SUSTAINABLE CLOSURE DEVELOPMENT PLANNING AND DESIGN FOR THE MUASSIM LANDFILL

SECTION 5

HYDROLOGY STUDY

5-7 | MUASSIM LANDFILL 2011

SUSTAINABLE CLOSURE DEVELOPMENT PLANNING AND DESIGN FOR THE MUASSIM LANDFILL

5.1 INTRODUCTION

Makkah lies in the arid region, where the average annual rainfall is as low as 60 mm. The historical rainfall data show that the annual rainfall may vary between almost 0 to 285 mm. During the winter months, the weather is very pleasant with mean monthly minimum temperature varying between 19°C and 22°C while the mean monthly maximum varies between 29°C and 32°C. The absolute minimum and maximum temperature in this period may reach 11°C and 40°C, respectively. While in summer months, the mean monthly minimum temperature varies from 25°C to 29°C and the monthly maximum of this period may ranges between 36°C and 37°C. The absolute minimum and maximum temperatures in this season may reach 20°C and 47°C, respectively. The minimum relative humidity values range between 38% and 50% throughout the year, while the maximum values range between 78% and 85%.

5.2 RAINFALL

The climate in Makkah area can be described by considering the various air masses that affect rainfall distribution over the area. The climate is a combination of Mediterranean (cyclonic system), which moves in from the north during winter and monsoonal from the southwest in summer. The Hijaz Escarpment altitude is the major factor controlling the quantity and pattern of rainfall. How these air masses and rainfall patterns influence the Kingdom was discussed and mapped previously (Şen 1983; Alyamani and Şen 1992; Subyani 2004; Nouh 2006).

Due to the different morphological units in the landfill area, which encompassed foothills, and mountains, the climatological stations were combined based on whether its location was related to one of these three morphological units. Average rainfall and temperature data are summarized in Table 5.1. This table shows high variation in mean rainfall between the coastal and mountainous areas. Temperatures in the foothills were only slightly different from those in the coastal area, but differed greatly from the mountains. Assessment of the long-term average annual rainfall depth in the study area from 1970 to 2005 demonstrates that the spatial variation of rainfall is influenced by topography (Figure 5.1 and 5.2). The orographic effect states that annual rainfall increases with elevation. Generally, the eastern part of the wadi catchments received considerably more rainfall with an average of more than 220 mm per year near the Hijaz Escarpment as compared to the lower (western) part of the wadi, which received an average of less than 100 mm per year near the Red Sea coast (Tihamah). Overall, rainfall tended to be more regular in the highlands than the coastal plain. As refer to Figure 5.1, the Makkah area normally receives an average annual rainfall of 100 mm and meanwhile, in term of 24hrs annual rainfall, Makkah area also receives almost the same magnitude of 110mm as shown in Figure 5.2.

Table 5.1: Average rainfall and temperature for the main morphological units in the study

(Subyani, 2009)

Figure 5.1: Map showing the isohyetal lines of annual rainfall (Subyani, 2009)

Figure 5.2: Annual maximum observed of 24-h rainfall (Subyani, 2009)

A number of wadis originated from the foothills drain their seasonal flood water towards the Holy city. The Makkah city expands much faster than the capability of the city municipality to design and construct a complete storm sewer network, and as the new development intercepts the natural flood plain and lead to an increase in stormwater runoff as a result of the increase in the percentage of impervious area. For example, many city streets are flooded during the rainy season due to local catchments runoff and depressions or due to unmanageable flow from the wadis. In this situation, even the occurrences of relatively low rainfall events create drainage problems.

The Intensity, Duration and Frequency (IDF) curves for Jeddah based on Saudi Consulting Services (2003) data are shown in Figure 5.3. The Makkah IDF is not available, however based on the annual rainfall depth, the Jeddah IDF curve could be utilized in the design processes.

Figure 5.3: Intensity, Duration and Frequency curve for Jeddah (After Saudi Consult,

2003)

As refered to Saudi Consult (2003), the curve fitting of the data presented in Figure 5.3 that produces the following correlation for rainfall intensity as a function of storm duration and frequency (R2 = 0.99):

I = [8.37+ 17.14 ln(F)] (D)-0.60

Where,

I is the rainfall intensity (mm/hr),

F is the storm frequency period (years) = 2, 10, 20, 50 or 100 years,

D is the storm duration in hours.

Although the average rainfall is only 60 mm, and the maximum and minimum values ranges up to 280 mm, but the storms are more often characterized by a short period but high intensity storm which may lead to flash floods. The recorded history of the Makkah does not record any sever casualty of the flash flood, until the unprecedented devastating flood that hit the eastern part of the Makkah on 1426 (Subyani et al.2009). For example, during Hajj season, Makkah area, 1426H (22 January 2005), experienced a heavy rain storm that was described as the worst in 20 years. As a result, 29 people were killed, and 17 were wounded. Flood waters swept cars off roads and destroyed bridges, electrical towers, and communications. Flash floods also occurred in some parts of Makkah city in January 2008. Most rainstorms within the Makkah area did not exceed 3 h, and according to rain gauge data, rainfall totals did not exceed 100 mm in this area (Subyani et al.2009). Muassim landfill is being slightly 7 km east off Makkah should receive a little more than the Makkah city’s 100 mm, thus 110 mm per year is a reasonable estimate. Coincidently, the country, Saudi Arabia, is also receiving 112 mm per year on the average. The amount of rainfall for Muassim landfill is based on precipitation data by Subyani (2004) of towns in the area, including Makkah, as shown in Table 5.2. Table 5.3 is another of Subyani (2004) which presents a contoured distribution of yearly precipitation around the area.

Return Period (Years) / Duration / Saudi Consulting Services (2003) / Al-Rashid (1994) / Kattand and Gibb (1984)
2 / Intensity (mm)
10 Min / 9.3 / 12.6 / 11.3
30 Min / 15.7 / 19 / 18.9
1 Hr / 20 / 23.1 / 22.6
3 Hr / 23.5 / 26.6 / 26.2
12 Hr / 27.6 / 30.5 / 28
24 Hr / 29 / 32.1 / 32
5 / 10 Min / 17.9 / 20.4 / 16.4
30 Min / 30.2 / 33.4 / 27.7
1 Hr / 38.6 / 41.6 / 36.4
3 Hr / 45.4 / 48.7 / 43
12 Hr / 53.2 / 56.8 / 46.6
24 Hr / 56 / 59.9 / 53.1
10 / 10 Min / 23.7 / 25.5 / 20
30 Min / 40 / 42.9 / 33.1
1 Hr / 51.1 / 53.9 / 45.1
3 Hr / 59.9 / 63.4 / 53.9
12 Hr / 70.3 / 74.1 / 59
24 Hr / 74 / 78.4 / 67
20 / 10 Min / 29.1 / 30.5 / 23.3
30 Min / 49.1 / 52.1 / 38.9
1 Hr / 62.8 / 65.7 / 53.9
3 Hr / 73.7 / 77.5 / 64.4
12 Hr / 86.5 / 90.8 / 71
24 Hr / 91 / 96.1 / 80.4
50 / 10 Min / 36.2 / 36.8 / 27.7
30 Min / 61 / 63.9 / 45.9
1 Hr / 78 / 81 / 64.8
3 Hr / 91.5 / 95.7 / 77.9
12 Hr / 107.4 / 112.4 / 85.9
24 Hr / 113 / 119 / 97.6
100 / 10 Min / 41.6 / 41.6 / 30.9
30 Min / 70.2 / 72.7 / 51.5
1 Hr / 89.7 / 92.4 / 73.5
3 Hr / 105.3 / 109.4 / 88.5
12 Hr / 123.5 / 128.6 / 97.9
24 Hr / 130 / 136.1 / 110.7

Table 5.2: Intensity, Duration and Frequency data of Jeddah as estimated by different

studies

Table 5.3: Mean annual rainfall around the study area (Subyani, 2004)

Location / Longitude / Latitude / Mean Annual Rainfall (mm)
Adham / 40.91 / 20.48 / 327
Firrain / 40.12 / 21.37 / 192
Wadi Muhrem / 40.33 / 21.27 / 185
Ashafa / 40.36 / 21.07 / 260
Jerinuz / 40.42 / 21.07 / 180
Lith / 40.28 / 20.15 / 90
Ghomaiga / 40.45 / 20.33 / 75
Makkah / 39.83 / 21.427 / 100
Bahrah / 39.7 / 21.43 / 60
Jeddah / 39.18 / 21.568 / 60
Dahya / 40.28 / 21.27 / 165
Shadad / 40.22 / 21.35 / 130
Kur / 40.253 / 21.344 / 131

5-7 | MUASSIM LANDFILL 2011