Integration of GIS and HEC-RAS in Floods Modeling of Martil River (Northern Morocco)
European Scientific Journal April 2018 edition Vol.14
Integration of GIS and HEC-RAS in Floods Modeling of Martil River (Northern Morocco)
Amina Azouagh 0
Rabei El Bardai 0
Ismael. Hilal 0
Jamal. Stitou el Messari 0
0 Faculty of Science, Abdelmalek Essaadi University , Tetouan , Morocco
This work describes the application of Hec-RASas Hydrologic Engineering Center derived River Analysis System model to the establishmentof floodplain maps for Martil river. Modeling with Hec-Ras enables calculation of, among other variables, water levels, depths and flow velocities for the different flow configurations and different cross-sectional zones along Martil River, i. e., from the confluence with the Lakhmiss and Mhajrat rivers to discharge into the Mediterranean Sea. This investigation, therefore, presents flood mapping and classification of risk areas using the Hec-GeoRas and Hec-Ras hydraulic modelling tools integrated into the Arcgis information system. The results indicate that the use of aerial photographsprovidesa good knowledge of the morphology and physical characteristics of the river, which will help decision makers to prevent floodingin the urban area of Tetuan.
Hydraulic modeling; GIS; flood area of Tetuan; Morocco
very complex Alpine tectonics structure, and also for its climate conditions.
Although its winter and summer both manifest tempered temperatures, due to
the proximity to the sea, this area receives torrential rains. As a result;
contrasting climate, sometimes causing inundations, floods and landslides
. Floods are periodical events that appear principally by water
overflowing from the main drainage channels.
The inventory of historical floods is far from complete, but it’s
nevertheless indicative of the existence of extreme events, such as those of
December 1976, February 1979, February 1991, February 1996, January 1997,
February 1998, December 2000, 2005, September 2007, December 2009,
August 2013, and of February 2016
(HCFP, 2001 ; Ben Moussa and al.,
.These events are concentrated between the December and February, a
period known with intense rainfall. Floods are considered the second most
widespread natural risk in the region after landslides. Indeed, the flood of
December 26/2000 is a good example of illustration. The damage was
massive; a score of deaths and considerable material damage was estimated at
several million dirhams. The water completely submerged in Coelma district,
and partially that of M'hannech (where the water height exceeded 2 m). The
bypass road, which had not yet been raised up to day, was submerged for
several kilometers. Thus, resulting in a traffic interruption for 7 hours;
industrial units located on both sides of the watercourse were particularly
affected, inhibiting their activities and as a result, 400 workers lost their jobs.
Traffic on Tamouda, Torreta and Coelma’s bridges was also interrupted for
several hours, which prevented citizens from reaching their homes or work.
Moreover the construction site of the new bridge was flooded.
Tetuan and its coastline are part of the northern Rif (North of
Morocco). The city, with its 380718 inhabitants
is limited to the
North by the rural commune of Malaliyine and to the South by the rural
communes Dar Ben Karriche, Zaitoune and Sahtriyine, to the East by the
urban commune of Martil and rural of Azla and to the West by the rural
community of Seddina.
Forming part of Tetuan province, the study area is located between the
Tamouda Bridge and the Martil river outlet wtha flow South West to the North
East, the stretch of the River crosses the Southern part of the city of Tetuan
Of a torrential nature, the Martil River originates in the massif of
BeniLait, benefits from the contribution of three tributaries; Lakhmis, Chakour and
Mhajrate streams. It drains a watershed of 1200 km². Downstream, the river
crosses the city of Tetuan to reach the Mediterranean through the plain of
Martil. From a geological point of view, the city of Tetuan is located in an
alluvial coastal plain. The mountains are formed by three major units: the
Sebtides, the Ghomarides and the calcareous Dorsal. The two first unitsare
formed by the partly metamorphic paleozoic rock, and the Dorsal is of
secondary and tertiary age.
The Martil River is of about thirty kilometers long and takes its source
atthe Beni-Lait massif near the town of Chefchaouen. It crosses the city of
Tetuan before entering the Mediterranean Sea. Usually calm, the Martil River
shows episodically high and very rapid floods during intense rains (Figures 2
and 3). During these periods, the city of Tetuan is often flooded in several
The province of Tetuan is generally characterized by two distinct
seasons: rainy and wet from October to April and then clearly dry from May
to September. This provinceis therefore classified among Mediterranean
regions with diverse climate
The major part of the province records an annual rainfall exceeding
650 mm on average, except in The Eastern part of thewatershed where an
average of 460 mm was recorded at the Oued Laou station.
At low altitude, the average temperatures result in a fairly mild climate,
with very hot periods during July and August (28.3°C to 32.9°C) and very cold
periods during January and February (5.3°C to 8.6°C) . The importance of
precipitation, the impermeability of the land cover and the mountainous nature
of the region make the runoff relatively serious With an important
accumulation up tohydrographic network 540 Mm3/year. However, the
hydrological regime is characterized by a high degree of variability closely
related to the amount of precipitationwheremaximum contributions are
recorded between December and February
(ABHL, 2014 ; Stitou El Messari,
Materials and methods
This investigation was initiated by collecting cartographic and
bibliographic data and measurements available for the study area. This phase
was decisive in the choice of the use of the Hec-Ras model.Therefore, based
on the quality of summaries of previous studies of the assembled data, the
complexity of theoretical calculations based on many equations and the
absence of empirical methods, we opted for the Digital elevation model
(Shahzad and al., 2016 ; Azouagh and al., 2017)
. As a result, we
obtained figures on the magnitude of the considered floods and their spatial
The available DEMs from the 30, 12 or 10 m resolution (NASA)
satellite data did not satisfy the needs for study. These DEMs offer major
variations in relief, while the problem of flooding related to our region requires
more precision. For this reason, we used a set of points resulting from the
photogrammetric restitution of stereoscopic aerial photographs with a
resolution of two meters for the elaboration of our digital elevation model.
This DEM has been used to delineate the watershed boundary, to
define the boundaries of sub watersheds and the hydrographic network. The
DEM also allowed us to analyze the drainage profiles of the land. The river
and floodplain geometry was obtained from aerial photographs. Google
Earth's color images were used to classify land uses to estimate the Manning
(n) values that Hec-Ras needed to run hydraulic calculations. The TIN of study
area is presented in the (Figure 4).
The hydro-meteorological data used in this study were obtained from
the Loukkous Hydraulic Basin Agency of the City of Tetouan. Data on
maximum flow discharge rates were available from 1970 to 2013.We used the
discharge data recorded on 3 stations: Amzal, Ben Karrich and Torreta. Amzal
and Ben Karrich are located on two tributaries of Martil, Chekkour and
Mhajrat River. The Torreta records the flows of the river on the lower part of
the upstream. Records show that peak flows are observed in December and
January over the entire recorded period. The Amzal station records maximums
of 69 m3 /s and 70 m3 /s, the Ben Karrich station records 70 m3 /s and 80 m3/s,
and the Torreta station records 177 m3/s and 152 m3/s in December and
January respectively. On the available series, we noted that the highest flows
were observed during the 1990s and 2000s.
All this work, of uneven quality, already carried out or in progress has
provided essential information on the flood hazard and its global stakes. The
govermentspends huge amounts of money in structural protections. In the
framework of this purely scientific work, and taking in account the available
technologies, our research team have turned to models and softwares which
are known for their effectiveness in the field of hydrological modeling. We
propose a method based on hydrological and hydraulic forecasting platforms
in which the Hec-Rasis intergrated for modeling. The advantage of
"HECRAS" is its compatibility with the Arc GIS and Google Earth.
This software which offers a wide variety of options for modeling
hydraulic systems has been successfully used in comparable areas of medium
mountains and has been the subject of several international publications and
(Gary and al., 2010 ; Iosub and al., 2016)
. The Hec-Ras hydraulic
model is a simplified way to model a river flow. It allows evaluating the flows
and the heights of water on all the sections of a river under different regimes
(permanent and non-permanent, subcritical and supercritical flow). The
HecRas model can also include all hydraulic structures including bridges,
pumping systems, dams, etc. Our hydraulic model developed by using the
Hec-Ras software integrates the entire major bed and the hydrographic
network between the confluence of Lakhmis river and Lamhajrat river.
The modeling implemented is of type "1D". The minor bed bridges,
the major bed dams were also modeled. This modeling presents an analysis
and a synthetic mapping of the hydraulic operation of the perimeter of study
as well as the results of the hydraulic modeling of the floods in Martil River.
It is important to note that prior to the technical phase, we conducted a
survey of some ripariansand testimonies that affirmed the existence of major
floods in the region's past, and that the river had undergone profound
alterations over time. Several tributaries have dried up, disappeared or been
transformed into paths or connecting roads between neighbourhoods such as
Kabul Street, which crosses the Taboula Soufla, Tiknia and Safir
neighbourhoods as shown in (Figure 5).
The cartographic production in Morocco was until recently very
limited, the precise information on the real and original state of Martil river
remains incomplete, hence the incomprehension of certain aspects of its
This work combined raindata, hydraulic models and GIS tool.
(Geographic Information System) for assessing flood flows and delineation of
flood-prone areas in urban area of Tetuan.
The choice of the Hec-Rastool seems to be in accordance with the
criteria of the Marti River, which has a unidirectional flow, with low slopes
varying between 10-4 and 10-6 and depths not exceeding 4 meters. The
HecRas software uses 1D saint-venant shallow water equations to link water
heights and discharges. These equations are deduced from the Navier-Stokes
equations through simplifications related to the river model. The application
of the Hec-Ras model for this investigation is based on three fundamental steps
(Ackerman, 2009 ; Leon, 2013)
Step 1: Creating, using the ArcGIS tool, the HecGeoRAS extension,
the Digital elevation model (DEM) and aerial images, the geometrical data of
Martil River with the minor, major river bed and cross-sections.
Hec-GeoRASis used as the main tool in ArcMapwhereas in ArcGIS
environment, we used Hec-GeoRAS functions to digitize various vector
elements that will allow Hec-RAS to generate the flood model and represent
the results. The correct digitization of elements such as bridges, canals or flow
areas is the basis for launching the flood study
(Ackerman, 2009 ; Leon, 2013)
Hec-GeoRAS therefore allows developping the basic cartography that the
territorial elements of the study area will describe). The digitization of these
elements is employed in subsequent phases to perform the potential simulation
The left and right banks
Lines for simulation
Step2: Apply permanent flow modeling with the Hec-RAS 4.1.0
model, which generates an export file for ArcGIS. Hec-Ras, a software
independent of ArcMap but complementary to the analysis processes.
The calculation of hydraulic profiles along the bed of the studied
section is fundamental for estimating water levels during exceptional flood
events. The levels of river overflow and areas submerged by water will also
be known (Figure 7).These profiles will also determine the drainage areas and
those requiring maintenance.
Step3: Generating the results of water stain: flood surfaces and depth
Hec-Ras Modeling made it possible to compute the different flow
configurations for the cross-sections along the studied section. Water levels,
depths, flow velocities and other variables were simulated. The aerial images
used are of a resolution of 15cm. The banks, vegetation, obstacles and
structures are well identified, which allowed obtaininga fairly precise
geometry of our river. Therefore, we created the main axis of the channel.
Moreover, and considering the characteristics of the watershed in
terms of geology, geomorphology and vegetation cover, the Manning
coefficients retained ranged between 0.04 and 0.045. Similarly, the river is
characterized by its mixed regime, shallow meanders and weak slopes. The
geometry of the water courses is defined by 146 cross-sections (96 stations)
spread over the 30 km of the studied section (Figure 8).
Result and discussion
For a natural watercourse, the flow rate varies according to weather
conditions over the watershed and other processes (e.g., groundwater flow).
The obtained results Hec-Ras by modeling are exported to the tool
HecGeoRAS4.1.0 which is an extension of Hec-Ras on Arcgis to create the flood
zones for each profile (Figure 9), that is applied to flow of each return period
T10, T20 and T50. We have zoomed in three sections A (Figure 10 ; Figure
11), B (Figure 12; Figure13) and C (Figure 14) where the overflows appear to
The zone A: is located a few kilometers away from the Tamouda Bridge, built
on the RS 608 road. Duringthe flood of December 2000, the water rose from
0.5 to 2 m above and below the Tamouda Bridge for a discharge of 2000 m3/s.
In this area the simulation highlights a large rise (increase) in water level that
has invaded the road. The water extent is 60 m on the left bank and 90 m on
the right bank. Depending on the shape of the river more or less circular, the
water with its high speed deviates tangently and leaves its usual straight line.
The velocity diagram produced by Hec-Ras of the three peak flow
profiles (3000, 6000 and 9000 m3/s) confirms this result. Within the principal
channel, the velocities are about 1.27 m/s and on both sides, the velocity varies
from 1.08 on the right bank and 1.14m/s. Also for water heights, we visualize
some differences between the main canal and the two banks. Floods in this
zone occur whenever the volume of water from the upper parts of the basin
exceeds the capacity of the riverbed, water overflows and flows over the plain.
Due to the low slope of less than 5/1000, the river acts as a large holding tank.
The Zone B: About ten kilometers from zone A, another important overflow
appears on the side of the M'Hannech district zone B. In this part of the canal,
where the terrain is poorly (less) permeable, the canal's watercourse changes
shape and appears narrower with limited vegetation on the banks, thus,
creating the effect of a funnel.
The right bank has a depth of 12 m over an extension of 50m and
becomes deeper when approaching the main channel. The velocities in this
section reach 1.8m/s. In the main canal, the water depth is 20 meters and the
current velocity is 2.21m/s and reaches 1.04 m/s on the left bank.
The zone C: corresponds to the OumKaltoum district. This district is
connected with the river outletvia a drainage channel linked also to the inactive
branch of the river, which during periods of intense rainfall becomes active.
This area is submerged in water every year during these periods.
River flow modeling software is sophisticated and increasingly used in
natural hazard management and mapping by delineating risk areas.
The overall results allowed to locate flood zones, velocities and heights
of water, etc. These results are reliable and are consistent with the morphology
of the field.
The study area has undergone profound restructuring during the last
twenty years in parallel with the development of awareness of the flood issue:
bridges, dams, tunnels, rehabilitation of the riverand its tributaries have been
built, yet it only takes a rainy day for the streets and neighborhoods to be
submerged in water allowing panic to set in again.
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