Wadi Al-Shumar catchment was divided into seven sub-catchments as given in Figure 3; these are Wadi Al-Shumar, Braiqa, Mashqam, Zarnouk, West of Ramtha, Al-Shiah, and Al-Mashro.

Analysis of the linear aspects in this study includes the Area (A), Perimeter (P), Basin Length (Lb) and the number of stream. Table 2 shows the linear aspects values of the catchments and the sub-catchments. The results show that

the area of sub-catchments ranges from 15 to 329 km², while the perimeter of the sub-catchments ranges from 27 to 187 km. These relationships indicate a significant difference between shape properties on the sub-catchments level. The basin length is the horizontal distance between the upstream and downstream points of the metric basin [33]; in this study, the length of the main valley in Al-Shumar catchment is 37.6 km. On the other hand, the ponds’ length for other sub-catchments ranges from 6.5 km in Wadi Al-Shayyah to 14.6 km in Wadi Mashqum sub-catchment.

Stream order and number (Nu) is defined as a measure of the position of a stream in the hierarchy of tributaries. The classifications of streams are being useful indicators of stream size, discharge and drainage area [28]. The concourse of tributaries of the second level cause the formation of a tributary of the third rank, while the tributaries begin to form with each other at the confluence of the small water channels building a higher river tributary than the rank [33]. High number of tributaries in the catchment are attributed to the amount of precipitation and low-vegetation density in the river catchment environment.

The river tributaries are used as a logical indication of the formation related to river tributaries of large river ranks [29]. The analysis of the DEM data of the study area revealed that the total number of river canals of the main study catchment was 489 strands of different ranks, which indicates that the study basin is classified as a fifth level basin. While the number of streams of the first class is 321 tributaries which accounted for 65.6% of the total number of water network ways, it is noticeable that the number of waterways decreases by the river level as shown in Figure 4.

Stream length (Lu) indicates the contributing area of the basin for a given order [29]. The length of stream segments is high for first order streams and decreases as the stream order increases. The total length of the catchment tributaries is 521 Km, with the length of first-class tributaries reaching 8.18 km, the second reaching 0.838 km, the third reaching 4 km and the fourth is 4.67 km, while the fifth is 37.78 km.

The length of the lower stratum is 50.4% of the length of the tributaries, with

23% for the third, 13.9% for the fourth, 5.3% for the fifth, and 7.2% for the tributaries. This means that the tributaries of the lower levels are of low length values as shown in Figure 5, and they increase with increasing the level of rank that they represent.

Stream length ratio (RL) is the ratio of the average length of the one order to the next lower order of the stream segments [29]. The stream length ratio, among (7) sub-watersheds, varies from 0.456 to 1.384. The fourth-level ponds were between 34 and 1.902. This difference in values explains the change in the falling value of the basins. The analysis shows that the level of relief increases on the southern side of the basin and it decreases as moving towards the northern direction, which leads to an increase in the soil erosion severity in the basin.

Bifurcation ratio (Rb) is defined according to [36] as a ratio of the number of streams of a given order (Nu) to the number of streams of the next higher order (Nu + 1). In this study, the bifurcation ratio fluctuates in Wadi Al-Shumar basin from 2.2 to 7.9, but the average bifurcation ratio (Rbm) is 3.71. On the other hand, the RB ratio of the sub-catchments ranges from 1.56 to 11.5, and the Rbm value ranges between 2.679 and 4.434. According to the above results, one of the fourth-level basins has emerged from narrowing, which has a class value of RBM up to 3 - 5. This means that this time is susceptible to rapid seasonal floods, while other basins are geologically homogenous and are still vertically and horizontally capable of absorbing movements.

Under these conditions, the flash floods, which may suddenly form in arid and semi-arid regions, can be considered as one of the most dangerous geomorphological hazards to human constructions. It forms because of rapid watercourses with a relatively large hierarchical classification, which leads to high soil erosion rate in the basin and a great loss of plant and animal wealth [3].

Analysis of the areal aspects includes the drainage density (Dd), Drainage texture

(Dt), Stream frequency (Fs), Elongation ratio (Re), Lemniscate Ratio (K), and Form factor (Rf). Table 3 shows the areal aspects of values of the catchments and the sub-catchments.

The drainage density (Dd) is a measure of total stream length over the total area in a given basin [36]. It is affected by the factors that control the characteristic of watershed length and it is one of the most significant morphometric variables that explains the volume of water flow within the main and sub-tributaries of the basin [37]. Slope factor, soil permeability and resistance of surface materials are the main factors influencing this variable. Kant et al. classify the draining density value into three categories, these are, the low, medium and high classes [38]. In this study, the drainage density value of the catchments and sub-catchments ranges between 1.49 and 1.85 as shown in Table 3. These values are classified in the low discharge ponds.

The drainage texture (Dt) is the relative spacing of the streams in a unit area along a linear horizontal distance between water tributaries of the basin [31] [39]. It depends on the geological structure, soil types, vegetation cover, relief, infiltration rate and the amount of precipitation in the basin [29] [40].

The value of this variable is explained by the structure and nature of the river sediments that scattered in the estuary. According to Smith’s classification, the value of sediment thickness can be summarized as following: Less than 2 corresponds to very rough, 2 - 4 corresponds to rough, 4 - 6 is average roughness, 6-8 is fine, while more than 8 correspond to very fine. In this study, the value of the pelvic texture in Wadi Al-Shumer basin is 2.6, which is classified as rough, while the rest of the sub-basins ranged between 0.73 and 1.56, which were classified as very rough.

Stream frequency (Fs) is the ratio of waterways in the river basin to the basin area, where the variable explains the ability of falling water to cause surface water runoff in the structure of the basin [41]. In addition, this value can explain the percentage of water that leaked to the soil profile to enhance groundwater resources. In this study, the river recurrence value in Wadi Al-Shumar basin was 1.4, while in the other sub-basins it fluctuated between 1.44 and 1.83. The relatively

low values that can be explained due to the existence of the basin under semi-arid conditions and receive low amounts of precipitation, which is the main factor influencing the stream frequency.

Elongation ratio (Re) is the ratio of diameter (D) of a circle of the same area as the basin (A) to the basin length (L) [32] [33]. It reflects the variations of geological and climatic composition of the basin structure, and the presence of steep slopes in the catchment [30], and varies according to the age of the basin [42]. The elongation ratio varies from zero, which indicates a highly elongated basin with low relief, to a ratio of one, that point out to the presence of a circular basin with high relief [43] [44]. The higher value of elongation ratio of a basin the higher the indication of an active denudation process that is accompanied by high infiltration capacity and low run-off in the basin. On the other hand, a low Re value is indicative of higher elevation of the basin, a susceptible-to-high head-ward erosion along with indications of tectonic lineaments [45]. The elongation value of Wadi Al-Shumar basin ranges from 0.54 to 0.47, while the rest of the ponds range from 0.37 to 0.71. This indicates that these ponds are closer to the rectangular shape than the circular shape; therefore, Al-Shumar valley is classified as a rectangular shape and the rest of the ponds are classified as elongated and very elongated.

Lemniscate Ratio (K) value varies between 0 - 1; it is used to facilitate the interpretation of the life stage and the erosion cycle of the basin [31]. In this study, the value of K in Al-Shumer catchment is 1.07 and ranges between 0.62 - 2.28 in the rest of the sub-basins.

These results show that the sub-catchments are mostly formed the rectangle shape and they are still in the early period of its erosion cycle, which can be developed with the structure of the basin.

Form factor (Rf), is the coefficient of basin shape which is associated with the area factor and the pelvic length square [41]. This form factor variable helps to predict the flood hazards and the ability of water to carry mud deposits from the upstream to the downstream position. In most of the morphometric studies, the reference value of the shape of coefficient ranges from 0.1 to 0.8. The form factor value of the Wadi Al-Shumar catchments is 0.23 while in the rest of the sub-catchments is in the range from 0.11 to 0.40. The form factor variable value that is close to 0.8 indicates the rotation of the basin, which causes speediness degree of exposure to the flood risk and vice versa [45]. In this study, the form factor value is near the rectangular shape except for the Shihya sub-catchment, which is equal to 0.37 and the Hernouk sub-catchment with value of 0.40. These sub-catchments values are close to the circular shape and therefore they are vulnerable to flood risk in case of frequent rainfall events.

Analysis of the relief factor includes the basin relief (Bh), relief ratio (Rr), Ruggedness number (Rn), and Dissection index (Dis). Table 4 presents the relief aspects values of the catchments and the sub-catchments.

Basin relief (Bh) variable indicates the value of the height difference between

the lowest and the highest area in the basin structure, and it explains the similarity and differences in the spatial environment of the basin. This value relates to the geological structure, extent of rock resistance against the fragmentation processes, and to the impact on the sediments’ quality (4). The steep slope is closely related to the geological structure and the ability of rocks to resist the erosion, however, the high value indicates a very steep and high erosion force [5]. In this study, the basin relief was extracted from the DEM, and the value of it is in the range from 756 m in the main catchment to 126 m in the west of Ramtha sub-catchment.

These values display that these ponds are still able of carving streams and river valleys, and able of increasing the rock carving as well.

The concept of the Relief Ratio (Rr) has been introduced in the interpretation of morphometric variables by [31], as a dimensionless ratio between basin relief and basin length and widely accepted as an effective measure of gradient aspects of the watershed [46]. The relief ratio indicates the overall steepness of a drainage basin and is an indicator of the intensity of erosional processes operating on the slopes of the basin [22]. This increase in the sediments’ amount is resulting from the flow of the river level horizontally and vertically; thus, ponds are added to the stage that it reaches in the current cycle. The rate of relief at Wadi Al-Shumar basin was 20.11 meters, while the lowest value in the sub-catchments was 14.37, and the highest was 36.66. These values indicate that there is a significant erosion force resulting from the erosion processes with a high slope value.

Ruggedness number (Rn) is one of the morphometric variables that was obtained from the total density of the river drainage [39] [41]. This variable provides explanation of the positive relationship between the total calcification and density of drainage in the catchment. In general, the increase in the value of rationale pruning that is associated with an increase in the degree of roughening reflects the age of the erosion cycle in the catchment. The high degree of roughening means an increase in the capacity of water for soil erosion, and consequently, an increase in the river load of the sediments [24]. In this study, the degree of ruggedness was found to be 1.19 in the main catchment, while in the secondary ponds it ranges between 0.18 and 0.72; which means that Al-Shumar catchment is characterized by the value greater than (1) that represents a high roughness level. On the other hand, the other sub-catchments were classified as low-reared, and two other basins were medium-bumped. These results can be explained by the difference in the geological structures across sub-catchments, which directly affect the degree of basins roughness. Accordingly, the northern and eastern areas of the catchment were characterized as low pelvic areas and by a low bump degree.

Dissection index (Dis) is the vertical depth indication of the effective morphometric variables and which is considered an effective measure in determining water viability to make a change in the vertical depth of the river channel. The value of the (Dis) variable varies from (0 - 1); where the value of (1) shows a strong vertical setting, the value of (0) shows a weaker one. In this study, the vertical depth value was 0.74 of Wadi Al-Shumar catchment. This indicates a deep vertical depth that is directly linked to the high level of pelvic drainage and the relatively small catchment area.

These results suggest that Wadi Al-Shumar basin suffers from the exposure of the soil to erosion risk, in addition to the conclusion suggesting that the spreading risk of soil erosion is resulting from heavy rainstorms and low coverage of vegetation under semi-arid areas.