Quantitative Geomorphological and Hydromorphometric Analysis of Drainage Basins of As Sabriyah (Kuwait) Using GIS Techniques

A well-developed drainage network was carved in the study area in a hard calcretized and gypcretized gravelly sand of the Dibdibba Formation (Al-Rukham slope) in pluvial episodes in the post-pleistocene age, and is referred to be paleo-drainage due to the current witnessed aridity. This study aims to investigate the geomorphologic, morphometric, and stratigraphic characteristics of the paleo-drainage system and its role in recharging shallow aquifers. Morphometric analysis was accomplished using GIS and remote sensing techniques. Six vertical pit holes were dug across the area to investigate the stratigraphy and recharging capacity. The drainage system is composed of 10 closely spaced, subparallel, dendritic, elongated, and variant-sloped drainage basins with highest stream order of 5. Water flows NE from Al-Rukham ridge’s crest (60 m a.m.s.l.) downstream in Khor Al-Subiyah coastal flat. The bed rock’s hard resistant nature lowered its infiltration and recharging capacity to the shallow aquifer, whereas the coarse-grained wadi fills deposits increased infiltration capacity of the surface sediments, but the water percolation chance is limited as it eventually directed seaward by the same-directed general topography resulting in limiting potential recharge to the shallow aquifers. This is suggested to oppose the salt water intrusion and thus enhance fresh water quality.


Introduction
The study area (As Sabriyah) is located on the north and the northeastern part of Kuwait adjacent to As Sabbiya area towards the northeast and along the coastal line of Khor As Sabbiya, which separates the area from Bubyan island (Figure 1  the coastal parts to about <60 -65 m heading to the middle inland westward and about 34 -36 m to the west, with geographic coordinates (E47˚47' -48˚00' -48˚04', N29˚42' -29˚53') and it occupies an area of ≈301.056 km 2 . In As Sabriyah area, a well-developed drainage network was carved in a hard calcretized and gypcretized gravelly sand of the Dibdibba Formation. This drainage network is thought to be developed in pluvial episodes in the post-pleistocene age due to the current aridity that the area witnesses, and therefore they are referred to be paleo-drainage network. This study aims to investigate the geomorphologic, morphometric, and stratigraphic characteristics of the Paleo-drainage system in As Sabriyah area in the north and the northeastern part of Kuwait, in order to assess the role of drainage network in recharging of shallow aquifers. The drainage basins were classified and mapped using GIS and remote sensing applications. The study is also aiming to discuss the environmental implications of the A. Al-Hurban et al. Journal of Geographic Information System studied drainage systems in the study area.

Previous Studies
The pattern, density and geometry of a drainage system of any geographic area are controlled by several factors. Such factors include the area's morphology, topography, surface geology, and climatic conditions, particularly the rate and frequency of precipitation which plays a significant role in triggering the drainage pattern and retaining it through the action of the surface runoff on the exposed rocks and sediments [3] [4]. The fluctuation in precipitation and the drought periods will directly affect maintaining the drainage system and indirectly the hydrological system and recharge off the shallow aquifers in an area, especially in arid deserts. Therefore, it is essential to study the geomorphological characteristics of the area in order to reveal their influence on the hydrological and environmental conditions of the present-day arid deserts; and in assessing the catchment of the present-day runoff and recharging of shallow aquifers, as well as, the development of soil material.
Though, the literature on drainage morphology in Kuwait is limited, but the drainage system of Jal Az-Zor escarpment was studied [5], as well as its sedimentomorphology [6]. A detailed morphometric analysis of the drainage basins in Kuwait was conducted, in addition to their genesis, their impact on the present-day arid environmental conditions, and the localities of natural recharge and the potential occurrence of limited shallow phreatic aquifers were estimated [3]. Several investigations on the paleodrainge system in Ar-Raudhatain and Umm Alish areas north of Kuwait were conducted [7] [8].
Generally, Kuwait is characterized by a long, dry, hot and windy summer climate that witnesses remarkable diurnal and monthly variations. Annual mean precipitation range is (23 -45 mm). Monthly mean evapotranspiration range is 67 mm in January to 324 mm in July. Dust and sandstorms characterize Kuwait's weather, where sandstorms frequently occur in summer, the wind prevailing direction is from northwest and wind speed may exceed 5.5 m/s. Kuwait Group is a terrigeneous clastic depositional sequence of Miocene to Pleistocene age, and consists of three formations in the northern part of Kuwait, but barely differentiated in the southern areas (Figure 3(a), Figure 3(b)). These are from bottom to top Ghar, lower Fars and Dibdibba Formations, where Dibdibba is a fluviatile sequence of sands and sandy gravels and covers most of the northern area of Kuwait [1]. This shows that the study area geologically belongs to the upper member of Dibdibba Formations and physiographically, it is located in Al-Dibdibba gravel physiographic province. Journal of Geographic Information System geomorphic zones of Kuwait [10] showing that the study area is located in morphological zone (8) named Al-Ruham slope. The same figure also shows the classified morphostuctural features of Kuwait surface [4], where the study area is surrounded by morphostructural features (3) the northern ridge, (4) Al-Rawdhatain and Um Al-Aish depression and (5) Al Abdali depression.

Hydrogeology
In general, Kuwait has extremely low surface runoff due to the low precipitation and the dry sandy soils. However, due to severe storms, substantial short duration flows may develop in the areas of integrated surface drainage and accumulated as playa lakes. The accumulated water infiltrates through the Dibdibba Formation to form fresh groundwater lenses in the Kuwait Group in the northern part of the country at Ar-Raudhatain and Umm Al-Aish areas [11]. The lithology of the Kuwait Group controls its content of groundwater, as the existence of local isolated aquicludes (calcrete and/or or mud horizons) divides the Dibdibba Formation into two separate water-bearing horizons ( Figure 5 [15] and hydrogeological units of Kuwait region [16]; and (b) Lithostratigraphic succession for the Kuwait region [17].
flows towards the northeast [12] [13], notifying that upward leakage of groundwater from the Dammam aquifer to the overlying Kuwait Group was confirmed by isotope data [14].

The Late Pliocene/Early Pleistocene Phase
The last intense long humid period took place in late Pliocene/Early Pleistocene between 1.2 -3.5 million years BP. It is characterized by its intense chemical weathering and enormous fluviatile erosion and sedimentation processes from the mainly aeolian processes of the Quaternary. This is evident in the filled-up erosion channels of the ancient drainage system, and directly connected with them are the gravel fans, which declared long ago to the remnants of an intense humid period [18].

Field Investigation and Sampling
Using GIS and remote sensing data, topographic, aspect and slope directions maps were constructed for the drainage network in the study area showing the water divide and the catchment area along with the morphology, pattern, wadis, streams, ephemeral rivers, dry creeks, erosion gullies undulations, tributaries to the main streams, and basins of the well-developed paleo-drainage network carved in the study area.

Field Work
Six sites were located for digging vertical pit holes (

Basin Geology and Geomorphology
The portion of the precipitation which infiltrate may add to the moisture content of the soil or may become groundwater. The most influential factor in de- and sequence of rocks. To study the basin geomorphology, basin is described by introducing the concept of stream orders [21]. The drainage basin features of hydrologic importance are: elevation, stream length, basin perimeter, drainage area.

Morphometric Analysis Using ArcHydro GIS Technology and STRM
Analysis System To obtain information on the spatial variability in processes throughout a watershed requires delineation of the drainage system, which includes the stream channel network and smaller catchments within the basin.
In addition, every watershed can be characterized by geometric properties re- H Z z = − [22] Relief ratio: Relative relief ratio: Ruggedness number: Circularity ratio: Elongation ratio: Form factor ratio: Bifurcation ratio: Drainage density: Drainage frequency: where: and kurtosis. Interrelationships of these size parameters were constructed. Table   1 shows the mechanical analysis results along with the statistical textural parameters. The highest frequency mode was the bi-modal (10×), but the tri-modal and the polymodal recorded slightly lesser frequency (8×) and come last the uni-modal, which was a frequency only for 3 times. This means that the size dis-

X-Ray Fluorescence (XRF)
The XRF results obtained for the samples collected from the six vertical pit hole dug in the catchment area of the well-developed drainage network in the study area showed, on average basis, that the predominating oxide is SiO 2 , i.e., quartz, within the range (50.69% -37.03%). This range was remarkably quantitatively higher (big difference) than the range of the quantitatively following oxides CaO (20.81% -13.97%), SO 3

Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES)
The data obtained from this analysis showed that, on average basis, calcium (Ca)

Thin Sections
According to the analysis of the thin sections prepared from for selected bulk rocky samples extracted from the vertical pit holes, it was shown that these rocks are either calcretic lithic arenite, lithic arenite (greywacke), or wacke mud-supported sandstone. In general, all these rocks are very porous, where the pores are filled with mounting medium with carbonate mud as matrix and silica as cement in the form of quartz over growth. These rocks are formed as the result of rapid uplift and intense erosion and high rate of deposition as a flush. In almost all the samples the matrix clay is affected by varying degrees by carbonate replacement.
In some places there is also some kind of diagenetic replacement in carbonates.

Basin Geology and Geomorphology
The streams in the well-developed drainage system in the study area are of the ephemeral streams or dry washes that only occasionally have water flowing.
They are above the water table and occur in dry climates with low amounts of rainfall and high evaporation rates. They flow mostly during rare flash floods.
Using GIS and remote sensing techniques several maps were made for the drainage system in the study area (Figures 9-14), as well as a table showing the characteristics of the basins found in the drainage system of the study area (Table   2).

Morphometric Analysis and Characteristics Using ArcHydro GIS Technology and STRM Analysis System
As for the elongation rate, 3 groups were noticed (Table 3): 1) low rate (4 basins), Table 2. Characteristics of the 10 basins in the drainage system of the study area.  2) high rate ( Figure 15 shows the Correlation of the 6 stratigraphic columns constructed from the analysis of the samples taken from the 6 vertical pits from the study areas showing the 5 main dominant components: gravels (mainly quartz), sands, mud, calcite, and gypsum found in the 6 interpreted facies. The lateral and vertical distribution of these sediments is highly controlled by four major factors: general slope, local relief, drainage pattern and frequent storms. According to the lithofacies and stratigraphic correlation, it was found that the area is dominated by coarse-grained sediments with considerable fractions of gypsum, silts, and calcite. These types of loose sediment are characterized by high porosity and permeability, so the rate of infiltration is relatively high. Therefore, during frequent rain storms significant amounts of water may infiltrate through the sediments. This infiltrated water would have lower or limited chance to percolate due to the rigid underlying bed rocks and hence eventually directed to the sea A. Al-Hurban et al.

Interpretation of Stratigraphic Settings
driven by the general slope and dip of strata trending seaward. As a result, there is a very limited chance of recharging from the well-developed drainage network in the area to the shallow aquifers. Kuwait Group possesses a groundwater level that varies from about 80 to 90 m above sea level in the southwest to near ground level along the coast (2 -20 m in the study area) [3]. The calculated total gradient in the study area is about 0.214% seaward. The Ghyben-Herzberg relation (which states, for every 1 m of fresh water in an unconfined aquifer above sea level (as the case in the study area) (Figure 16), there will be 40 m meters of fresh water in the aquifer below Figure 15. Correlation of the 6 stratigraphic columns constructed from the analysis of the samples taken from the 6 vertical pits from the study areas showing the 5 main dominant components: gravels (mainly quartz), sands, mud, calcite, and gypsum found in the 6 interpreted facies. Figure 16. The Ghyben-Herzberg relation. Where the thickness of the freshwater zone above sea level is represented as h and that below sea level is represented as z (after [28]).  sea level). Accordingly, the movement of surface runoff and infiltrated water towards the sea is suggested to contribute in the stabilization of fresh water-saline water interface, and hence oppose the salt water intrusion, which consequently might play a significant role in enhance the water quality in the shallow aquifers ( Figure 17).

Conclusions
The well-developed paleo-drainage system in As Sabriyah area is composed of 10 closely spaced drainage basins, which are subparallel dendritic elongated variant-sloped and of high compactness coefficient, of an area of (13 -88 km 2 ), a length of (7 -18 Km), a width of (1. The hard resistant calcretic and gypretic gravelly sand deposits in the upper Dibdibba Formation lowered its infiltration and recharging capacity to the shallow aquifer, but retained the well-developed drainage network. Whereas the coarse-grained sediments with considerable fractions of gypsum, silts, and calcite of the friable gravelly sand or aeolian sand nature of the wadi fill deposits increased the infiltration capacity of the surface sediment. Thus, infiltrated water would have limited chance to percolate and eventually directed to the sea by the general topography of the area seaward, which would be of limiting potential recharge from the well-developed drainage network to the shallow aquifers.
According to Ghyben-Herzberg ratio for the fresh-salt water interface, the movement of surface runoff and infiltrated water towards the sea in the study area is suggested to contribute in the stabilization of fresh water-saline water interface, and hence oppose the salt water intrusion, which consequently might A. Al-Hurban et al. Journal of Geographic Information System play a significant role in enhancing the water quality in the shallow aquifers.

Recommendations
Any development management plan to be implemented in the study area should take into consideration the pattern and distribution of the well-developed paleodrainage network in the area for the following important issues: 1) Since surface runoff is of high potential to infiltrate through the surface wadi fills sediments of the drainage system in the area rather than the surrounding and underlying rigid calcretic gypcretic bedrock, the outcomes of this study should be considered for the morphometric characteristics of the existing drainage system as it is highly potential to play a significant role in water harvesting feasibility in the desert of Kuwait.
2) Knowing that such areas might be very susceptible to salt water intrusion due to pumping from the lower shallow aquifers, as if pumping lowers the water table by 1 m, the thickness of the freshwater body within the aquifer will decrease by approximately 40 m, according to Ghyben-Herzberg relation, thus allowing the denser saltwater at depth to "intrude" into the aquifer. Therefore, careful management of groundwater pumping in such areas is required to avoid the intrusion of saltwater into the freshwater aquifer.
3) The significant role of the well-developed drainage network in As Sabriyah area and its beneficiary contribution to hydrogeological matter of concern should be taken into consideration in any future developmental plans in the area.