sábado, 11 de noviembre de 2017

20170324-RELLEU.PANTANO-_PaperID_58_Prevention of flood episodes al Relleu_22a24.03.2017xJFCliment-MASoler-MSalgot_10pags

Prevention of flood episodes at Relleu (Allacant Province, Spain) in the Old Times: Les Magnets Water Heritage.
  • 22 -24 March 2017 - 
  •  Cesme- Izmir- TURKEY
  •  IWA-PPFW 2017.
  1. Jose Francisco  Climent Brotons.
  2. Miguel Salgado de Marcay.
  3. Manuel A. Soler Manuel.
Prevention of Flood Episodes at Relleu (Alacant Province, Spain)
in the Old Times: Les Magenes Water Heritage
J. F. Climent*, M. A. Soler**, M. Salgot ***
* Departamento de Geografia, University of Alacant, Sant Vicent del Raspeig, Alicante, Spain.
(E-mail: josefranciscorelleu@gmail.com)
** Casa de l’Escrivà, Relleu chronicler of the city, Casa del Escriva, Magistrado Soler nº 2, Relleu, 03578-Alacant.
(E-mail: casadelescriva@gmail.com)
*** Soil Science Unit and Water Research Institute (IdRA), University of Barcelona. Joan XXIII s/n. 08028Barcelona, Spain.(E-mail: salgot@ub.ed)

The old village of Relleu was established by the Romans ca. 1st c BC. It was located at the left side
of the Magenes torrent in a place called la Coma (small hill), in the lowlands of a still existing Arab
castle. The settlement was growing at both sides of the watercourse and the cultivated lands were
expanding to inside the bed of the torrent. This forced to stabilize the banks and guarantee the
passage of water during the floods as well as for its abatement. The abatement infrastructures consist
on fringes of terracing and channelling works in the orchards of the area. The flooding episodes
along the centuries affected several of the infrastructures as well as some of the properties of the
inhabitants. Apart, a small dam for flood abatement exist to protect the fields located downstream.
This infrastructure contains a smart waterfall to control the outflow and reduce the necessary size of
the works and an underground tunnel located downstream. It is analysed the transformation of bare
land into a cultivated area and afterwards how the disappearance of the cultures affected the
overflooding when the river crosses Relleu.
Water heritage, flood control, hydraulic design, water culture, heritage usefulness, ancient drainage

The municipality of Relleu is located in the southwest of the Iberian Peninsula (Gil and Olcina,
1999), at the end of the Andalusian System (Betic Range), in the central districts of the Marina
Baixa region, Alacant province, Spain; not far away (19 km) from the Mediterranean sea, Fig. 1.
Relleu is the biggest municipality of the province in size, with an extension of 76 km2.
Figure 1. Relleu, Alacant, Spain. How to reach Relleu from the airport of Alacant.
The study area is surrounded by several mountains, which create a kind of shield against the wind.
The mountains are Cabeçó d’Or (1,209 m high, southern side and west-east direction), la Grana and
Carbonera (west side and south-north parallel direction, 1119 and 969 m high respectively) and the
Real and Aguilar ranges (northern and southwest-northwest; and west-east respectively and around
900 m high). Farthest away in the North, the Aitana mountain (reaches 1558 m and lies west-east)
dominates all the Marina Baixa and is minimizing the northern winds effects.
The morphology described is the reason why a great number of ravines, gullies, streams and wadis
alternating with small hillocks, define a curled and winding profile, with more than 80% of the
territory over 400 m of altitude. The minimum height in the dam were runoff is draining in, is 234
m and the maximum is found at the Penya de l’Home in the Cabeçó d’Or mountain (1138 masl).
The village is located at 430 m in the piedmont of the Aguilar range, in the northerly part of the
municipal area.
From the geological point of view, it is a sedimentary basin, surrounded by elevations typical from
the sub-Betic system in the northern end of this range.
Present characteristics
One of the ravines and glens in the area is called Magenes; and its basin is the subject of this paper.
The Magenes is an affluent at the left side of the Amadorio river, and is located in the southern side
of the Aguilar range, northwards of the Relleu town, which is crossed by the Magenes at the parat
(stopped) de Pavia. Down of this site there is a regulation pond (Barciela, López and Melgarejo,
2013; Fontana, Melgarejo and Zardoya, 2012).
Up from this pond, the basin has a surface of 1.6 km2. Its higher point is 895 masl and the pond is at
412 masl with its weir at 416 masl. As the Figure 2 is showing, the right side is flatter than the left
side. Except for the terraces, the basin has slopes over 40% reaching 80% as a maximum (Marco,
2004). In the upper parts, there are calcareous rocks; in the terraces, almond and olive trees are
planted and a few houses can be found. Pines grow in the non-planted areas. Many terraces appear
all over the studied area (Giménez et al, 2010).
From the hydrological point of view, when leaving the municipality and taking into account the
ravines, the Strahler stream order at the exit of the Magenes is 4 (Figure 2).

Figure 2. Magenes’ catchment (Strahler index 4)
Considering the climatic aspects, the Spanish southeast, including the Magenes basin, is
temperate/subtropical and semiarid (Gil and Olcina, 1999). Temperate because is located 38º
latitude North and subtropical because the area is affected by the anticyclone of the Azores and
semiarid because of the great droughts; and is affected by occasional extreme rainfalls. All the
indicated is favoured by several factors; is located leeward of the general westwards circulation of
the wind (föhn effect), the latitudinal location (the same as the Azores islands and Sahara) and a
pluviometric dissymmetry caused by the change of wind trajectory in relation with the
Mediterranean. The temperatures are mild in winter and hot in the summertime. From time to time
intense arctic cold affects the area and provoke the feared frosts. Heat waves are also relatively
Figure 3. Slope value in the catchment. Figure 4. The pond from the bridge
The basin
The Magenes becomes narrow and crosses under the bridge the CV-778 road near Relleu;
afterwards it passes through a terraced area, which has been acting as a lamination structure,
reaching again a narrow area when crossing the town centre. The stream is passing this centre using
the parat de Pavia flat area (Figure 6) and skipping a bank destroyed several time by floods. The
free stream is followed by a big ditch, which was recently remodelled. It is nowadays a trapezoidal
canal finishing in another bank; there the water enters a tube and finally reaches the old lamination
pond under a bridge.
The lamination pond supplies water to the orchards, which initiate there and continue downstream.
The pond is capable to limit the river flow during the majority of flood episodes, avoiding the
overflowing and destruction of the embankments and terraces built beside the ravine. The
lamination pool, in order to have a maximum capacity of storage, uses also the end of the
embankment (Figure 4) limited by the floor of the riverbed stabilized by the different stone dikes
surfacing there and the lateral banks built by men. In this initial part of the pool, a false tunnel
(alcavo) was built and over it, an outer surface of loose material can be found. In this way, part of
the embankments was sacrificed and converted into a lamination pond, in order to protect the
orchards downstream. It is not known how many times the outer surface was destroyed by the

outflows, but it can be observed that the false tunnel has a somewhat bent trace and shows two
consecutive segments with really different hydraulic sections (Figures 7 and 10). The final solution
of the problems suffered was an invisible six-meter high, sixty-meter width loose material small
dam with an orchard in the coronation. The dimensions are large having considered the size of the
basin, which is acting as a lamination pond (Boada et al., 1997). Downstream, the ravine is confined
between the borders of the successive orchards and follows in this way until the Magenes ravine
reaches the Amadorio river in a place called the “Aljecires”.
Figure 5. Road, orchards and embankment downstream Figure 6. Parat de Pavía
Morphology of the old infrastructures
The last historic infrastructure before the lamination pond is the bank of the parat de Pavia. This is
a plate surface where high amounts of water in the flooding episodes are retained before reaching
the village. During the flooding episodes (Figures 6 and 7) along the centuries, the bank has been
destroyed several times.
The pit of the lamination pond is 40 m long, and its altitude is 416.84 m at its beginning, beside the
bridge (Figure 8 left) and 415.21 in the upper part of the ditch of the Rec Major (Main Canal), that
crosses the earthen dam (Figure 8 centre). The width of the system is between 7 and 8 m, and the
depth is 3 m in the bridge and 5 m from the upper part of the Rec Major. At the end, the structure
reaches 6.5 m since there is not an exit or water jump in the bottom and the dam has an earthen
elevation forming the first platform of the new orchard. The start of the drainage gallery was
slightly moved downwards in order to use a step, which was an innovation to improve hydraulic
performance and to save volume for the building of the lamination pond (Figure 8 right). This
building design allows starting the gallery at a lower depth, and gain hydraulic loading at its
beginning, which at the same time permits greater discharges: the admissible ones downwards the
river. This higher flow allows a reduction in the capacity of the lamination pond (Boada et al.,
1997) which is the cause of having a higher return period when laminating the floods of the
Once the water flood fills the lamination pond (around 1,000 m3) the water can spill and the orchard
(around 3,800 m3) starts to be flooded. At this point there are the remnants of a former earthen dam
(1 m high) nowadays nearly disappeared, which used to increase the lamination capacity inside the

Figure 7. Layout and details of the lamination system
The tunnel (Figure 7) starts in the lower side of the pond after the big step (Figure 8 right). The
tunnel has a length of 60 m and a 2 m drop between the entrance and the exit. The section is nearly
rectangular and the basis width is among 1.7 and 2.4 m. The height of the sidewalls is also among
1.7 and 2.4 m with the upper structure in form of a flat arch reaching a height up to the gable
between 2.2 and 2.4 m. It is built partly with masonry and in part is excavated, with an uneven

bottom, because it is the bed of the ravine. The vault is made directly with not-carved stones, which
were setting up the ceiling; remnants of the formwork made of hurdle or thatch still appear. Over it,
lime mortar was placed and over the mortar, carved stones were placed. Once this structure
finished, the structure was overfilled with waste material in order to build the overlying orchard.
The section of the false tunnel is diminishing from the entrance to the exit and is forming a unique
meander nearly straight. The section is estimated to be of around 5 m2.
Figure 8. A flood passing the parat de Pavía
Figure 9. The pond from (left) the bridge (centre) tunnel (right) final fall
Figure 10. Two sections of the tunnel and the wall’s surface
The floods

Although short in time, the Mediterranean rainstorms generate important floods, which can cause
important damages. The regional water authority, the Confederación Hidrográfica del Júcar (CHJ,
2013) evaluated the flow rate of the episodes of the Magenes in the lamination pond to be 21 m3/s
for a return period of 100 years and 37 m3/s for a return period of 500 years. The remnants are
showing that the infrastructures were regularly damaged and ancient people were capable of
modifying the existing works by improving their robustness against the floods fixing or rebuilding
them. In the bank of the parat de Pavía, the changes in the vertical or horizontal alignments of the
dry stone walls after a reconstruction are clearly seen (Figures 6 and 8). Some floods during the 20th
century (Olcina, 1994) caused damages but the most important one was in 1971. The damages were
calculated by the Spanish Ministry of Agriculture to be 167,000 € (translated into euro from the
value of pesetas in 1971). The damages resulting from of the episode were landsliding (10%),
distribution of water for irrigation (5%) and caused destruction in rural roads. During 3 days (5 to 7)
of October 200mm of rain were registered. It is to note that 100mm of rain per square meter in a
single day is the necessary quantity of rain to fill the lamination pond, considering an intensity of at
least 1 mm per minute. In these circumstances, the western part of the municipality just at the
bottom of the parat de Pavia was affected because there the bottom of the ravine has not been
Pluviometry of the basin
Data on pluviometry of the area have been found in the neighbouring meteorological stations of
Relleu, Torremanzanas and Sella (Soler, 2013). The closest one in terms of distance and altimetry is
Relleu; for this reason the main amount of data are obtained from this station. Data have been
obtained also from the webpage of the CEAMED (Soler, 2013) and amateurs from the village. The
data obtained allowed the identification of the most intense periods of rain between 2007 and 2009.
An episode of heavy rain was observed during May 2008 and during the period September –
November 2008 rain was continuous. The greater the height of the meteorological stations the
higher the amount of rain. The highest station is Torremanzanas and the most intense rain was
observed at Sella station (Figure 11). From this figure, it can be commented that in wintertime 2007
and up to March 26th, persistent rain episodes were registered. From May 30th to April 3rd, rain
stopped and afterwards continued up to May 4th. During this time, 274.4 l/m2 were registered. The
next raining period was from September 13th 2007 to October 25th with 378.3 l/m2. From November
22nd to 30th, 71.2 l/m2 were registered. From December 8th until 27th, 110.6 l/m2 were added to the
count. From May 8th 2008, a new period of rain started with the maximum intensities observed and
analysed during the 3 years considered (2007 to 2009). The intensities reached 131.3 and 129.3
l/m2·hour. The accumulation from May 8th to June 3rd was of 467.2 l/m2. From September 10th to
29th 123.5 l/m2 were accumulated. Intermittent rains during October until the 4th of November
added 169.9 l/m2. During 2009, 237 l/m2 were registered during the summertime and 177 during
Figure 11. Rainfalls in the stations of Relleu, Torremanzanas and Sella.
Flood discharges
The perimeter of the basin is 6.1 km and the area is 1.6 km2. The length of the main channel is 2.3

km with a maximum height of 895 m to the Parat de Pavia’s 420 m. The average slope is 20%. The
Gravelius index (coefficient of compactness) is 1.36 with a form factor of 0.30. When applying the
Modified Rational Method the concentration time of the basin is Tc = 0.79 hours, with a uniformity
coefficient of 1.94 and the reduction one being 0.98 per ARF area. Then, a yearly maximum daily
precipitation (Pm) was 65 mm with a variation coefficient Cv of 0.51. An amplification factor of Kt
of 3,799 and a reduction coefficient KA of 0.9863, allows to determine the maximum real daily
precipitation (PD = KA * PD) and a precipitation intensity as indicated in Table 1 (MAGRAMA,
2011; Ministerio de Fomento, 1999).
Table 1. Intensity of precipitation (rainfall) pag8d10
It could be indicated that there are occasions where the soil has reached saturation after several
rainy days, and with additional rain, the runoff coefficient becomes higher. Table 2 has been
prepared using different runoff coefficients applied to several return periods. The theoretical
coefficients used were 0.7; 0.75; 0.8; 0.85: 0.90 and 0.95.
Table 2. Calculated floods using the basic equation indicated (figures in m3·second)
Return periods Return periods (Maxplugin) pga8d10

Note: It is to point out that the results are usually higher than the indicated by the CHJ
Tunnel hydraulic capacity
In order to determine the hydraulic capacity, the hydraulic radius and the roughness of the near
rectangular section of the false tunnel (alcavo) must be known. The total length is divided into two
parts: the first one is of 40 m with the walls quite fully eroded or perhaps not lined, with a high
roughness coefficient (k = 0.10 m); being this section the one with the great wetted surface (Smax)
but with the usual variations of an old structure with sediments in the interior. The second part, 20
m, has a minor section (Smin) but the lining is nearly complete and then the roughness coefficient is
lower (k = 0.01 m). For the calculation of the head loss, the Karman-Prandtl formula (Comolet and
Bonnin, 1973) was used for every part. In this way, the flow-head loss characteristic curve of every
section and the addition corresponding to the entire false tunnel is calculated (Figure 11).
The Figure 11 represents also the three different significant loads in the hydraulic operation of the
alcavo output. The first one corresponds to the head when water in the lamination pond reaches the

coronation of the big irrigation canal, 5 m height over the tunnel. The second one reaches the higher
point of the crest or platform of the orchard, around 6 m. The third load is considered the slope of
the tunnel, which will supply an additional meter with a final head of 7 m. The discharge flow will
be around 36, 42 or 45 m3/sec; allowing the safe passage of water, up to a return period of 100 years
without overflowing the lamination pond.
Figure 11. Hydraulic characteristics of the lamination system
The lamination pond has a capacity of 978 m3 but if the water reaches the overflow level (6 m) the
capacity is a little bit more than 1000 m3. If this capacity is exceeded, the platform of the orchard is
flooded. Those places are usually called “parats” (stopped) because its plat and big surface form is
retaining part of the flood just by inundating the area. In this case, the surface is around 3,500 m2
and at its edge remnants of an earthen speck of a maximum height of 0.80 m, discounting the
infiltration, offers an additional storage capacity of around 2,800 m3 with a gross total of around
3,800 m3.
With respect to the lamination pond, and supposing a linear increase of the flows from 0.3 to 60
m3/s when achieving the Tc (Time of concentration) is 0.76 h, the water level in the pond reaches
the level of the entrance of the tunnel. Then the 3 m step at the falling place is full, and the outflow
is 30 m3/s (at the falling place, Fig.-9 right). It is to highlight that 30 m3/s is the flow after 40
minutes of the beginning of the flooding episode meaning that the real lamination pond has not yet
started to be filled. Those 30 m3 are enough to manage most of the rain episodes, because only a
few flooding episodes can reach this level, but the ones of the return period of 500 years. When the
pit is filled and the excess or accumulated water reaches the level of the canal of the Rec Major, 40
m3/sec are being discharged throughout the tunnel. When the excess water reaches the upper
platform or earthen speck, the outflow of the tunnel will be 50 m3/sec, which is the upper limit of
water transportation in the tunnel and the flowrate reaching the site after 65 minutes of rain.
Nevertheless, the 1000 m3 of the pond should have been filled previously with the excess water
The lamination pond and the tunnel are limiting the expected floods within a return period of 100
years and part of the expected within a return period of 500 years (maximum of 60 m3/sec).
Conclusion: past and possible future risks
The only historical troubling data known have always been upstream of the parat de Pavia and not

downstream of the lamination pond. From this, the usefulness of maintaining the ancient system can
be deduced. This is even more important when in the basin of the Magenes an increase of runoff
and high water flows can be expected in the future, caused by the abandonment of the cultivated
The most important heritage infrastructures are the lamination pond, the step and the false tunnel,
which can be visited and are still in good condition, offering a good service from the point of view
of flooding management. Nevertheless, the most important heritage from the technical point of view
is the step allowing the tunnel to start having water at a higher depth and in this way there is a
greater capacity for discharging water from the very beginning of the flood. In this way, the
lamination by retention of water is delayed because from the very beginning of the episode nearly a
50% of the flow can be disposed of.
In this way, a smaller pond can be used for an effective lamination. The part of the lamination
system consisting of the big floodable area of the orchard loosed the earthen speck and is no more
considered as heritage because has to be rebuilt after every flooding episode which reaches the
orchard. The lamination pond and the tunnel can be following their duties and be improved from the
heritage and touristic point of view if they are well maintained, an easy and safe way of accessing
the sites is prepared, and information panels are installed. Then, the heritage knowledge will
improve and be safeguarded for future generations. At the same time the facilities will be
laminating floods for years.

 (i) Barciela C., López M. I. and Melgarejo, J. 2013 Los bienes culturales y su aportación al desarrollo sostenible  (The cultural heritage and its contribution to sustainable development ). Publicacions de la Universitat d’Alacant,  Alacant, Spain.
(ii) Boada M., Campins M., González F., González M., Just J.,; Lorente, J., Martínez, C., Montes C., Ordeig F., Prada
A., Soler M. A., Suris, J., Tobarra E., Varela M. and Villar J. 1997. Soler. M.A. (ed.) Manual de gestión del medio ambiente  (Handbook of environmental management ). Editorial Ariel, Barcelona, Spain.
(iii) Comolet R. and Bonnin J. 1973 Mécanique Expérimentale des Fluides  (Experimental Mechanics of Fluids ). Mason et cie., Paris, France
(iv) Confederación Hidrográfica del Júcar 2013 Informe para la construcción del puente sobre el barranco de les Magenes  (Report for the construction of the bridge over the Magenes Ravine ). Valencia, Spain
(v) Fontana G.I., Melgarejo J. and Zardoya M.V. 2012 Patrimonio hidráulico industrial, arquitectónico y urbano en el medio ambiente  (Industrial, architectural and urban hydraulic heritage in the environment ) Hispano Cubano,
Colección Storia, Economia, Territorio. Bologna, Italy.
(vi) Gil A. and Olcina, J. 1999 Climatología General (General climatology) . Editorial Ariel.Barcelona, Spain
(vii) Giménez P., Marco J.A., Padilla A., and Sánchez A. 2010 Biogeografía, una ciencia para la conservación del medio (Biogeography: a science for the environment conservation).  Proceedings of the VI Congreso Español de Biogeografía, Alicante 2010.
(viii) MAGRAMA, Junio 2011. Confederación Hidrográfica del Júcar. Plan director de defensa contra las avenidas en la Comarca de la Marina Baja (Alicante ) (Managing plan for the defence against floods in the Marina Baixa county, Alicante ). Apéndice 5 Estudio Pluviométrico. Madrid, Spain.
(ix) Marco J.A. 2004 Atles fotonímic d’Alacant (Alacant photonimic atlas).  Publicacions Universitat d’Alacant. Alacant, Spain.
(x) Ministerio de Fomento. 1999 Programa MAXPLUGIN Programme . CEDEX, Madrid, Spain.
(xi) Olcina, J. 1994 Tormentas y granizadas en tierras alicantinas (Storms and hailstorms in Alicante lands).
 Publicacions Universitat d’Alacant, Alacant, Spain.
Soler, M. A. 2013 Informe: Causas del anegamiento de terrazas o bancales en Relleu  (Causes of the flooding of terrasses in Relleu ). Relleu, Alacant, Spain.
Electronic resources
 (xii) http://cartoweb.cma.gva.es/visor/  (accessed 12 February 2016)
(xiii) http://terrasit.gva.es/  (accessed 15 February 2016)
(xiv) http://www.icv.gva.es/  (accessed 20 February 2016)
(xv) http://www.ign.es/iberpix2/visor/  (accesed 20 February 2016)


AURORA ass. Relleu. The hydraulic mills in the upper Amadorio.  October 2016
20171015-RELLEU-PANTNO-_Mills Amadorio Auroraq 2016_x Manuel.A.Soler Manuel_5pags

10170324-RELLEU.PANTÀ-_PaperID_58_Prevention of flood episodes al Relleu_22a24.03.2017xJFCliment-MASoler-MSalgot_10pags.


20171106-RELLEU- a VALENCIA en el salón de actos del * Colegio de Ingenieros de Caminos, Canales y Puertos de la Comunidad Valenciana*-

20171106-RELLEU- a VALENCIA en el salón de actos del * Colegio de Ingenieros de Caminos, Canales y Puertos de la Comunidad Valenciana*-

20170507-BIC Pantano de Relleu Colegio de Ingenieros de Caminos, Canales y Puertos de Alicante - Mayo 2017 x Manolo Soler.


20171106-RELLEU-PRESA :.- a VALENCIA en el salón de actos del * Colegio de Ingenieros de Caminos, Canales y Puertos de la Comunidad Valenciana*-  https://relleupantano.blogspot.com.es/2017/11/20171106-relleu-valencia-en-el-salon-de.html 


No hay comentarios:

Publicar un comentario