International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 321–332, Article ID: IJCIET_10_04_033
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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EFFECT OF ROAD’S SLOPE ON THE EFFICIENCY
OF THE RAIN STORM DRAINAGE NETWORKS
Gamal M. Abdel-Aal
Prof of hydraulics, Water & Water Str. Engineering Department,
Faculty of Engineering, Zagazig University, Zagazig, Egypt
Maha Rashad Fahmy
Assoc. Prof, Water & Water Str. Eng. Department,
Faculty of Engineering, Zagazig University, Egypt
Ismail Fathy
Dr. Water & Water Str. Engineering Department,
Faculty of Engineering, Zagazig University, Egypt
Amira. A. Fathy
Msc. Water engineering 2009, Ministry of Water Resources and Irrigation,
Sharkia, Egypt
ABSTRACT
The frequent rainfall has increased recently especially in arid region due to global
warming. This phenomenon caused a set of problems such as disruption of traffic and
increasing pollution due to stagnation of water. This paper deals with the
experimental investigation of the storm network drainage system efficiency by
changing longitudinal and side slopes of the roads. The altering of road slopes has
been done through two stages: the first stage, Six side slopes
(1.5%,2%,2.5%,3%,3.5%,4%) are used with constant longitudinal slope 0.3% and the
second stage, five longitudinal slopes (0.3%,0.4%,0.5%,0.6%, 0.7%), are used with
constant value of side slope 3%. The results indicated that as the side slope increases
the efficiency of discharge increase, where the efficiency increased by 10% as the side
slope increase from 1.5% to 4%. Also from second stage, the results showed that as
the longitudinal slope increases the efficiency of discharge decrease, where the
efficiency by 5% as the longitudinal slope increase from 0.30% to 0.70%. In addition,
the results specified that Change in the road side slope has a significant impact on
storm drainage efficiency than road longitudinal slope.
Keywords: Hydraulics, Grate, Water Depth, Drainage System, Inlet Efficiency, Longitudinal
Slope Cross Section Slope.
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Gamal M. Abdel-Aal, Maha Rashad Fahmy, Ismail Fathy and Amira. A. Fathy
Cite this Article: Gamal M. Abdel-Aal, Maha Rashad Fahmy, Ismail Fathy and
Amira. A. Fathy, Effect of Road’s Slope on the Efficiency of The Rain Storm
Drainage Networks. International Journal of Civil Engineering and Technology 10(4),
2019, pp. 321–332.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4
1. INTRODUCTION
Good knowledge of the hydraulic behavior of an urban catchment and its surface drainage
system is an essential requirement to guarantee traffic and pedestrian safety, which evade
many problems such as accumulation of water, leading to increase pollution and disruption of
daily life. The hydraulic efficiency of the rainwater drainage systems simultaneously controls
the rate of water removal from the precipice and the amount of water that can be included in
the storm system. Several previous studies have addressed the study of some variables
affecting the efficiency of drainage of rainwater. AASHTO [1], specified a methodology to
estimate the hydraulic performance of grated inlets located in a gutter at the road side. The
set-up had simulated rainfalls which allowed the surface runoff from gutter and carriageway
to approach the grate inlets, similar to actual flow conditions on a road. This differed from
earlier studies where the simulated surface runoff was a continuous steady flow Pezzaniti et
al. (1999) [8]. Guo (2000) [4], presented an investigation on street hydraulic capacity. It was
found that the street storm water capacity at a sump is in fact dictated by the storage capacity
rather than the conveyance capacity. Sipahi, Sabri Özgür (2006) [13], tested the grate
interception capacity at different longitudinal slopes and did not take into account the cross
section slope. The result show that the grate efficiency is affected by the longitudinal slope of
the channel, the discharge efficiency of the grate is higher as the longitudinal slope
approaches to horizontal and the efficiency of the grate increases when the quantity of flow
increases in the channel. Russo(2009)[9], studied experimentally four types of grates, found
typically in Spain and differing in the alignment and distribution of the slots, under different
longitudinal slopes and five approaching flows. They formulated four linear relations, one for
each grate type, which link the hydraulic efficiency to some particular flow conditions
(Froude number and water depth) and the grate length. The efficiency of Portuguese gullies
was numerically studied by Carvalho et al. (2011) [3], using a 2D (Volume of Fluid /
Fractional Area Volume Obstacle Representation) model. Rainfalls of different intensities
were simulated via a network of pipes overhung 1m above the road surface with sprinklers at
2m staggered intervals. Jitendra et al (2013) [5], carried out a framework for quantification
of the effect of drainage quality on structural and functional performance of pavement by
identifying a simple framework for quantification of the effect of drainage quality on
structural as well as functional performance of the pavement. The study was further
extended by Russo et al. (2013)[10] ,with the formulation of empirical expressions to relate
grate hydraulic performance to flow parameters and grate geometry. Magdi, (2014) [6],
studied the impacts of poor drainage on road performance in Khartoum, a city in Sudan with
two case studies; attempts were made to find out the reasons for road failure within the first
five years as a result of poor drainage. In this quest, it was discovered that four basic reasons
lead to early deterioration of road pavements in the study, these factors according to the
research includes, poor drainage design and construction, poor maintenance structure, use of
low-quality materials and no local standard of practice. Muhammad, (2014) [7], studied
highway drainage system and started that highway is importance for removing water from the
road surface, preventing ingress of water into the pavement, passing water across the road,
either under or over and preventing scour and/ or washout of the pavement, shoulder, batter
slopes, water courses and drainage structures. He identified types of drainage on the highway
to include kerb and gullies, surface water channel, combined filter drain (French drain), overhttp://www.iaeme.com/IJCIET/index.asp
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Effect of Road’s Slope On The Efficiency of The Rain Storm Drainage Networks
the-edge drainage, drainage channel locks, combined kerb and drainage units, linear drainage
channels, fin and narrow filter drain (sub-surface drainage) and edge drainage for porous
asphalt. R. Veerappan and J. Le (2016) [11], studied the effect of different type of grates on
the hydraulic efficiencies in terms of flow interception by using a network of overhanging
pipes. The results indicated that the existing grate inlet designs can intercept up to 96% of the
surface run-off and G2000 grate inlets intercepted more flows than G2012 grate inlets. Smith,
2006[14], Schmitt et al. (2004) [12], investigated how surface runoff is delivered to grates
with little regard. The aim of this study is to determine the effect of roads slopes (side and
longitudinal) on the efficiency of storm network drainage system, also to create the
relationship between storm network efficiency and road slopes.
2. DIMENSILAL ANALYSIS
Dimensional analysis based on Buckingham (1914) [2], theory is used to develop a
functional relationship between the efficiency of discharge of grates and the other physics
quantities involved in the phenomenon as shown in figure (1). By applying the Buckingham
theorem, Equation (1) can be written in dimensionless form as:
£=ƒ(Q, Lo , Wo , Hg, Sx , Sy)
(1)
In which: the all parameter as show in fig no (1)
hg : water depth at grates upstream
hu : water depth at flume upstream,
W: the channel width,
Wg: the water spread beside every grate,
g1, g2, g3, g4. g5 g6,: refers to the grate’s 1g, 2g, 3g, 4g. 5g 6g,: refers to the number of
position
grates
L: the length of the flume,
Lg: the distance from each grate’s position,
£: efficiency of discharge = qi/Q.
Q: the total inlet discharge
Sx: Side slope
Sy: longitudinal slope
Hg: relative grate height = hg/hu,
Lo: relative grate distance = Lg/L,
Wo: relative width = Wg/W
Plan
Eleve
Figure 1 Definition sketch for the experimental models.
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3. EXPERIMENTAL WORK
The experimental work was carried out in the hydraulics and water engineering laboratory,
Faculty of Engineering, Zagazig University within the period from December 2018 to
March 2019. The Flume that made from a self-colored, glass reinforced plastic mounding is
used during the experimental tests. The dimension of this flume is 0.63 m width, 0.1m depth
and 6m length. The total discharge is measured using a pre-calibrated orifice meter. The point
gauge was used for measuring the water depths formed in the mobile bed. the different cross
section slopes (1.5, 2, 2.5, 3, 3.5, 4 %) of flume are used as well as different longitudinal
slopes (0, 0.3, 0.4, 0.5, 0.6, 0.7 %). There were six holes with diameter 5 cm at the bottom of
the flume through a distance 5.4 m which far away the edge of flume by 2 cm. The holes are
connected by a pipe with diameter 5 cm through which disposal drain surface water to a large
tank with dimension (1.20m, 0.60m, 0.60m) as shown in figure (2). The number of 45 runs
was done; each run took time 30 minutes to adjust the total inlet discharge. Water surface
level along the flume in two directions and the amount of water which drained from grates are
measured.
Figure (2) The flume of experimental tests
4. ANALYSIS AND DISCUSSION
The experimental work was divided into two stages. The first stage, studied the effect of
changing road side slopes on storm water drainage system efficiency; the relative water depth
and the relative water width. During this stage the side slopes changed through the following
values (1.5%,2%,2.5%,3%,3.5% and 4%) with constant longitudinal slopes 0.30%. The
second stage, investigated the effect of changing road longitudinal slopes on storm water
drainage system efficiency, the relative water depth and the relative water width. Through this
stage the longitudinal slopes changed through the following values (0.3%,0.4%,0.5%,0.6%
and 0.7%) with constant side slope 3%. Two stages done with passing discharge from (1
L/sec to 6 L/sec) and different number of grates (1, 2, 3, and 6 grates) along the flume length.
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4.1. FRIST STAGE
Three different experimental work done through stage. During this stage, the side slope has
been changed with constant longitudinal slope equal 0.30%.
4.1.1. The effect of side slope to drainage efficiency
The effect of increasing side slopes through the following values (1.5%, 2%, 2.5%, 3%, 3.5%,
and 4%) on the drainage efficiency was studied with different passing discharge (1 L/sec to 6
L/sec). Also through experimental work, different number of grates (1,2,3, and 6) along the
channel length are used, (e.g. 1 grate, there is only one grate along the flume length). Figures
(3) and (4) show the relation between the passing discharge (Q) and the efficiency of grates
for different number of grates by using different side slopes (2%, 4%) respectively. The result
indicated that the efficiency was decreased by about (30% to 40%) as passing discharge
increases when the number of grates and side slope are constant. In addition, the increasing of
the side slope from 1.5% to 2% and 4%, the efficiency increased by (2.1%) and (9.3%)
respectively, this means that increased side slope by 100% the drainage efficiency increased
by (7.2%).
Fig. ( 3) relationship between (£) and (Q) for different
no of grates at (Sx= 2% , Sy= 0.3%)
Fig. (4) Relationship between (£) and (Q) for different
no of grates at (Sx= 4% , Sy= 0.3%)
In addition, the effect of changing side slope on efficiency of drainage system was done
for using one grate only, two grates, three grates and six grates along flume length as shown
in figure (5), figure (6), figure (7) and figure (8) respectively. The results indicated that the
efficiency is increased by (26%), (41.5%), (51.5%) and (62.2%) for using one grate, two
grates, three grates and six grates respectively. Moreover, the efficiency is increased by
(40%), (42.1%), (45.1%), (47.1%), (48%) and (49%) for using 1.5%, 2%, 2.5%, 3% 3.5% and
4% side slope respectively.
From the previous discussion, it is obvious that by increasing the side slope of flume, as
well the efficiency of discharge increases for different number of grates, leading to increase
the amount of water over grates and the opportunity for grates to harvested excess water.
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Fig. (5) relationship between (£) and (Q) for using 1 Fig. (6) relationship between (£) and (Q) for using 2 grates
grates with different cross section slopes
with different cross section slopes
Fig. (7) relationship between (£) and (Q) for using 3 Fig. (8) relationship between (£) and (Q) for using 6 grates
grates with different cross section slopes
with different cross section slopes
4.1.2. The effect of side slope on relative water height
The water depth along the flume was measured at upstream each grate to investigate the effect
of increasing the side slopes on water surface profile and redistribution of water along the
flume. Figures (9) and (10) show the relationship between relative grate water height, and
relative grate distance with different side slopes for using six grates at passing discharge (1
L/sec), and (6 L/sec) respectively. Figure (9) indicates that the relative water height at
upstream grate number (g1, g2) are increased as side slope increase and vice versa at the other
grates due to the lack of water for using small discharge. But by using big passing discharge,
the relative water height is increased gradually along the flume by increasing side slopes from
(1.5%) to (4%) within (16%) as shown in figure (10).
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Fig. (9) relationship between relative grate depth and
relative grate length with different cross section slope
(Q=1 L/sec, 6 no of grates)
Fig. (10) relationship between relative grate depth and
relative grate length with different cross section slope
(Q=6.0L/sec, 6no of grates)
4.1.2. The effect of side slope on relative water width
The water spread was observed on the flume with increasing side slope; the water had been
receding in the cross-section direction, indicating the efficiency of the grates in the disposal of
excess water. Figures (11), and (12) show the relationship between relative water width and
relative grates distance for using different side slopes at passing discharge (1.2L/sec), and (3.3
L/sec) with using 6 grates. It can noted that as the side slope increase the water spread width
is decreased by average (26%, 18%) for passing discharge (1.2 and 3.3 L/sec) respectively.
Fig. (11) relationship between relative water spread width Fig. (12) relationship between relative water spread width
and relative grates distance for different cross section slope and relative grates distance for different cross section slope
with 6grates at Q=1.2L/sec
with 6grates at Q=3.3L/sec
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4.2. Second Stage
Also three different experimental work done through this stage. During this stage, the
longitudinal slope has been changed with constant side slope equal 3%.
4.2.1. The effect of longitudinal slope on drainage efficiency
The effect of increasing longitudinal slopes through the following values (0.3%, 0.4%, 0.5%,
0.6%, and 0.7%) on the drainage efficiency was studied with different passing discharge (1
L/sec to 6 L/sec). Also through experimental work, different number of grates (1,2,3, and 6)
along the channel length were used. Figures (13) and (14) show the relationship between the
passing discharge (Q) and the efficiency of grates for different number of grates by using
different longitudinal slopes (0.3%, 0.6%) respectively with constant value of side slope 3%.
The results indicated that the efficiency was decreased by about (26.5 %, 33%) as passing
discharge increase when the number of grates and side slope are constant. In addition,
increasing of the longitudinal slope from 0.3% to 0.7% the drainage efficiency decreased by
(5%).
Fig. (13) Relationship between (£) and( Q ) for different
number of grates by using (Sx= 3% , Sy= 0.3%)
Fig. (14) Relationship between (£) and (Q) for different
number of grates by using (Sx= 3%, Sy= 0.6%)
Comparisons of the experimental results for changing longitudinal slope on efficiency of
drainage system were done for using one only grate, two grates, three grates, and six grates
along flume length as shown in figure (12), figure (13), figure (14), and figure (15)
respectively. It is noted that, the efficiency increased by (24.6%), (40.6%), (51.25%), and
(61.0%) for using one grate, two grates, three grates, and six grates respectively. Moreover,
the efficiency decreased by (47.1%), (45%), (44.1%), (43.41%), and (42.3%) for using 0.3%,
0.4%, 0.5%, 0.6%, and 0.7 longitudinal slope respectively. This can be explained by
increasing the longitudinal slope increase the velocity of the water, so the grate harvesting
decrease which negatively affects the efficiency of discharge.
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Fig. (15) relationship between (£) and( Q ) t for
different slope by using 1 grate
Fig. (16 ) relationship between (£) and( Q) for different
slope by using 2 grates
Fig. (17) relationship between (£) and( Q ) for
different slope by using 3 grates
Fig. (18) relationship between (£) and( Q ) for different
slope by using 6 grates
4.2.1. The effect of longitudinal slope on relative water height
Changing the longitudinal slopes has an effect on the water level as shown in figures (17) and
(18). These figures illustrate the relationship between relative grate water height, and relative
grate distance with different longitudinal slopes for using six grates at Q = (1.6, and 6l/sec)
respectively. It is observed that, average relative grate height decreased as the longitudinal
slope increase for using passing discharge (1.6L/sec) and (6L/sec) by (13%,12%)
respectively.
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Fig. (19) relationship relative grate water depth and Fig. (20) relationship relative grate depth and relative
relative grate length with different longitudinal slope grate length with different longitudinal slope (Q=6.0L/
(Q=1.6L/sec, for 6 grates)
sec, for 6 of grates)
4.2.3. The effect of longitudinal slope on relative water width
The same observations for the effect of changing the longitudinal slope on the water spread
width were investigated. Figures (19), and (20) show the relationship between relative water
spread width relative grate distance for using 6 grates, and different longitudinal slope for
passing discharge 1.2, and 3.3L/sec respectively. The result indicated that the relative spread
with reduction by (5%, 15%).
Fig. (21) relationship between relative water spread width Fig. (22) relationship between relative water spread width
and relative grates distance for different longitudinal and relative grates distance for different longitudinal slope
slope for 6 grates at Q=1.2L/sec
with 6grates at Q=3.3L/sec
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5. CONCLUSIONS
The following conclusions, which are valid within the experimental delimitations, could be
stated as follows:
1. The efficiency of water discharge system increased as the number of grates increase for using
different longitudinal and side slope by average (36%)
2. Increasing the passing discharge from 1L/sec to 6L/sec led to decrease the efficiency of water
discharge for all tests done by average (27%)
3. The efficiency of discharge increase as the side slope increase from 1.5% to 4% slope about
9%.
4. The efficiency of discharge decrease as the longitudinal slope increase from 0.3% to 0.7%
about 5%
5. It also shows that change in side slopes has higher impact to the hydraulic efficiency of grate
inlets than change in longitudinal slopes. When longitudinal slope is adjusted from 0.3% to
0.7%, inlet hydraulic efficiency drops from 47.1% to 42.3%. However, when side slope is
adjusted from 1.5% to 4%, inlet hydraulic efficiency can be increased from 40% to 49.3%.
6. The depth of the water in upstream grates increases with increasing of the passing discharge.
But as the number of grates increased the relative grate height decrease by 12.5%
7. Increasing the side slope from (1.5% to 4%) increased the relative grate height by 6%, at
variance of increasing the longitudinal slope from (0.3% to 0.7%) decreased the relative grate
height by 7.5%.
8. Finally, the relative water width decreases as each of longitudinal and side slope increase.
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