time in Morocco. It is accompanied by heavy rains which gave on January 31, 1986, 41 mm in Taza and 54 mm in Had Msila with a decrease of the temperatures. This situation persists until February 11 with a gradual shift of the depression, sometimes to the East sometimes to the West, causing heavy rains in the north of the country. It is also important to note that disturbed weather in the southwest sector can cause copious rainfall during the winter. Air movements circulating on the Atlantic Ocean, along the Moroccan coast, allow the digging of a cold valley (figure 8). Cyclogenesis is therefore associated with polar air masses in the south (Janati et al., 2017), which allows the establishment of strong disturbances of the south-west sector favoring abundant rainfall which gave 46 mm to Taza for the only day of February 17th, 2010. 3.2. Impacts of human pressure several studies have shown the close link between social dynamics and the environments dynamics in different parts of the Mediterranean basin (Benchetrit, 1973; Desplanques, 1969; Néboit, 1983; Maurer, 1990; Maurer,1991; Maurer,1996; Lyrintzis & Papanastasis, 1995). For these authors, man influences in many ways on the dynamics of environments. Its role is manifested by a progressive alteration of the natural protective vegetation of the slopes and by a land occupation, unsuited to the climate and morphological context data. For Néboit (1983), the current fragility of Mediterranean environments is also a legacy of history, “... Man imprints his mark on the soils and modeling at a historical rate.”. The work of Lyrintzis (1995) on the Psilorite Mountains in Crete shows that the anthropogenic impact on the degradation of these environments dates back to the Neolithic, “... Human activities, particularly pastolarim, farming and hunting, have damaged the en- Abdellatif Tribak / REA N. 40 (2020) 159 - 182 174 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 and the predominance of open areas and the low humidity levels. On the other hand, in winter the values go down to less than 10 mm/h due to the high humidity of the soils as well as the closing of the surfaces with the persistence of the rains. This therefore explains the very high coefficients of runoff during the winter season which can exceed 70% on strongly clay vertisols. However, at the start of autumn they do not exceed 25% at the end of the simulation; plowing which opens the surfaces and reinforces the roughness remains rather favorable to infiltration. Likewise, the evolution of the plant cover, following the saturation of the soil in rainwater, clearly influences the soil’s ability to runoff and erosion processes; the rate of plant cover on the concerned plots is high in the spring, it ranges between 71% and 82.7%. The comparison of these simulation data with field observations shows effectively, that the recently plowed land, unlike other types of land, shows low runoff coefficients in favor of infiltration in case of low or medium rain intensity. However, this relationship is reversed in the case of heavy rain, which can produce dense networks of incisions and mobilize enormous quantities of sediment. These results show that the influence of human activities, through traditional land use systems, is very significant in terms of the nature of the flow infiltration and ablation processes. Plowed soils record low runoff coefficients compared to those of fallow or totally abandoned land. The combined effect of cropping techniques and plant cover on worked soils can significantly reduce runoff and erosion compared to abandoned land. It seems that the frequency and intensity of runoff on the different types of soil are largely explained by the parameters of the surface conditions (roughness, open surfaces, closed surfaces, covered surfaces, etc...). In case of less heavy rain, the high roughness gives the soil a higher infiltration capacity and an availability to remain open longer and a lower susceptibility to runoff and erosion (Morsli et al., 2012). In addition, the abandoned land, where the soil is bare, compacted and structurally degraded, shows a high frequency of runoff throughout the year and therefore, a significant production of sediment. The interpretation of the erosion quantification and simulation tests result shows that the role of human activities and land use patterns is an important factor in the acceleration of erosive phenomena and the excessive production of sediments. The fields intended for annual crops intensely grazed, remain potentially very fragile to erosional processes. The cleared, bare and cultivated land is the site of various erosive processes and records significant rates of land loss. Otherwise, the progressive evolution of uncultivated areas and badlands in the region can be explained by the abandonment of certain sectors, which is a recent phenomenon linked to migratory movements within the region. The significant expansion of uncultivated land, exceeding 34% in the wadi Tleta basin (period 2000-2014) is closely linked to the phenomena of agricultural land abandonment due to the accelerated process of rural depopulation. The lack of basic protection and landscaping work means that the abandoned plots become a favorable place for runoff and gulling. The rapid compaction of abandoned land, in the lack of any tillage favoring infiltration, allows a concentration of runoff leading to the appearance of dense networks of incisions. This structural degradation of the surface, which increases with time, controls largely the nature of the flows and the runoff coefficients become very high. Similarly, land losses, which are occasionally low in relation to the plowed field, have higher annual rates because of the high frequency of runoff throughout the year. Silty-clay regolith, developed on Miocene marls show, in fact, high runoff rates in late summer and early autumn that can exceed 68% with a solid load of 239 g / l at the end of spring, 179 g / l at the end of winter and 275 g / l at beginning of autumn (Tribak, 2000; Abahrour, 2009). This clay regolith is sensitive to the shear forces which tear the soil from the bottom and allow the installation of gullies. The evolution of the gullies and their annual widening, by different morphogenetic process, makes it possible to produce landscapes of badlands which evacuate most of the sediments towards the main collectors. It seems therefore, that the continuous and rational exploitation of the soil don’t present any great erosive risks. But it is mainly bare, abandoned and overgrazed soils that cause the greatest damage when runoff spreads over steep and bare slopes and collects in gullies (Morsli et al., 2012). This is perfectly in line with our field observations, which confirm that the autumn rains, often intense and aggressive falling on bare and degraded soils, allow generating extreme flows and very high land losses. Intense networks of linear incisions appear on bare steep slopes. The floods of this season, generally very violent and of short Abdellatif Tribak / REA N. 40 (2020) 159 - 182 175 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 duration, are very loaded with sediments threatening seriously infrastructures and urban sites downstream of the basin (photo 2). Photo 2. Impacts of the floods that affected the peripheral areas of Taza during the winter of 2010. Source: Cliche, Abahrour, 2010. 3.4. Vulnerability of peri-urban areas to flood risk In addition, the rain events, previously analyzed, favor very high flow coefficients that cause significant floods. During these episodes, the main rivers in the region undergo sudden and catastrophic floods, which constitute a serious threat to infrastructure and peripheral urban neighborhoods. Indeed, for several decades, the agglomeration of Taza, located downstream of the wadi larbâa basin, has undergone a succession of events of large-scale floods which have generated serious disasters for the local populations. Today, this city is living in a spatial dispersion of urbanization and the invasion of sensitive areas, resulting in the growth of amorphous and fragmented urban fabrics, where the risk of flooding is a crucial problem for the actors. The impacts of floods are not distributed evenly, they are very important in densely populated areas, where the stakes are multiple, and less important in sparsely populated areas. Indeed, the uncontrolled spread of the agglomeration during the last decades in the risk zones accentuates its vulnerability to the floods phenomena. Field observations show that the burst, sometimes uncontrolled, of urban space is framed by a number of dynamics that make these phenomena gain in magnitude and intensity. The emergence of new peripheral neighborhoods, occupied by poor social strata resulting from migratory flows, and their extension into risk areas, is an undeniable reality. The surrounding suburban areas of the city of Taza undergo very strong human pressure although their topography is rugged and unfit to support heavy human occupation. The flows of rural exodus, accelerated in drought periods, have contributed significantly to the increase in the vulnerability of the periphery, since most of the new installations were in non-regulatory construction zones and generally exposed to multiples risks. Promotional prices of land at the periphery have prompted the peasants to seek opportunities to settle without taking into account the risks involved. As mentioned above, this urbanization incompatible with environmental conditions has been stimulated during phases of socio-economic and urban crises, where unhealthy housing has spread to the peripheries, corresponding to naturally unstable areas subject to natural hazards (Tribak et al., 2019). Many Abdellatif Tribak / REA N. 40 (2020) 159 - 182 176 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 of these anarchic and unhealthy urban entities are built on the margins of regulation in the absence of a rigorous urban management policy. In other way, land speculation, which develops in moments of various crises, gives rise to spontaneous urbanization and contributes enormously to the proliferation of informal neighborhoods built on fragile lands to the detriment of urban tools (Royaume du Maroc -SDAUT, 1992). As a result, these peripheries constitute a belt of poverty and marginality that reproduces insalubrities and under-equipment at all scales (Tribak et al., 2019). It is mainly home to rural migrants who have not been able to settle in the city’s equipped neighborhoods. Thus, the outlying districts: el Melha, Clouh, Asdour (figure. 10) located on the banks of the wadi Larbâa river and densely occupied by a population of rural origin, are frequently affected by flooding (Taous et al., 2010; Zyane, 2015). Field surveys and archives of the administrative services show that these districts have been submerged in a serious way, respectively during the years 2000 - 2002 - 2007, 2008 and 2010 et 2013 (Agence Urbaine Taza, 2000; Agence Urbaine Taza, 2002; DRH sebou, 2000; Taous et al., 2010; Layan, 2013). Figure 10. Location of non-regulatory neighborhoods in the northern peripheral zoneof Taza-city. Source: Google earth 2016 image / ANCF 2005 - Taza urban plan. According to the testimonies collected in the field, the flood of September 27, 2000 is the most violent suffered by the population of these neighborhoods. The intense rains of this stormy episode (figure 4), were the source of serious floods of wadis Larbâa and Lahdar which dump their contributions in the upper course of the wadi Inaouène not far from the station of Bab Merzouka (located at 16 km from the city of Taza). According to the report of the DRH-Basin of Sebou (2000), the height of the flood, at Bab Chhoub station in the downstream section of wadi Lahdar, had reached 4.3 m around 17h 30 min with a maximum flow rate of 550 m3 / S. As for the total volume of the flood, it was estimated at 4 million m3 (DRH-Sebou, 2000; Akdim et al., 2003; Taous et al., 2010). The violence of the flood was such that the Kasbat Béni Hitem hydrological station located downstream of wadi Larbâa was completely submerged over a height of 3 m. At the Bab Merzouka hydrological station, located upstream of the wadi Inaouène, the flood has reached a maximum height of 7 m, with a maximum flow of 1786 m3 /S and a total estimated volume of 47.4 million m3 (DRH-Sebou, 2000; Akdim et al., 2003; Taous et al., 2010). This flood has caused a real catastrophe in the region. Several rural centers in the wadi Larbâa Valley have been affected (Tleta Traiba, Ain Boukella, Kasbat Beni Hitem). The outlying districts of the city of Taza, located downstream of wadi Larbâa, have been painfully affected (Douar Abdellatif Tribak / REA N. 40 (2020) 159 - 182 177 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 Chlouh, Douar El Malha, Douar asdour) (DRH-Sebou, 2000; Akdim et al., 2003; Taous et al., 2010; Layan, 2013; Zyane, 2015). The simulation of floods in Oued Larbâ, near these districts, shows that the width of wet sections can reach 300m during a 50-year flood (Layan, 2013). The propagation of water could even reach the height 423.46m, corresponding to an overflow of 1.20m in height, on human installations, such is the case of Douar El Melha on the right bank of Oued Larbâa (Layan, 2013). However, during a 100-year flood water covers the entire major bed. The overflow of waters corresponds to a catastrophic hydrological phase during which the width of the wet sections can exceed 350m in certain sectors covering partially all of the Al Malha, Asdour and douar Allal districts and causing human loss and considerable material damage (Layan, 2013). Such was the case of the flood of September 27th, 2000, of which the flow was estimated at the level of the El Melha bridge at 1163 m3 / S (Agence Urbaine Taza, 2000; Agence Urbaine Taza, 2002; DRH-Sebou, 2000; Akdim et al., 2003; Taous et al., 2010; Layan, 2013). This flood has been widely disastrous in terms of the affected population and damaged infrastructure. The official report records 6 deaths, in addition to hospitalizations. The material damage was significant affecting various sectors (crops, livestock, habitat, infrastructure, trade, etc.); they are officially estimated at more than 41 million dirhams (Province Taza, 2000; Taous et al., 2010). In the same way, the removal of the marly slopes of the basin as well as the erosion of the banks and the landslides make it possible, during this type of flood, to produce and to mobilize enormous quantities of sediments which affect the whole peripheral zones of Taza of the located downstream of wadi Larbâa (photo 2). It is important to emphasize that certain anthropogenic elements increase the vulnerability of these environments in the face of the flooding risk. According to testimonies from the local population, the Taza landfill, located in a meander of Oued Larbâa upstream of Douar El Melha, is an essential factor which amplifies the overflows. The multiple wastes mobilized from the landfill, during the exceptional flood of September 27th, 2000, caused the obstruction of El Melha bridge located downstream. This blocked the flow, generating powerful overflowing floods in the neighboring districts. The bridges installed by the local population on the Oued Larbaa channel near the Al Malha and Asdour districts have been undersized and very poorly adapted, obstructing the circulation of water during floods; their obstruction is often aggravated by various wastes carried away by the flood. By their dam effect, these bridges cause an increase in the level of the flow at the time of floods (Akdim et al., 2003; Taous et al., 2010; Layan, 2013)). Embankments composed mainly of construction wastes constitute another form of anthropogenic impact favorable to flooding in this section of Oued Larbaa. They are easily erodable and are incorporated into the water flow, increasing the solid load and consequently the overflow and flooding conditions (Taous et al., 2010). 4. CONCLUSION The close succession of exceptional rainfall events during the last decades constitutes really a source of risk threatening several areas of the northern provinces of Morocco. These rains, violent and concentrated over time, intervene directly in the mechanisms of erosion and floods. They are a determining factor that largely explains the intensity of erosive processes and the enormity of land loss in these environments. They also explain the deadly catastrophes of the “urban flooding” type that Morocco has experienced in recent years. Besides the enumeration of these events and their harmful impacts on Rifan environments, we have also noted the responsibility of human societies as a factor which accelerates the degradation of environments and multiplies the damage caused by natural hazards. Successive societies in the region over the centuries bear, therefore, a great responsibility in the destabilization of the ecosystems and the modification of the components of the physical environment. This human pressure, to which various land use methods are linked, explains to a large extent, the intensity of environmental degradation. It has resulted, on most sides, in very spectacular agrarian conquests. The lack of land, the origins of which are generally historical or demographic, as well as human activities based mainly on cereals and livestock farming have largely contributed to a vast and varied alteration of natural vegetation and consequently to a serious damage of the Abdellatif Tribak / REA N. 40 (2020) 159 - 182 178 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 environment. The current use of space reflects the extent of human influence and agrarian conquest. Land structures, shaken by various historical events, introduce varieties of occupation, almost are incompatible with the conditions of the physical environment. So indiscriminate clearing on steep slopes everywhere in the region and the practice of subsistence farming, that seeks to extract the maximum of food from the soil, it was enough to accelerate runoff and erosion processes. The overexploitation of cleared land, fueled by a rapidly growing population, explains the extension of crops to areas with steep slopes, resulting in the acceleration of runoff coefficients and erosion processes in this fragile environment. Quantitative assessment of water erosion, using RUSLE model, in this Rifain region shows that average soil losses are well above tolerance levels, although they are close to national and regional ablation rates. Sediment production is therefore excessive, threatening soil capital and infrastructures downstream within the wadi Larbâa basin. Large sediment exports are mainly linked to the exceptional flows which characterize the autumn season when optimal runoff conditions are present (abundant and intense rains, bare and compacted soil, crust of beatings, etc.). These runoffs which generate networks of incisions on the abandoned clay soils are at the origin of spectacular degradations which evolve into badlands often marking the landscape for several years. However, the soil defense and restoration policy carried out by the technical development services remains contrary to the choice of the populations and the requirements of a subsistence economy in crisis. The achievements remain very weak and scattered over a few hectares in the region. During this time, the degradation of the Prerifan environments is accentuated and reaches very advanced stages; it requires immediate and large-scale interventions. These must be done in consultation with the local population; otherwise the difficulties of their implementation will be more and more difficult. Likwise, the enormous human and material damage of the floods, during these last decades, also remind us of the extreme fragility of the urban fabric of the peripheries in the face of this new climatic trend. Uncontrolled urbanization, which developed during the 1980s, encroaching on the minor beds of watercourses, increased vulnerability to the flooding hazards. Several anarchic and unhealthy urban entities are built on the margins of regulation, in the absence of a rigorous policy on urban management. Thus, the public authorities must take the necessary measures to implement and apply the provisions and forecasts of urban planning documents. Similarly, any urban planning must pay particular attention to risk areas, particularly in peripheral zones, in order to avoid or at least reduce the damage caused by recurring flood events in the region. Also, considering the risk of flooding as an intrinsic component of this vulnerable territory can actively participate in changing the vision of planners and their partners as to how to take this phenomenon into account in the development process of the territorial construction. Simlarly, in oder to face these problems, it is of great importance for the concerned actors to rethink traditional systems of spatial planning. This requires the implementation of a bold strategy to address the past urban errors, in order to prevent the increase of human settlements in areas at risk. The recommended approach must include the evaluation, prevention, intervention and reconstruction phases in a process of continuous improvement that takes into account past experiences (Tribak et al., 2018). Finally, it should be remembered that the causes of the dysfunctions imposed to cities and the problems they face, are also to be sought out, and in an urgent and priority way, beyond urban perimeters. The development of the poor and deprived countryside, which constitutes the hinterland of urban agglomerations, is more necessary than ever. These fragile and repulsive environments need sustainable development capable of fixing local populations and minimizing migratory movements. Similarly, the development of water resources, which is a determining factor in the stability of these countryside, remains a national priority that any rural development policy must take into account in order to face the serious consequences of any possible environmental crises. Similarly, watershed management and anti-erosion control require the integration of operations within the framework of a global rural development policy in the region, setting the objective of being compatible with physical and socio-economic conditions of this environment. This implies a renovation of the agrarian economy and a change in existing structures. This requires a modernization of the exploitation means and the imperative creation of other sources of income which can facilitate the reconversion of land and provide the local population with subsistence means. These measures would be likely Abdellatif Tribak / REA N. 40 (2020) 159 - 182 179 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 to revalue the rural world, to meet certain expectations of local populations and consequently to reduce the magnitude of the emigration flows towards the surrounding cities. REFERENCES Abahrour, M. (2009). Contribution à l’évaluation quantitative de l’érosion hydrique dans le Prérif Oriental (Cas du bassin versant de l’Oued Teleta). (Thèse de doctorat en Géographie). FLSH Sais – Fès, 291 p. (Texte en Arabe) Abahrour, M., Tribak, A. & El Garouani, A. (2015). Dynamique du ruissellement et de l’érosion sur les terrains labourés du Prerif oriental: cas du bassin de l’Oued Tleta. In Acte du collqoue international: Eau et Climat: Regards croisés Nord/Sud (p. 99-106). Ublication FLSH sais-Fès, 52. ANCF -Agence Nationale de la Conservation Foncière- (2005). Plan Urbain de la ville de Taza. Agence Urbaine de Taza. (2000). Rapport portant sur les inondations survenues à Taza le 27 septembre 2000. Rapport interne, 6p. Agence Urbaine de Taza. (2002).. Rapport analytique de crue de 22 Novembre 2002, 16p. Akdim, B., Laaouane, M., Taous A. & Obda, Kh. (2003). Risques hydrologiques dans la région de Taza, genèse, conséquences et problèmes d’aménagement. GéoMaghreb, 1, 47-60 Arari, KH., Tribak, A., Amhani, Z., Abahrour, M. & El Ommal, M. (2019). L’érosion hydrique dans le prérif oriental: Cartographie et évaluation quantitative (Cas du bassin versant de l’oued Larbaâ-Maroc). In Actes du Colloque International la vulnérabilité des territoires face aux risques hydroclimatiques». Oujda 15 et 16 novembre 2019. Argence, S. (2008). Prévisibilité de précipitations intenses en Méditerranée:impact des conditions initiales et application aux inondations d’Alger de novembre 2001. (Thèse doctorat: Physique de l’Atmosphère). Université Toulouse. Ben Brahim,Y. (2006). Genèse météorologique des inondations de mars 2004 au NE du Maroc oriental. GéoMagreb 3, 47-54 Benchetrit, M. (1973). L’érosion actuelle et ses conséquences sur l’aménagement en Algérie. P. U. F. Benchrifa, A. (1995). Processus de sédentarisation et risque de désertification: impact environnemental de l’évolution récente du nomadisme pastoral dans les hauts-plateaux du Maroc. In Série: Colloques et séminaires, 50, 79 – 97. Pub. FLSH. Rabat. Bonn, F. (1998). La spatialisation des modèles d’érosion des sols à l’aide de la télédétection et des SIG: Possibilités, erreurs et limites. Sécheresse, 9 (3), 185-192. Boudy, P. (1958). Economie forestière nord-africaine: Description forestière du Maroc. Tome 3. París: Ed. La rose. Desplanques, H. (1969). Campagnes ombriennes: Contribution à l’étude des paysages ruraux en Italie centrale. Ed, Armand-Colin 1969 DRH Sebou, 2000. Crue du 27 Septembre 2000 dans la ville de Taza et régions. Rapport El Aroussi, O., Mesrar, L., El Garouani., A., Lahrach, A., Benabidate, L., Akdim, B. & Jabrane, R. (2011). Predicting the potential annual soil loss using the revised universal soil loss equation (RUSLE) in the Wadi el malleh catchment (prerif, morocco). Present Environment and Sustainable Development, 5 (2), 5 – 15. El Garouani, A., Chen, H., Lewis, L.A., Tribak, A., Abahrour, M. (2009). Evaluation du bilan d’érosion et de dépôt des sols au pré-Rif (Maroc) en utilisant le modèle RUSLE, la télédétection et analyse spatiale. Revue Internationale de Géomatique, 19 (3), 303 – 317. https://doi.org/10.3166/geo.19.303-319 Gartet, A. (1994). Morphogénèse et hydrologie dans le bassin-versant de l’oued Lebène (Rif Méridional et Prérif Central et Oriental, Maroc). (Thèse de doctorat en géographie). Université d’Aix Marseille I, Institut de Géographie Aix-en-Provence. Gomer, D. (1992). Écoulement et érosion dans des bassins versants à sols marneux sous climat semi-aride méditerranéen. Eschborn (Allemagne): GTZ-ANRH, 1992. Grovel, R., 1996. La préservation des forêts du Rif centro-occidental: Un enjeu de développement de la montagne rifaine. Revue de Géographie Alpine, 4 (84), 75 – 94. https://doi.org/10.3406/rga.1996.3887 HCP -Haut Commissariat au Plan-, (1982-1994-2004-2014). Recensement général des populations et de l’habitat, Rabat. HCP (Haut Commissariat au Plan), (2004). Aspects démographique et socio-économique de la région de Taza-Al Hoceima – Taouante. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 180 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 HCP -Haut Commissariat au Plan-, (2005). Dynamique urbaine et développement rural au Maroc: Chapitre 1. Transition démographique - Transition urbaine. Heusch, B. (1970). L’érosion dans le Prérif. Une étude quantitative de l’érosion hydrique dans les collines marneuses du Prérif occidental. Thèse. Ann, Rech, Forest, Maroc, 2, 9-176 Imeson, AC. & Verstraten, JM., (1988). Rills on badlands slopes: a physico-chemically controlled phenomenan. CATENA. Supplement 12, 139-150. Janati Idrisi, A., Mazoz, E. & Smihi, W. (2017). Circulation atmosphérique et ressource en eau dans le cadre du changement climatique (cas du bassin de Sebou, Maroc). Publication FLSH, Sais-Fès, 3-29. Jennan, L. (1990). Evolution récente des systèmes socio-économiques et différentiation spatiale du Moyen Atlas. In Actes du colloque, le Maroc: espace et société. Passau 1989, 73-84 Kerbout, M. (1990). Les mutations des campagnes du Moyen Atlas oriental: Le cas de Beni Yazgha et des Marmoucha. Actes du colloque, le Maroc: espace et société. Passau 1989, 49 – 62. Layan, B. ( 2013). Détermination des crues de projet, modélisation hydraulique et gestion du risque d’inondation dans le bassin versant de l’oued Larbaâ. cas de la ville de Taza (Maroc). (Thèse Doctorat, géologie). Leblanc, D. (1979). Etude géologique du Rif externe oriental au Nord de Taza (Maroc). Notes et Mémoires. Rabat: Service Géologique Marocain, n° 281. Lelandais, F. & Fabre G. (1996). Plan d’aménagement anti-érosif du bassin-versant de l’oued Ouergha (Maroc), Risques d’érosion et systèmes d’information géographique. Bull Réseau Erosion 16, 439-443. Lewis, L., Chen, H. & El Garouani, A. (2007). Modeling soil erosion and deposition utilizing remote sensing and GIS in the Tlata river basin, Morocco. European Geosciences Union 2007, Geophysical Research Abstracts, Vol. 9. López-Bermúdez, F. (2003). Evaluación de la erosión hídrica en las áreas receptoras de los embalses de la Cuenca del Segura. Aplicación de la USLE. In: F. López-Bermúdez y J.B. Thornes (Eds.), Estudios sobre Geomorfología del Sur de España (93-99). Murcia: Universidad de Murcia y University of Bristol. Lyrintzis, G. & Papanastasis, V. (1995). Human activities and their impact on land degradation. Psilorites mountain in Grete: A historical perspective. Land degradation and rehabilitation, 6, 79-93. https://doi.org/10.1002/ldr.3400060203 MADREF (Ministère de l’Agriculture, du Développement rural et des Eaux et Forêts), (1994). Plan national d’aménagement des bassins-versants. Rapport de synthèse. Rabat: MADREF. Retrieved from http://www.eauxetforets.gov.ma/pabv. htm#haut. Mathieu, L. (1977). La géomorphologie et la géologie quaternaire comme bases fondamentales pour une juste définition et une cartographie rapide des sols et des milieux. Application dans la province de Taza (Maroc) et dans la cuvette d’Andoppa (Madagascar). (Thèse Doc ing F.S.A.). Gembloux, Belgique. Maurer, G. (1990). Facteurs physiques et aménagement dans la montagne rifaine. Extr. Rev. Fac des lettres. Tetouan. 4ème année: 4, 93-101. Maurer, G. (1991). Les dynamiques agraires dans les montagnes rifaines et telliennes au Maghreb. Bull.Assoc. Géogr. Franç., 4, 267-279. Paris. https://doi.org/10.3406/bagf.1991.1584 Maurer, G. (1996). L’homme et les montagnes atlasiques au Maghreb. Ann. Géog., 587, 47-72. https://doi.org/10.3406/ geo.1996.20726 Merzouk, A., Fenjiro, I. & Laouina, A. (1996). Cartographie de l’évolution des formes d’érosion dans le Rif Occidental (Maroc): étude multidate utilisant un SIG-Bassin versant. Bull Réseau Érosion,16, 444-56. Morscell, J. & Fox, D. (2004). Une méthode de la cartographie du risque érosif: application aux collines de Terrefort laugarais M@ppemonde, 76 (2004.4). Retrieved from http://mappemonde.mgm.fr/mm4/articles/art04404.html. Morsli, B., Mazour, M., Mededjel, N., Hamoudi, A. & Roose, E. (2004) Influence de l’utilisation des terres sur les risques de ruissellement et d’érosion sur les versants semi-arides du nord ouest de l’Algérie. Sécheresse, 15 (2), 96-104. Morsli. B., Habi, M., Mazour, M., Hamoudi, A. & Halitim, A. (2012). Erosion et ruissellement en montagnes méditerranéennes d’Algérie du Nord: analyse des facteurs conditionnels sous pluies naturelles et artificielles Rev. Mar. Sci. Agron. Vét., 1, 33-40 Naimi, M., Tayaa, M. & Ouzizi, S. (2004). Cartographie des formes d’érosion dans le bassin-versant de Nakhla (Rif occidental, Maroc). Rev, Sécheresse 16, 79-82. Neboit, G.R. (1983). L’homme et l’érosion ASS des publications de la Fac.des Lettres et sci. Humaines de Clermont-ferrand 2 Nouvelle série fasicule 17. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 181 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 Province de Taza. (2000). Les inondations survenues le 27 septembre 2000. Rapport interne 22 p. Rango, A. & Arnoldus, H.M.J. (1987). Aménagement des bassins versants. Cahiers techniques de la FAO. Renard, K.G., Foster, G.R., Weesies, G.A., McCool, D.K. & Yoder, D.C.(1997). Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation (RUSLE). Agricultural Handbook, nº 703, Washington, D.C. Romero, R., Doswell III, C. A. & Ramis, C. (2000). Mesoscale Numerical Study of Two Cases of Long-Lived Qua- si-Stationary Convective Systems over Eastern Spain. Mon. Wea. Rev., 128 (11), 3731–3751. https://doi.org/10.1175/1520-0493(2001)129<3731:MNSOTC>2.0.CO;2 Roose, E. (1996). Méthodes de mesure des états de surface du sol, de la rugosité et des autres caractéristiques qui peuvent aider au diagnostic de terrain des risques de ruissellement et d’érosion, en particulier sur les versants cultivés de montagne. Réseau Erosion Bulletin, 16, 87-97. Royaume du Maroc. (1992). Schéma Directeur d’Aménagement et d’Urbanisme –Taza. Ministère de l’Intérieur. Royaume du Maroc. (2015). Schéma Directeur d’Aménagement et d’Urbanisme –Taza. Rapport de diagnostique - analyse et évaluation prospective. Ministère de l’Habitat de l’Urbanisme et d’Aménagement du Territoire, Agence Urbaine Taza. Sabir, M., Roose, E., Ouagga, T., Bensalah, N. & Dore, L. (2007). Utilisations des terres et risques de ruissellement et d’érosion dans les montagnes au Maroc. Actes des JSIRAUF. Hanoi, 6-9 novembre 2007. Sadiki, A., Bouhlassa, S., Aujjar, J., Faleh, A. & Macaire, J.(2004). Utilisation d’un SIG pour l’évaluation et la cartographie des risques d’érosion par l’équation universelle des pertes en sols dans le Rif oriental (Maroc): Cas du bassin de l’Oued Boussouab. Bulletin de l’Institut Scientifique de Rabat, 26, 69–79. Sauvage, C. (2019). Prévision couplée océan-atmosphère des épisodes méditerranéens: Impact d’une meilleure prise en compte des débits des fleuves et de l’état de mer. (Thèse doctorat Sciences de l’Univers, de l’Environnement et de l’Espace). Université toulouse. Taous, A., Obda, Kh., Tribak, A., Laouane, M., Akdim, B., Marques Furdada, M. & Julia, R. (2010). Cartographie et zonage de l’aléa d’inondation à Taza (Maroc). Application de la méthode géomorphologique intégrée. Géomaghreb, 6, 1-19. Tribak, A. (2000). L’érosion hydrique en moyenne montagne du Prérif oriental (Maroc). Etude des agents et des processus d’érosion dans une zone de marnes tertiaires. (Thèse Doctorat d’Etat). Tribak, A. (2002). Contraintes du milieu et fragilité d’un espace montagnard marocain: Les montagnes du Prérif oriental. Annales de géographie, 625, 227-245. Paris: Armand colin. https://doi.org/10.3406/geo.2002.1655 Tribak, A. (2006). Impacts des phénomènes pluviométriques exceptionnels sur les milieux montagnards marocains: cas du Prerif oriental. In Actes du XIX colloque de l’association internationale de climatologie «les risques liés au temps et au climat », 526-531. Epernay France, septembre 2006. Tribak, A., El Garouani, A. & Abahrour, M. (2009). Évaluation quantitative de l’érosion hydrique sur les terrains marneux du PréRif oriental (Maroc): Cas du sous-bassin de l’oued Tlata. Sécheresse, 20 (4), 333-337. https://doi.org/10.1684/ sec.2009.0205 Tribak, A., El Garouani, A. & Abahrour, M. (2012). Hydrous erosion in the catchment area of the wadi larbaa (Rif mountains, Morocco): Agents, processes and modeling. Present Environment and Sustainable Development, 6 (2), 7 – 20. Tribak, A., Arari, K., Abahrour, M., El Garouani, A. & Amhani, Z. (2015). Quantitative assessment of the hydric erosion and the deposition in a marly catchment of the eastern Rif (case of wadi Tarmast – Morocco. Annals of Valahia University of Targoviste. Geographical Series Tome 15/2015, 2, 101-24. Tribak, A., Abahrour, M., El Garouani, A., Arari, Kh. & Amhani, Z. (2017). Evaluation quantitative de l’érosion hydrique dans un environnement montagnard méditerranéen: cas de quelques bassins marneux du Prérif oriental (Maroc). In Eau et climat en Afrique du Nord et au Moyen-Orient (101-112). Publication UMR IDDES-Rouen. Tribak, A. & El Amrani, H. (2018). Urban occupancy of areas with flood risk and territorial dynamics: The case of the great Nador agglomerations (Morocco). Revista de Estudios Andaluces, 36, 54-71. http://dx.doi.org/10.12795/rea.2018.i36 Tribak, A., El Amrani, H., Abahrour, M., Zyane, F. Z., Azagouagh, k., En-Nasry, E.H., Benriah, N. & El Yagoubi Roudani, S. (2019). Occupation des sites à risques en zones périurbaines: Causes, modalités et conséquences: Cas des villes de Fès et Taza (Maroc). Geo-Eco-Trop., 43, 2, 249-258. Wengler, L. (1993). Cultures préhistoriques et formations quaternaires du Maroc oriental: relation entre comportements et paléo-environnements au Paléolithiques moyen. (Thèse d’état). Bordeaux I. Wischmeier, W.H. (1976). Use and misuse of the universal soil loss equation. Journal of Soil and Water Conservation, 31 (1), 5-9. Abdellatif Tribak / REA N. 40 (2020) 159 - 182 182 © Editorial Universidad de Sevilla 2020 | Sevilla, España| CC BY-NC-ND 4.0 | e-ISSN: 2340-2776 | doi: https://dx.doi.org/10.12795/rea.2020.i40.09 Wischmeier, W.H. & Smith, D.D. (1978). Predicting rainfall erosion losses - a guide for conservation planning. U.S. Department of Agriculture, Agriculture Handbook, Washington, D.C.: 1-537. Zyane, FZ. (2015). Occupation des zones à risques et dynamique territoriale dans les zones périphériques de la ville de Taza. Mémoire Master Géographie ‘ LAGEA, FLSH Sais –Fès. WEBS https://earthexplorer.usgs.gov – LandSat 8th, October 2017 Image Google earth 2016 / http://www1.wetter3.de/archiv_gfs_dt.html) http://mappemonde.mgm.fr/mm4/articles/art04404.html.