Introduction

Currently, the northwestern Gulf of Suez Province is observing accelerated, sustainable development and many national projects implementation. Many essential infrastructures such as highways, ports, power plants, and urban extension are involved in those projects. Concurrently, the different risks, which may threat those developing projects, dictate conducting hazard assessment to mitigate its impacts on such projects.

There are different definitions of neotectonics (e.g., Mörner 1978; Pavlides 1989; AGI 2009), but the most common accepted one between researchers is the study of young tectonic movements. Furthermore, there is a disagreement on exactly how young they must be considered as neotectonics. Hancock and Williams (1986) proposed that neotectonics began when the present-day stress field of a region was started. Generally, it started between the Oligocene and Miocene periods, which matches Vita-Finzi’s (1986) brief definition of neotectonics as “Late Cainozoic tectonics.”

Neotectonic deformation was examined under a variety of headings, including tectonic geomorphology and seismotectonic. They can be found using multi-spectral satellite data combined with GIS, InSAR, and DEM techniques, as well as the extraction of geomorphic parameters. (e.g., Hancock and Williams 1986; Valkanou et al. 2021; Karaca et al. 2021).

Geomorphic parameters are among the basic inspection tools offering not only evidences on the regional tectonic deformation of specific area but also the tectonic activity level (Keller 1986; Keller and Pinter 1996; Demoulin 1998). The most important geomorphic parameters include the ratio of valley floor width to valley height (Vf), the stream length-gradient index (SL), the transverse topographic system (T), the hypsometric integral (HI), the drainage basin shape (Bs), and the asymmetric factor (Af) (e.g., El-Hamdouni et al. 2008; Buczek and Górnik 2020).

Mainly, the present study aims to investigate, analyze, and integrate the geomorphic and geological parameters and, hence, assess the neotectonics of Wadi Beda Main Basin and its sub-basins; Wadi Umm Athala, Wadi El-Noqra, and Wadi Umm Elda (Fig. 1). Such assessment sheds light on the hazardous sites that must be taken into consideration during the future development and urban planning of the Northwestern Gulf of Suez Province.

Fig. 1
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Location, DEM (elevation in meter), and fault-blocks map of the W. Beda Main Basin

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Several investigations have been carried out either at the whole northwestern Gulf of Suez Province or at a specific part of it. The morphometric analysis which was carried out by Arnous et al. (2011) strongly supported the high probability of flash flooding in different sites of the northwestern Gulf of Suez Province. Geriesh et al. (2004) suggested a suitable management system to control its huge runoff quantities based on an estimation of the flood risks of Wadi Ghoweiba Basin. El-Behiry et al. (2006) deciphered the flash flood risk zones and established an effective hazard mitigation scheme based on the analysis of runoff hazard of the Ain Sukhna industrial area and delineated the drainage networks for predicting surface water runoff. El-Rayes et al. (2009) proposed a system composed of a group of cisterns, retention, and reservoir dams in addition to mitigation canals to control the huge runoff quantities of water at Wadi Hagul Basin. Seleem and Aboulela (2011) evaluated deformation and surface break at the Wadi Hagul area and gave a new insight for understanding and assessment of the seismic hazard. Arnous et al. (2011) concluded that the seismic activity in the northwestern Gulf of Suez region markedly increases from north to south. Hegazi et al. (2013) revealed that the Bitter Lakes area, including Wadi Beda Basin, display four alternating NW-trending seismic zones characterized by unique motion. Two of these seismic zones (III and IV) are displayed at the present study area (Fig. 2). El-Rayes et al. (2015) address the correlation between seismological data and the geographic distribution of geothermal fields in the neighboring South Sinai. They concluded that the distribution of recent earthquake epicenters over South Sinai reveals three broad active trends (N 6° E, N 40°–75° E, and N 50°–60° W), which are consistent with the long fault extensions and include the well-known hot springs in the region. Omran et al. (2021) examine the connection between seismic activity and the potential of rock fall in the nearby South Sinai. They demonstrate that the possible occurrence of rock fall is highly sensitive to the depth of seismic activity, geology, and lineament density.

Fig. 2
figure 2

Seismotectonic map of Bitter Lake area (Hegazi et al. 2013)

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These previously published investigations have been focused either on seismic, tectonic, runoff, or flash flood parameters. None of them has taken into consideration the integration between the different geomorphic and geological parameters in order to evaluate the neotectonics at the study area.

The goal of the current study is to examine, analyze, and integrate geological and geomorphic parameters in order to assess the neotectonics of the W. Beda Main Basin and its sub-basins, W. Umm Athala, W. El-Noqra, and W. Umm Elda. Such a neotectonic assessment sheds light on the hazardous sites that must be addressed for the future development and urban planning of the Northwestern Gulf of Suez Province.

General geology

Wadi Beda main Basin belongs to the Northwestern Gulf of Suez Province, and it encompasses three sub-basins: the Wadi Umm Athala, Wadi El-Noqra, and Wadi Umm Elda. The Wadi Beda main Basin is bounded by longitudes 32° 22′ and 32° 55′ E and latitudes 29° 41′ and 29° 59′ N, covering an area of about 800 km2 (Fig. 1).

Many highlands are encountered in the present study area such as Gebel Ataqa block (900 m a.s.l.) to the northeast, and El-Galala El-Bahariya Plateau (1332 m a.s.l.) to the south as well as the Wadi Beda main basin (Fig. 1), and several sub-basins, e.g., Wadi El-Noqra, Wadi Umm Athala, and Wadi Umm Elda.

The exposed rocks at the study area belong to Phanerozoic Era, where they are ranging in age from Eocene to Recent time (Fig. 3). Structurally, the Northwestern Gulf of Suez Province, including the present study area, represents a series of alternating positive and negative fault-blocks which are bounded by ENE-trending faults (Abd El-Rahman and El-Etr 1979). Three of these blocks are identified at the study area; the two positive blocks (topographically high) are El-Galala El-Bahariya Plateau and Gebel Ataqa, whereas the negative block (topographically low) is Wadi Akheider (Fig. 1). Gamal et al. (2021) revealed that competent rock units (Middle Eocene limestone) of Gebel Akheider forming horsts and grabens relay zones, while incompetent rock units (Middle Miocene soft marl and sandy limestone), of Wadi Akheider forming a series of en echelon plunging anticlines and synclines (accommodation folds). Also, several faults are reported in the study area which are principally related to the tectonics of the Gulf of Suez Rift (Figs. 4 and 5). They are categorized under three main sets of faults; these are NW-, E-W-, and NNW-trending sets. The NW-trending set is the most prominent one in the study area (Fig. 3) (Abdallah 1993; Youssef and Abdallah 2003).

Fig. 3
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Geological map of the Northwestern Gulf of Suez (Al-Moazamy 2018)

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Fig. 4
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Photograph showing dip-slip normal fault (320°/58°SW) and its extension (looking southeast)

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Fig. 5
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Photograph showing dip-slip normal fault (290°/74°NE), (looking north)

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Materials and methods

Microwave data such as Shuttle Radar Topography Mission (SRTM) images provide a rapid and low-expensive means to analyze and interpret regional geomorphic features (Grohmann et al. 2007). These data are commonly used in accomplishment of digital terrain models, such as shaded relief (Chorowicz et al. 1998; Jordan et al. 2005; Nureddin et al. 2009; and Abdel Kareem et al. 2011). They also provide crucial information for morphotectonic analysis such as geomorphic parameters, drainage asymmetry and networks, and stream orders.

In the current investigation, the SRTM images have been used in producing DEM, contour, and relief maps and extracting drainage networks of the study area. Furthermore, a 3D-perspective with image draping could be useful for the morphotectonic investigations and to sharpen the topography, particularly for cases where the topographic data and optical images are integrated (Le Turdu et al. 1995; Jordan et al. 2005).

The geomorphic and geological parameters

Valley floor width to height (V f) index (Fig. 6)

Fig. 6
figure 6

The effective parameters used in calculating Vf index (Vfw: width of the floor; Eld: elevation of left divide; Erd: elevation of right divide; Esc: elevation of the floor)

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The (Vf) index was calculated as follows:

$${V}_{f}={2V}_{fw}/\left[\left({E}_{ld}-{E}_{sc}\right)+\left({E}_{rd}-{E}_{sc}\right)\right]$$
(1)

where Vfw is the width of the floor, Eld and Erd are the elevations of left and right divides, respectively, looking downstream, and Esc is the elevation of the floor.

Stream length-gradient index (S L)

The (SL) index was computed based on Hack's Eq. (1973) as follows:

$${S}_{L}=\left(\Delta H/\Delta L\right)L$$
(2)

where ΔΗ/ΔL is the stream gradient at a specific reach (point) in the channel, ΔΗ is the change in elevation of the reach, ΔL is the length of the reach, and L is the channel length from the divide to the midpoint of the channel reach.

Transverse topographic symmetry index (T):

The (T) index was calculated regarding the larger axis of the basin as follows:

$$\mathrm{T}={\mathrm{D}}_{\mathrm{a}}/{\mathrm{D}}_{\mathrm{d}}$$
(3)

where Da is the distance from the basin midline to the active meander-belt midline, and Dd is the basin divide.

Hypsometry index (H i)

The (Hi) index was calculated relied on Pike and Wilson’s Eq. (1971) as follows:

$${H}_{i}=\left({h}_{mean}-{h}_{min}\right)/\left({h}_{max}-{h}_{min}\right)$$
(4)

where hmax, hmin, and hmean are the maximum, the minimum, and the mean elevation, respectively.

Drainage basin shape (B s)

The (Bs) index, based on Ramirez-Herrera (1998), can be formulated as

$${B}_{s}={B}_{l}/{B}_{w}$$
(5)

where Bl is the length of the basin measured from the headwater to the outlet, and Bw is the basin width in the widest point of the basin.

Structural lineaments

Lineaments have been extracted from the enhanced STRM images, analyzed, and integrated with lineament parameters (length, number, and directional families). Linear-features extraction is executed by manual lineaments extraction, where the confirmed structural lineaments are extracted from different enhanced satellite images by using visual interpretation. The resulted structural lineaments map of the study area is shown in Fig. 7.

Fig. 7
figure 7

Structural lineament map of the W. Beda Main Basin

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Seismicity data

The epicenters, which have been detected at the study area during the last century (1900–2003) (Earthquake catalog of Egypt, 1900–2003), are displayed on the map, which is shown in Fig. 8. The uniformity and incompleteness of seismological data has been carried out based on an equation proposed by Al-Ibiary (2000):

$${P}_{k}=\left(10/N\right)\sum \left({I}_{k}^{i}/{I}^{i,max}\right)$$
(6)

where N is the number of observation, Ii indications of the seismic intensity at Kth location for ith earthquake, and Ii,max is the observed maximum intensity for the ith earthquake.

Fig. 8
figure 8

Epicenters distribution map of the W. Beda Main Basin

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Results and discussion

The attained results of geomorphic parameters are discussed in this section. The sub-basins of Wadi Beda Basin along with the transverse topographic profiles on which the measurements carried out are shown in Fig. 9. An example of the extracted topographic profiles and the structural cross-sections of the different sub-basins (based on field mapping), the topographic profiles of Wadi El-Noqra sub-basin are shown in Fig. 10.

Fig. 9
figure 9

The transverse topographic profiles of Wadi Beda basin and sub-basins

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Fig. 10
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Topographic profiles and structural section of W. El-Noqra sub-basin (looking downstream) (blue arrow) W. Umm Elda (red arrow) and sense of movement along faults (black arrows)

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The geomorphic and geological parameters

Generally, the distribution map of the Vf index shows a tendency to increase from the upstream to the downstream (Fig. 11). However, Wadi Umm Elda and Wadi El-Noqra have relatively low Vf values (0.50–1.09) and (0.43–1.03) (Table 1), respectively; indicating a high rate of tectonic activity (displacement of faults) along the Wadi course. While Wadi Beda main basin (2.63–14.19) and Wadi Umm Athala sub-basin (0.43–11.95) are representing ideal cases for the tendency to be gradually-increased from upstream to downstream. The Vf values of those sub-basins start low at their upstream and then gradually increase and become higher near the mountain fronts indicating broad valley floors and lateral cutting of the streams.

Fig. 11
figure 11

Valley floor width to height (Vf) index of the W. Beda Main Basin

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Table 1 The calculations of (Vf) index of sub-basins
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The Vf index was originally used to distinguish V-shaped valleys from U-shaped valleys (Bull and McFadden 1977). Wadi Umm Elda is U-shaped at the upstream, whereas as it becomes V-shaped at the downstream. On the other hand, Wadi El-Noqra and Wadi Umm Athala have V-shaped valleys and are considered areas of active uplift and deep, linear stream incision. Wadi Beda main has a wider and flat floor across its course. The relatively high Vf values indicate tectonically stable areas where stream valley bottom tend to be flat and wider and eroding laterally into the adjacent hill slopes. The V-shaped valleys are due to the sculpting of streams along the NW-trending faults related to the tectonics of Gulf of Suez Rift (Fig. 3), as an example of these valleys is Wadi El-Noqra which is pursuing its course along one of the rift-related graben (Fig. 12). The careful examination of the geometry of that graben shows the presence of slightly tilted fault-blocks toward the SW direction, and hence, slightly shifting of valley course toward the same direction.

Fig. 12
figure 12

Geologic cross section showing Wadi El-Noqra graben Suez/southern Galala Fm (after El-Akkad and Abdallah 1971) (Vertical exaggeration: 6.6X)

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The SL index investigates the relationships between tectonic activity, rock resistance, and topography expressed by sudden changes in channel slope. The differences in the SL values indicate changes in the longitudinal profile of a stream and hence reflect the possible tectonic activity. Baruah et al. (2020) concluded that both stream length gradient index (SL) and steepness index (SI) have their common genetic relationship between the surface uplift and response of any channel gradient to it.

The distribution map of the SL index (Fig. 13) shows a tendency to increase from the upstream to downstream. Based on the attained results, SL parameters change between 23.84 and 287.02 (Table 2). The streams display a smoothly changing, concave longitudinal profile, except some locations that are tectonically perturbed (Fig. 14). The SL values are low at upstream and suddenly became high at sites where streams crossing fault and then gradually increase to reach the maximum value at the downstream. Such perturbations in stream profiles could be attributed to tectonic activity, namely, E-W-trending normal faulting (Fig. 3).

Fig. 13
figure 13

Stream length-gradient index (SL) values W. Beda Main Basin

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Table 2 Calculations of the stream length-gradient index (SL) of sub-basins
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Fig. 14
figure 14

Longitudinal profile along the main stream of W. El-Noqra (arrow: site of perturbations)

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Transverse topographic symmetry factor (T) is used for determining the possible tilt direction (e.g., El-Hamdouni et al. 2008), where the perfectly symmetric basin has a value of transverse topographic symmetry (T) equals zero, as the asymmetry increases, (T) increases and approaches the value of one. The distribution map of the factor (T) shows that the Wadi Beda is moderately asymmetric (Fig. 15), except for some highly asymmetrical parts of the streams, in which the factor approaches one (0.93) (Table 3). An exception to these results is encountered in the middle part of Wadi El-Noqra and downstream stream of Wadi Umm Athala where (T) values approach zero, indicating symmetry (Table 3) (Fig. 15).

Fig. 15
figure 15

Distribution map of transverse topographic symmetry factor (T) of the W. Beda Main Basin

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Table 3 Calculations of transverse topographic symmetry factor (T) of sub-basins
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The asymmetry of the sub-basins could be interpreted in terms of the regional tectonic setting of the North-western Gulf of Suez Province. Where tilted fault-blocks style is prevailing, in which blocks between roughly parallel faults are subjected to tilting. The tilting produces mountains and intervening valleys. Three tilted fault blocks are exposed in the study area; these are Gebel Ataqa, Gebel Abu Treifiya-Khahaliya-Umm Zeita, and Gebel Qattamiya, which are separated by three main wadis; Wadi Hagul, Wadi Beda, and Wadi Ghoweiba (Fig. 3). These three tilted fault blocks are composed of Eocene to Miocene rocks are affected by E-W elongated belts of left-stepped en echelon normal faults. These belts act as transfer zones between NW oriented normal faults synchronous with faults of the same trend in the Suez rift (Moustafa and Abd-Allah 1992; Moustafa et al. 1998).

The attained results (Table 4) indicate that HI values are intermediate and are associated with a more evenly dissected drainage basin. Values obtained for the previously mentioned basins and sub-basins of the hypsometric integral ranges between 0.403 and 0.541. These values indicate that Wadi El-Noqra and Wadi Umm Athala are in the mature stage. Moreover, these values fall in the range of 0.3 ≤ HI ≤ 0.6 of Keller and Pinter (2002), which means that the watershed is susceptible to erosion (equilibrium or mature stage). However, the values of 0.52 and 0.54 obtained for Wadi Beda basin and Wadi Umm Elda sub-basin indicate that they are near to the lower limit of the youth stage, in other words, they are highly susceptible to erosion.

Table 4 Calculations of the hypsometric integral values (HI) of W. Beda Basin and its sub-basins
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The (Bs) values range from 1.84 to 2.89 (Table 5), which seems to have moderate tectonic activity, except for Wadi Umm Elda which is displaying relatively higher value. High values of Bs are associated with elongated basins, generally associated with relatively higher tectonic activity. Low values of Bs indicate a more circular-shaped basin, generally associated with low tectonic activity (e.g., El-Hamdouni et al. 2008; Buczek and Górnik 2020). The elongated drainage basins are considered to be relatively young and are commonly encountered in active tectonic areas and could be primarily due to the downcutting of the stream (Bull and McFadden 1977).

Table 5 Calculations of the drainage basin shape (Bs) values of W. Beda Basin and its sub-basins
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The directional set parameters were treated independently and each direction is given a definite weight value, based on its relative abundance in the study area. Four directional families are recorded, and they are NW, NNW, WNW, and NE. Furthermore, the weighting values assigned to each direction are as follow: NW (15%), NNW (15%), WNW (5%), NE (5%), NS (2.5%), NNE (2.5%), ENE (2.5%), and EW (2.5%). The sum of weighted values of the three lineament parameters, length, number and directional groups, is considered the photo-lineaments factor values that are displayed as an integrated colored map (Fig. 16). The photo-lineament factor map exhibits areas of high anomalies that are varying in extensions and size and are most likely underlain by highly fractured rocks. Areas of high anomalies are located at three sites, two of them locate at the upstream Wadi Umm Athala, and the third one at the northeast border of the Wadi Beda main basin. The low anomalies over Gebel El-Ramliya, Gebel Akheider can be interpreted, in terms of the three lineament parameters, as areas characterized by short, low abundant and low-weighted lineaments.

Fig. 16
figure 16

Photolineament factor map of the Wadi Beda Main Basin

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The resulted seismic intensity map of the study area is shown in Fig. 17. An examination of the map reveals the presence of large areas with high to very high seismic intensity. Gebel El-Noqra, Gebel El-Ramliya, Gebel Akheider, and Gebel Umm Zeita are the locations of these areas. The research area’s reminder has low and moderate seismic intensities.

Fig. 17
figure 17

The seismic intensity map of the Wadi Beda Main Basin

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The integrated thematic map

The map assigned weights and the geomorphic potentiality values of Wadi Beda Basin are listed in Table 6. The thematic map of Wadi Beda Main Basin (Fig. 18) was produced by integrating the different geomorphic and geological parameters, based on these assigned weights and potentialities. Careful inspection of the integrated thematic map discloses that the majority of the study area exhibits a moderate-active zone (83.4%), whereas some areas display low-active zone (11.10%), and other areas display high-active zone (5.5%) (Table 7). Specifically, three definite high-active spots could be recognized; these are.

  1. 1.

    Gebel Umm Zeita and downstream of Wadi Umm Athala

  2. 2.

    Gebel Akheider and downstream of Wadi Akheider

  3. 3.

    Gebel El- Ramliya and downstream of Wadi El-Noqra

Table 6 Thematic map weight and geomorphic potentiality values of W. Beda Basin area
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Fig. 18
figure 18

The thematic map of integrated geomorphic and geological parameters of the Wadi Beda Main Basin

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Table 7 The calculations of active area of W. Beda Basin
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Based on the weighted basin and channel geomorphometric parameters (circularity, basin length, basin area, basin perimeter, bifurcation ratio, drainage density, and stream frequency), the Wadi Beda Main Basin was given a moderate rank of flood potentiality (Arnous et al. 2022). This moderate rank indicates that Wadi Beda Main Basin is not capable to collect high quantity of runoff water, and hence, a low quantity of water moves out the basin, which is low-risk Basin.

The high-active areas are characterized by the presence of E-W belt of left steeped en-echelon normal faults and WNW to NW-oriented normal faults and very high seismic intensities (Figs. 3 and 7). The E-W faults have a left-stepped en-echelon arrangement belts which are proposed to overlie E-W deep-seated faults. Moreover, these deep-seated faults have been rejuvenated by right-lateral wrenching during the early phases of opening of the Suez rift (Early Miocene) (Moustafa and Abdallah 1991; Abdallah 1993). Aeromagnetic data confirmed that the Gulf of Suez region appears to be a small down-lifted block dragged down between the larger faults (Abuelnaga et al. 2019).

It is clear that the main tectonic trends, which have affected the study area, are the NW-trending Faults and E-W-trending faults. Hegazi et al. (2013) correlated these trends with the well-known tectonic events affecting Egypt. The NW-trending faults are related to the Gulf of Suez rifting (Oligocene – Early Miocene). Whereas the E-W-oriented faults were mostly originally formed in Late Triassic-Early Jurassic during the rifting of the African-Arabian plate away from the Eurasian plate. These faults were reactivated to deform the upper Cretaceous rocks and continued to affect the overlying Tertiary rocks. The intersections of these two trends represent sites of high clustering of epicenters. The majority of drainage lines in the Wadi Beda Main Basin are controlled by NW-trending faults, and the sites of perturbation are localized at the intersections with the E-W-trending faults, which make them high-risky zones.

According to the integrated geo-environmental hazards map of the northwestern Gulf of Suez area (Al-Moazamy 2018), the Wadi Beda Main Basin has flash flood and seismo-tectonic threats (Fig. 19). The unpredictable nature of flash floods makes detecting, analyzing and predicting them a unique problem. The best mitigation approach for flash flood threats is the construction of retardation dams, the digging of artificial basins to collect floodwater, or the excavation of retention cisterns along high-risk wadis in order to mitigate the massive losses and problems caused by flash floods.

Fig. 19
figure 19

Map showing the integrated hazards map of the Northwestern Gulf of Suez Region (Al-Moazamy 2018)

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Summary and conclusion

The present study aims at investigate, analyze and integrate the geomorphic and geological parameters, and hence assess the tectonic activity of Wadi Beda Main Basin and its sub-basins; Wadi Umm Athala, Wadi El-Noqra, and Wadi Umm Elda.

The Shuttle Radar Topography Mission (SRTM) images have been used in producing DEM, contour, and relief maps and extracting drainage networks a 3D-perspective model of the study area. The geomorphic parameters include valley floor width to height (Vf) index, stream length-gradient index (SL), transverse topographic symmetry index (T), hypsometry index (Hi), and drainage basin shape (Bs). Whereas the geological parameters are the structural lineaments, and in addition to seismicity data.

The distribution maps of Vf index, SL index, factor (T), photo-lineament factor, and seismic intensity have been integrated to produce a thematic map of Wadi Beda Main Basin. This thematic map shows that the majority of the study area exhibits a moderate-active zone (83.4%), whereas some areas display low-active zone (11.10%), and other areas display high-active zone (5.5%). Specifically, three definite high-active spots could be recognized; these are Gebel Umm Zeita and downstream of Wadi Umm Athala, Gebel Akheider and downstream of Wadi Akheider and Gebel El-Ramliya and downstream of Wadi El-Noqra. These high-active areas are characterized by the presence of E-W belt of left steeped en-echelon normal faults and WNW to NW-oriented normal faults and very high seismic intensities. It is clear that the main tectonic trends, which have affected the study area, are the NW-trending faults related to Gulf of Suez Rift (Oligocene – Early Miocene), and E-W-trending faults mostly originally formed in Late Triassic-Early Jurassic during the rifting of the African-Arabian plate away from the Eurasian plate. The intersections of these two trends represent sites of high clustering of epicenters and represent highly-active-zones.