1 Introduction

The trend of urbanization has resulted in considerable changes in landscape patterns and land cover in the majority of geographical areas globally [1]. Simultaneously, it has had a number of detrimental effects on the physical landscape, including agricultural land loss, degradation of ground and surface water, alterations to geomorphic attributes, flooding, and landslides. Human-induced modifications to landforms and the mechanisms involved in shaping the landforms have reached an alarming point [2]. Even though the environment functions and provides all the services driving life, humans modify the landscape in multiple ways to satisfy everyday needs. Humans are actors, and landscapes are symbolic representations of nature and the environment [3]. The fundamental concern of urban planning and management agencies is planning for cities, especially in this twenty-first century, where there is rapid urbanization and accelerated urban expansion [4]. However, planning for cities does not come easy, especially in areas where geomorphological features such as geology, hydrology, elevation, aspects, slope, and soil are predominantly less favourable for construction [5]. On a worldwide scale, urban landscapes are predicted to occupy 1.3% of the world's surface (Cole 2019, cited in [6]); thus, there is a need to properly transform the remaining virgin land to meet the demands of the increasing number of people. Global population growth, industrialization, economic expansion, haphazard development, loose land tenure, and government initiatives across the world have collectively led to an increase in urban land usage beyond measure (Ferreira and Feres 2020; Liu et al. 2020; Chen et al. 2016 as cited by [6]). Since urban built-up areas are highly irreversible to natural ecology, planning urban land use is strategically necessary for predicting future land consumption, especially in less developed countries [7]. In developing countries, cities are regarded as economic indicators for growth and development, hence the high rate of urbanization and urban expansion [8]. However, urban land has been utilized in the form of sprawl, where there is massive uncontrolled, unplanned and excessive development that interacts with geomorphological characteristics and processes that inhibit balance in the natural system (Csima 2010; Thornbush 2015) as cited in [9].

Ghana continues to increase its urban population; a 5.8% growth rate was recorded between 2010 and 2021. Greater Accra and Ashanti region takes up to 47.8% of the total urban population of Ghana [10]. This is alarming since most cities experiencing urban sprawl have exceeded the expected rate of most urbanized regions worldwide [8]. The Weija-Gbawe Municipality, located within the Greater Accra Region of Ghana, has recently experienced significant urban growth and development-oriented activities and structures like buildings or settlements, construction of roads, destruction of forests, and other human-caused attributes influencing the geomorphological landforms [6]). This has altered and increased land use, and land cover modification changed consumption rates of the area’s landmass. Relevant studies in the area have failed to provide a more detailed attempt to understand, evaluate and predict any possible future changes. This research, therefore, seeks to analyse the changes that have occurred over time with specific evidence. In addition, the study intends to provide appropriate proof of geomorphic elements and a policy framework that would guide or explain urban geomorphological dynamics. Geomorphological features and processes can either restrict, regulate and control the trajectory of urban expansion or worsen the inherent risks of inhabited spaces. Daoudi and Niang [11] hold the view that considerable city planning and placement typically depend on socioeconomic and strategic considerations. However, many works have been done to explore and understand the dynamics of urban expansion and its related management globally. The research works in Ghana by researchers such as [6, 12,13,14] emphasized the dynamics of urban expansion from an urban planning perspective in their respective studies. These works did not examine geomorphological impacts on urban development. The novelty of the current research is its scope, as most studies reviewed in Ghana are not concerned about the nexus of geomorphological and anthropogenic influences on the landscape and vice versa. The many natural-geomorphological variables that must be incorporated amongst the targets of a strategic approach for growing urban regions and protecting them from geomorphological dangers will be encountered in defining and monitoring the trajectory of urban development.

The paper is built on three main objectives. These are to:

  1. 1.

    Assess human influence on the geomorphological features of Weija-Gbawe Municipality,

  2. 2.

    Analyse geomorphological impacts on the urban expansion of the Weija-Gbawe Municipality, and finally,

  3. 3.

    Model the extent of urban development in Weija-Gbawe Municipality.

The study will contribute imperative knowledge into the tangible setbacks of geomorphological characteristics and processes confronting individuals, households, communities, institutions and government, especially in the Weija-Gbawe Municipality. The study will also aid in finding sustainable solutions to the recurrent hazards to achieve appropriate environmental and socioeconomic gains that will result in human and national growth. By examining human impact on the landscape and geomorphic influence on urban development, the article contributes to sustainable cities (SDG 11) and living on land (SDG 15). It promotes sustainable interactions between humans and the physical environment, arguing that spatial structures and expansion processes can provide a unique perspective for evaluating urban environments and analysing the effects of human endeavours on geomorphological ecosystems.

2 Literature review

The Concept of Geomorphological Features.

Geomorphological features are manifestations of underlying parent materials, as well as the nature and length of geomorphic processes that formed the linked geomorphic units. Each geomorphic feature is related to a specific land use—urban expansion—either directly or through indirect relationships. Thus, geomorphic characteristics and processes have played an important role in the development of built-up areas [15]. Geomorphological characteristics and processes can either restrain urban growth, dictate and regulate the path of urban expansion, or exacerbate built-up area natural hazards. However, large city location and development are often based on socioeconomic and strategic concerns [11].

2.1 The concept of urban expansion

There is no universally accepted definition of urban expansion. Similarly, urban expansion is widely used interchangeably with urbanization [16]. Expatiating on some of these notions [17] regarded the concept of urban expansion in four complementary areas. These are the quantitative measurement, explanatory model, containment and preparing for orderly urban expansion. Whilst the quantitative measurement and explanatory model of urban expansion are related, the views expounded below or above by [16] on the containment and preparing for orderly urban expansion provide an additional valuable and expanded insight. The containment of urban expansion leads to urban sprawl because of outward expansion in rapid growth in cities [17]. Also, preparing for orderly urban expansion denotes rapid growth in cities accompanied by infrastructural development connecting the urban periphery (Keil and Wu. 2022, cited in [17]. The above examples demonstrate that urban expansion refers to an increase in built-up settlement areas, which is frequently accompanied by an increase in urban population size or development in cities. However, growth in urban areas can occur without expansion in contexts of increasing habitation concentration; conversely, urban expansion can occur without urban growth in contexts of de-densification or sub-urbanization. Growth and urbanisation are frequently associated, but not always. For example, a country's urban population can expand in absolute numbers while remaining unchanged in relative terms [16]. Urbanisation and urban expansion are important spatial-social processes that influence human societies and the link between social, economic, physical, and environmental factors [18].

2.2 Interplay of geomorphology and urban expansion

According to [19], the rate of urban expansion in cities poses direct and indirect reversible implications on geomorphological features. However, the growth and development of cities are primarily expanded following the geomorphological attributes such as topography, hydrology of an area and other morphology conditions. This implies that a change in the geomorphology, per the planning and needs of construction, would gradually alter the topographical terrain, hydrology and morphology. Geomorphological characteristics such as terrain or relief, as well as hydrological conditions, are critical factors in a city's extension, growth, and development. Thus, geomorphological planning policies are fundamental in mitigating the effects of natural hazards and disasters in most metropolitan places. The growing demand for urban land use encourages the emergence of geomorphic dangers and processes connected with diverse geomorphological units in metropolitan centres.

Human interaction with geomorphology greatly influences landscape development in cities. However, increased urbanisation, insufficient infrastructure planning, and unrestrained industrial activity generate a variety of changes and topographical transformations. Urban expansion has significantly changed landscape patterns and land cover areas [15]. Geomorphological attributes such as elevation, geology, soil type, aspects and slope immensely attract humans, thereby altering the topography of a defined geographical region resulting from urban expansion in cities. With the increasing population daily, adopting adequate urban planning to achieve long-term environmental stability in a region has become unavoidable. Mohapatra et al. [15] opined that urban expansion and urbanization are incomplete without considering a region's geomorphology and morphological characteristics. Therefore, there is a need to understand the dynamic interactions between different aspects of urban expansion as built-up areas influence geomorphological features.

Similarly, the activities of geomorphological traits that result from urban development significantly alter morphology and landscape dynamics. These attributing traits affect the occurrence of environmental hazards, including earthquakes, vulcanicity, flooding, tsunami, landslide and rockfall or debris materials [15]. Concisely, city expansion and construction activities progressively affect the terrain of cities over time. These modifications have an impact on the rate of geomorphic processes like weathering and erosion.

The expansion of urban areas results in a rising impervious landscape and the expansion of engineered sewage systems, which significantly alter the quantity, paths, and timing of runoff [20]. Changes in the urban landscape also have an impact on hydrological response at different scales. Conventional study has concentrated on the watershed scale sensitivity to changes in land-use covering through a lumped approach, with the goal of determining the influence of increasing impervious surfaces on rainfall runoff and water quality dynamics [21]. There has been little research on how various levels of urbanisation affect ecological sustainability. The consequences of the urban setting occur in small sizes, where elements like buildings (including their density and structure), paved areas, and synthetic connectivity are little known [22]. Jankowfsky et al. [20] investigated the impact of urban infrastructure, such as sewer overflow devices and drainage and sewer networks, on multiple flow features and flow regimes across months and years. The authors [20] discovered that long-term monitoring of sub-catchments was beneficial in providing insightful data on the influence of urbanisation on the observed catchment.

2.3 Thematic mapping of geomorphological impacts on urban expansion

Land use and land cover (LULC) change dynamics have consequences for peri-urban land use and environmental management and planning [23]. In increasing cities, land becomes a 'supportive environment' for infrastructure provision, and urban planning arises through a sequence of crises and social responses to them [24]. Considering this, predicting human land use and land cover (LULC) change is critical for analysing the environmental and social repercussions of human behaviour. The interplay of anthropogenic and biophysical variables causes land-use change, including forest degradation and urbanisation [25]. The underlying causes of land use land cover change (LULCC) differ, and their ever-changing interconnections result in a wide range of change cycles and pathways, depending on the specific environmental, social, political, and historical circumstances in which they emerge [26]. Because of the cumulative impact of driving factors, the human–environment connection fluctuates in both space and time. LULCC causes are classified as either natural or anthropogenic. Human-induced changes in land cover or urban expansion, on the other hand, occur faster than naturally occurring geomorphic processes [27]. This means that human interactions with land usage have a considerable impact on the geomorphological attributes of settlements. The earth's surface is changing in reaction to human demands.

2.4 Theoretical perspectives

The researchers adapted System Analysis and Boserupian Population Theory. System analysis is a methodological framework for investigating the structure and functions of a system. Every system comprises essential aspects such as structure, function and development [28, 29]. Even though reality is infinitely complex in establishing links between variables, system analysis provides convenience in abstracting complexity in forms, which could maintain significant connections to do analysis [30]. In addition, the system concept possibly helps to create closed systems imposing artificial boundaries through experimentation [28, 29]. The system analysis theory describes how the components (input, processing, output and feedback) interact to yield impacts. Thus, urban land use as a sub-system (information and processing) affects or influences the reversible geomorphological characteristics (elevation, slope, aspect, geology, soil and hydrology) and urban expansion. Therefore, the study characterizes the geomorphological features (inputs) in topography and hydrology. Also, the Boserupian population theory denotes how the human population, with advanced technology, impacts geomorphological features and urban expansion in most cities.

2.5 Conceptual framework

The paper is guided by the conceptual framework below. The framework sought to explain the connection between various human and geomorphic factors and their role in influencing each other. The system concept was used in the study to investigate the problem and the effects of geomorphological factors on urban expansion. According to [31], land contains ecosystems, and urban land use is one of the more methodical applications of human interventions to the important parts of any ecosystem to extract value from it. Tivy [32] defines a system as a complicated whole, a set of interrelated components, or an organised group composed of physical objects. The system concept is used to provide a descriptive context and provide balance in nature. Also, the system concept helps in providing accurate analysis of complex systems. Again, the system notion is associated mostly with positivism and functionalism and has been used in a variety of environmental disciplines such as geomorphology, hydrology, ecology, and agriculture. Changes in any of the components have an impact on the core system. As a result, the study investigates the effects of changes in geomorphological characteristics and the macro-environment as sub-systems influencing the area's urban land use system. The conceptual framework of geomorphological impact on urban expansion is depicted in Fig. 1. This section describes the framework under which the study is organised, as well as how the components are integrated as a system. From Fig. 1, the interconnectivity of the variables in both the urban land use sub-system and the geomorphological setting as a system could be seen. Notable variables influencing the urban land sub-system are global population, land tenure system, government policies, technological development, industrialization and economic growth. These variables do not stand on their own as they result in eventualities. Change in global population leads to global externalities such as changes in land tenure system and government policies, leading to the development of technologies to alter the structures in the environment to provide functions and services; hence, industrialization and economic growth will be achieved. When this happens, humans exert pressure on the environment, thereby influencing the geomorphological setting in the area. Also, from the diagram, topography and drainage are the predominant variables in every geomorphological setting and environment. The significant components of topography are elevation, slope, aspect, geology and or soil. When topography and drainage are altered, it brings repercussions on balance in the earth system. It may result in geomorphological hazards such as earthquakes, flooding, landslides, soil creeping, and mudflow, among other hazards.

Fig. 1
figure 1

Source: Adapted from Vink [31]

Conceptual framework of geomorphological impact on urban expansion.

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3 Materials and methods

3.1 Study area

Weija Gbawe Municipality is one of Ghana's 261 Metropolitan, Municipal, and District Assemblies (MMDAs) and one of 29 MMDAs in the Greater Accra Region. The Weija Gbawe Municipal Assembly was formed from the Ga South Municipal Assembly as part of the 2018 district assembly reformation, making it one of 38 newly formed and revised district assemblies. The Municipality is situated in proximity to various surrounding districts. To the north lies Ga South Municipal, to the east is Ga Central Municipal, and to the southeast is Ablekuma North Municipal. Furthermore, the Municipality neighbours Ga South Municipality to the southwest and the Gulf of Guinea to the south. The Municipality is situated in the Southwestern part of Accra. The Weija Gbawe Municipality is positioned between Latitudes 5°47′30"N and 5°27′30"N and Longitudes 0°31′30"W and 0°16′30"W. It spans an approximate land area of 502.31km2 and encompasses around 120 settlements. The study area is the operational area covered by Weija-Gbawe Municipality in Ghana. The operational zone covers the entire region of Greater Accra in Ghana. The Weija Gbawe Municipal Assembly population amounts to 213,674, with a population density of 3,969/km2 and an annual population change of 1.0%. Out of the total population of 213,674, representing 100%, 104,910, representing 49.1%, are males and 108,764, meaning 50.9% are females. However, 139,746, representing 65.4%, are within the active labour force, and 6,783, representing 3.2%, are passively engaged in economic activities [10]. This implies that almost 70% of the population will likely be involved in urban expansion.

According to [33], the Weija Catchment is located in the Densu River Basin's Western Plain. The landscape is low and undulating, with a base elevation of roughly 67 m above sea level (m asl) and several steep, low hills ranging from 300 to 567 m (Fig. 2). The area lies in the dry equatorial climate zone characterised by prevailing high temperatures. The mean annual temperature is about 28 °C. The vegetation includes coastal savanna, transitional zone, strands and mangroves [34]. The geology of the study region comprises the Togo structural unit, which consists of metamorphosed arenaceous and argillaceous sedimentary layers made up of quartzite and micaceous schist. These rocks are highly folded, jointed and fractured, providing favourable groundwater accumulation conditions. Soil types in the study area are savannah schools and savannah lithosols [35]. The ridges often run parallel to the northeast-trending regional structures, and their western slopes are typically steeper than their eastern slopes. The Weija basin region covers a total surface of approximately 1183.167 km2, with wetlands covering 176.325 km2 (14.9%) of the land. The main reservoir within the Municipality is the Weija dam, which experienced breach and destruction due to floods in 1968. Subsequently, the construction of a new dam at the exact location began in 1974 and concluded in 1978 [33]. With an average water level of 14.33 m, the reservoir extends over 29 square kilometres, encompassing a storage capacity of 113.5 million cubic meters (25,000 million gallons) [33]. The reservoir has a total storage capacity of 143.115 million cubic meters (31,803 million gallons), with a maximum intended water level of 15.25 m. According to estimates, inflows into the reservoir might reach 315 000 m3 per day (70 MGD), whereas upstream usage was predicted to be at 40 500 m3 per day (10 MGD) [33]. On environmental issues, the Municipality has several organisations with complementing and competing functions in disaster management, given that it is situated in an earthquake-prone location in Ghana. Compliance and collaboration are key issues amongst these organisations with a thorough framework, but they impede power dynamics, knowledge management, institutional competence, and information sharing. Furthermore, the political participation of NADMO, the main agency, was identified as a hindrance to effective disaster management agency collaboration. Concerning environmental issues, inhabitants on the high slopes faced difficulties in waste collection and access to potable water because supplying water to those regions was costly. Another issue is occasional sediment deposition, which frequently plugs the main road and renders it impassable. These are all urban environmental challenges.

Fig. 2
figure 2

Study area in the regional and national context

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3.2 Research design and sources of data

The anthropo-geomorphology and urban growth of the Weija Gbawe Municipality in Ghana were evaluated using a quantitative technique and a cross-sectional survey design. The survey approach was adopted in response to [36], who argue that the survey design gives a quantitative picture of the population's trends and attitudes by evaluating a sample of that group. According to [37], employing a cross-sectional design facilitates the simultaneous data collection of multiple cases at a specific time, enabling the exploration of relationships between two or more variables. The researcher does not influence or modify the study setting with a cross-sectional design. Employing cross-sectional design allows for making more precise distinctions between cases while evaluating correlations between variables. Additionally, a cross-sectional design offers a structured and consistent methodology to assess and quantify issue variations [37].

Both primary and secondary data were employed in the study. The preliminary data was obtained through the administration of questionnaires. The survey received data from participants regarding their demographic characteristics, the impact of geomorphological features on urban expansion and the human effects on geomorphological features. The secondary data were satellite images (Landsat images) of the study area utilised to model the changes in land use and land cover within the Municipality. The study used periodic Landsat data for 1990, 2000 and 2020 acquired from the USGS Earth Explorer platform (https://earthexplorer.usgs.gov/). Field Observation and Google Earth Pro were used in sourcing and obtaining photos. The study used face-to-face questionnaire administration to deliver a self-constructed questionnaire comprising closed-ended items reflecting the issue under discussion. Before participating in the survey, all respondents provided verbal informed consent. The University of Education, Winneba's Ethical Review Board granted ethical permission for the study's use of human participants.

3.3 Sampling techniques and sample determination

The cluster sampling technique was used in this study. This involves two guidelines; the first criteria involved choosing the study communities, while the second involved picking the respondents. Regarding the study communities' passage, urban areas were taken into account. The Weija-Gbawe Municipal was divided into two clusters, one of which had a more significant proportion of built-up areas and the other a lesser proportion. In each of the clustered regions, all urban areas were categorised independently. The four urban communities were chosen using a simple random selection procedure. The communities' names were written on paper, placed in various boxes, and then hand-picked randomly from the boxes. Simple random sampling is helpful since there is no room for human bias during selection [37]. The second factor considered in the survey's methodology was selecting participants. A systematic sampling approach was employed to aid in accomplishing the study objectives. The sample proportion was computed by dividing the total number of households in each community by the sample size in each district. The initial home was purposefully chosen, and each subsequent home was then identified using the appropriate sample fractions of neighbourhoods. However, it should be emphasised that in certain areas, it was challenging to adhere strictly to the sample fraction when determining the houses due to the disorganised arrangement of the locations. The researchers used meaningful distance while choosing the following household in such cases.

The survey's target respondents were household heads, but when absent, the researchers surveyed any household member above 18 years old. The household served as the analysis unit for the questionnaire survey. In this line, the sample population for the 2020 population and housing census was the total number of dwellings in the Weija-Gbawe Municipality. There are 228,431 households in the Municipality [38]. The sample size was determined using the [39] calculation formula. The procedure for determining the sample size for the study is illustrated below. The household unit served as the analysis unit for the data. Hence, the sample population for the study was derived from the total number of households in the municipality rather than being based on the Municipality's total population. The research identified household dynamics regarding the impacts of geomorphological features on urban expansion.

$${\text{Cap}}S = \frac{{X^{2} NP(1 - P)}}{{d^{2} \left( {N - 1} \right) + X^{2} P(P - 1)}}$$

where:

S = Required Sample Size.

X2 = confidence level (which is 3.841).

N = Population Size (Total number of households which is 228,431).

P = Population proportion (assumed to be 0.50 since this would be the highest sample).

d = Degree of accuracy expressed as a proportion (0.05).

The sample size is therefore calculated as follows:

$$S=\frac{3.841 \times 228431 \times 0.5(1-0.5)}{{0.05}^{2} \left(228431-1\right)+3.841\times 0.5(0.5-1)}$$

S = 385.

The study used 385 households as its sample size.

3.4 Instrumentation and validity

The study's research instrument was a questionnaire with three sections (ABC). The instruments were open-ended in nature, with the first section focusing on the socio-demographic attributes of the participants. The second and third sections solicit responses on the geomorphological impact on urban expansion and human impact on the geomorphological landscape of the Municipality. The surveys were created using the criteria from the literature research and expert discussion. The questionnaires were then delivered to the respondents in order to determine the level of agreement for each criterion. To complete the questionnaires for this study, several processes were followed, including determining the survey's objectives, developing the questionnaire, administering the questionnaire, and evaluating the results. Section A of the questionnaire dealt with demographics, whereas Sections B and C dealt with the key issues of human and geomorphological consequences. To verify that the questionnaires were completed manually, 351 respondents were given them. These questionnaires were provided to study participants who live in the study area. Three hundred fifty-one individuals were reached from the two clusters to offer comments and reasons for the data analysis. The questionnaires were distributed by hand, and observations of the terrain were done to validate the satellite photos. To ensure the reliability of the instruments, a four-member research group consisting of four men was formed to determine the reliability of the research instruments before the actual fieldwork was conducted. The research instruments were peer-reviewed. In addition, the digital elevation model (DEM) was downloaded from earthexplorer.usgs.gov see (Table 1). Following processing for sinks and fills using ArcMap 10.8, elevation was clipped to the study area using the Shuttle Radar Topography Mission (SRTM) dataset, as shown in Fig. 3a, b, respectively. The elevation data was further used to process the slope of the area. All datasets were trimmed to fit the study area's border and projected from GCS WGS 1984 to Ghana Metre Grid. The provision of a digital elevation model (DEM), a full digital depiction of the elevation of the Earth's surface, is a key accomplishment of the SRTM therefore its application in the study. Due to its exceptional quality across all domains, this dataset provides several advantages. Furthermore, it is inexpensively available and straightforward to obtain.

Table 1 Landsat images.
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Fig. 3
figure 3

Source: Fieldwork, (2023)

a The elevation map of Weija Gbawe Municipality in meters. b Slope map of Weija Gbawe Municipality in degrees.

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3.5 Data integration processing and analysis

Periodic Landsat images between 1990 and 2020, aerial photographs, and topographic maps were integrated into GIS Software. ArcMap, EDARS Imagine, and Google Earth Pro were utilised for processing the images. Based on the study's objectives, the data was analysed. The first and second objectives were subjected to quantitative analysis using SPSS software, specifically version 26. Because of its considerable statistical capabilities, SPSS version 26 was used. It is a unique program that can produce attributes from data already stored [40]. The programme includes automatic algorithms for detecting anomalies as well as statistical adjustments to address any outliers [41]. The use of SPSS software allows us to run statistical analyses for meta-analysis on the data obtained and evaluate the results. The survey questionnaire was encoded and inputted into the SPSS software for further investigation and presented using descriptive table frequency. Objective three was analysed using the Municipality's land use and land cover change data from 1990 to 2020. The results were further represented using charts, graphs, tables and maps.

The RII method was used for data analysis. In this study, relative index analysis was used to rank the criteria based on their relative importance. The relative index is calculated using the following formula: RII = ∑W/A x N, where W is the weighting assigned by respondents to each element, N is the total number of respondents, ∑ is the total frequency in the sample, and A is the highest weight.

3.6 Accuracy assessment

In order to maintain the accuracy of image classification, each LU dynamic identification follows a precise procedure. This entails utilizing Google Earth Pro and Sentinel 10 m satellite imagery from three distinct years, obtaining 25 training samples for each category. The precision of the outcomes is then evaluated for each sample. Additionally, a ground control point is validated for each year through the utilization of Google Earth Pro's historical imaging capabilities. To ensure accurate classification, each point in the sample image underwent double-verification against the ground truth. This involved checking if the point corresponded with the same land use class in the Google Earth Pro images. The level of agreement between the findings and the actual circumstances was assessed using the Kappa coefficient (K). An accuracy of at least 0.75 Kappa coefficient was considered acceptable. To establish 25 points for each class annually, 525 Ground Control Points (GCPs) were used as ground truth sites. The Kappa coefficient was calculated using the equation provided by [42].

$$K\, = \,\frac{{N\sum\nolimits_{i\, = \,1}^{k} {x_{ii} \, - \,\sum\nolimits_{i\, = \,1}^{k} {\left( {x_{i + } \, \times \,x_{ + i} } \right)} } }}{{N^{2} \, - \,\sum\nolimits_{i\, = \,1}^{k} {\left( {x_{i + } \, \times \,x_{ + i} } \right)} }}$$

To provide a clearer understanding, the equation explains the following notations used in this context:

  • 'k' represents the total number of rows in the matrix.

  • 'xii' signifies the number of observations that are shared by both row 'i' and column 'i.'

  • 'xi + ' denotes the total number of observations along row 'k.'

  • 'x + i' denotes the total number of observations along column 'i.'

  • 'N' stands for the total number of observations.

3.7 Ethical consideration

Confidentiality and the protection of participant interests constituted the primary ethical concerns in this study. The researcher maintained a neutral position in the survey to prevent bias by demonstrating and upholding high standards of integrity and professionalism. They also ensured strict confidentiality when accessing information related to the study. The researcher kindly asked the respondents to allocate some time from their busy schedules to complete the questionnaire, assuring them of complete confidentiality to alleviate any concerns or apprehensions during the response process. An introduction letter was obtained from the School of Graduate Studies, Department of Geography, University of Education, Winneba. The community's stakeholders were also asked for permission, which provided additional assurances to the respondents about anonymity and that the material would only be used for research reasons. As a result, the researcher carried out the research effectively, fostering a greater sense of honesty among the respondents. The researchers strictly utilised the collected data solely for its intended purpose.

3.8 Limitations of the study

The study is limited by scope and methods; the research concentrated at Weija Gbawe municipality, one of the fast-rising areas in the Greater Accra region, Ghana. By scope, the paper could have prioritised to some of the equally critical metropolitan areas in Ghana but only concentrated on the Weija Gbawe Municipality. The improper layout of the dwellings in the neighbourhood made it difficult to identify the residences purely based on the sample fraction. In such circumstances, the researchers chose the next family based on meaningful distance. Household heads were targeted as survey respondents, but in cases where they were not present, a surrogate adult household member over the age of 18 was surveyed. Despite this constraint, the study's findings are still legitimate, regardless of the limitations that posed a threat. Future research could include a comparative examination of several urban areas in the Greater Accra region. Such a study should take into account the institutions tasked with overseeing urban planning matters as well as assessing the relationship between humans and geomorphological issues. Cities and communities in the global south and Africa are likely to gain significantly from the methods and outcomes of this study.

4 Results and discussion

4.1 Demographic characteristics of respondents

The research solicits information from three hundred and fifty-one (351) out of three hundred and eighty-five (385) targeted respondents due to incomplete responses. The demographic data analysed were gender, age, type of building structure, and ownership rights. Table 2 depicts the findings from the survey. The results reveal that 59.0% (208) of the respondents are male, and only 41.0% (143) are females. This study shows gender inequality through male domination in household headship. With age, the analysis shows that 3.0% (10) of the survey respondents are less than 20 years, 26% (91) of the respondents are between 21 and 40 years, 52.0% (182) of the participants are between 41 and 60 years, and only 19.0% (68) of respondents are more than 61 years of age respectively. This ascertains that most respondents fall between 41 and 60 years, which defines the level of urban geomorphology interactions depicted in Table 2 below. Regarding ownership and the type of building structures, the results reveal that most respondents, accounting for 56% (195), are owners of the constructed buildings. Conversely, a minority of participants, representing only 44% (156), do not own the built-up systems within the catchment areas. Regarding the type of built-up structure, the findings from the study revealed that 32% (113) of the respondents lived in compound structures. This is followed by apartments, which account for 31% (109) and 29% (192) of Self-containment, respectively, with only 8% residing in other established complexes. This section describes how the ownership rate and types of built-up systems alter the magnitude of geomorphological features resulting from urban expansion in Weija Gbawe Municipality.

Table 2 Bio-data of respondents.
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4.2 Human impacts on geomorphological features in the study area

It is common knowledge that anthropogenic activities in most urban areas dramatically affect the geomorphological characteristics (topography and hydrology) resulting from urban expansion, affirmed by [6, 27, 43]. Based on the formula for computing RII, the W for this phase they are ranged from 1 to 3. The Relative Importance Index (RII) analysis indicates that population growth (0.89) and industrialisation (0.72) with their corresponding mean and standard deviations of (4.47 and 0.66) for population growth and (3.58 and 0.8) for industrialization, respectively, as the first two top anthropogenic characteristics that impact geomorphological features (topography and hydrology). The results have been presented in Table 3 and imply that a rapid increase in residents and industrialisation from urban expansion significantly affects any defined geographical region's geomorphological features (topography and hydrology). This is an indication of an ever-growing population, as was supported by the national population census's annual rate of change. The other variable, economic growth, has a direct relationship with industrialization and was also recorded at 0.68 with a mean of 3.41. It was ranked the third most important factor, with government policies being the least ranked. The tendency of industrialization to promote economic growth is rife and has been recorded in many places. The rank of government policies, 0.49 with a mean of 2.46, is in the right direction. Land acquisition and usage are most often determined by individuals with limited control from the government and its agencies. It was noted by field investigation how the topography of the area is carved into or modified to allow the construction of buildings for industrial and domestic usage. This, in effect, usually causes debris avalanches during torrential rainfall, resulting in a blockade of roads and the destruction of lives and properties [44]. According to [45], humans are the most essential driving forces (they determine more than half of the outcomes). However, "overwhelming" may be more prevalent (at least 95% of products are distinguished by it) in landscape changes and accordingly, humans are the primary agents of geomorphic alteration. Anthropogenic landscape change will likely be much faster than expected from natural geologic processes [46].

Table 3 Human impacts on geomorphological characteristics.
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According to [47], human activity has been acknowledged as a major influencer of geomorphic processes. The authors argued about the potential for agriculture to hasten soil erosion. Borrelli et al. [48] highlighted the impact of dams and reservoirs on the uninterrupted sediment movement in river systems. Poeppl et al. [49], who aver that the construction of road networks correlates with the stability of road cuts and other geological hazards, as discussed by [50], support this observation. The findings by [51] show that anthropogenic activities include housing and infrastructure development, tillage and crop cultivation, stream mining, deforestation, livestock grazing, and garbage disposal on the channel bed. Removal of forests and a high proportion of sandy-to-sandy loam soil texture have exposed soil to a variety of processes that lead to erosion. This has ultimately led to the deformation of channel banks through various geomorphic processes. Since the advent of early urbanisation, humans have dominated the geomorphic forces that shape the environment and influence how we conduct our daily lives [52]. Hooke [53] avers that human activity is the most crucial geomorphic force shaping the earth's surface.

Similarly, for thousands of years, human societies have been reshaping the geomorphology of landscapes, creating human-caused geomorphic features such as earthworks and reservoirs as well as settlements, roads, canals, ditches, and plough furrows that differ from landforms created by natural processes. Tropical ecosystems have had human influence over a long period in the form of customary land usage, which takes many different forms [54]. However, compared to the thousands of years of human activity, swift population growth and technological advancements in the previous century have significantly increased human impact on physical ecosystems. The primary human actions that transformed the urban environment of the study area include diversions in riverbeds and channelisation, digging, filling, and embankment building along the shore [55].

Table 4 illustrates the population dynamics of the Weija Gbawe municipality. Information on population dynamics is needed to support the incidence of urbanisation and its ramifications on the landscape. The total area, which is static, is 284.08 sq km. Based on the 2010 population data of the Municipality, it had a total population of 191,623. The population almost doubled recording 314, 299 based on the 2021 national population census. The annual population change between 2010 and 2021 is 1.0 per cent. Furthermore, with 3,969/km2 as the population density. Considering the rate of increase and the available land, the alarming rate of population change (increase) and considering the land use analysis in the area. The restricted based on the land use land cover analysis showed the built-up area as the dominant land use for building houses and industrial use. This, by implication, corresponds with the recent land-guards and land litigations in the area. Different land uses, therefore making land acquisition challenging, are competing for the limited land. Population growth is critical to urban expansion as the Municipality is an urban enclave. Peng, Liu, Zhang and Li [56] assert that linkages between urban population density distribution and land utilisation are critical to developing the spatial organisation of cities.

Table 4 Population trends of the Weija Gbawe Municipality.
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4.3 Geomorphological impacts on urban expansion

The Relative Important Index (RII) was also used to investigate how geomorphological factors influenced urban expansion. For this phase, W ranged from 1 to 5. As shown in Table 5, the data analysis findings revealed that slope and elevation are the first topographical characteristics affecting urban growth in Weija-Gbawe, with an RII of 0.84 and 0.83, and means and standard deviations of (4.21, 0.81 for slope, 4.14, and 0.99) for elevation respectively. Hydrology, with an RII of 0.66, was ranked the fourth geomorphic feature affecting urban development. By implication, most settlements within the metropolitan area are found in gentle sloping or flat terrain. This, in a way, has direct consequences on the availability and access to land in the catchment area. This means elevation and slope serve as a constraint to urban expansion within the Weija Gbawe metropolitan area. The area is also floodable as torrential rains in the area inundate and make many communities inaccessible, making the hydrology another significant variable to urbanisation in the area. The recent development of housing on the steep slopes has become common among some well-to-do populace, and these come with their challenges, such as climbing the hills to access the land, siltation, and difficulty in connecting social amenities such as potable water, roads, electricity, etc. This result sided with a similar study that reveals that slope is a barrier to the urbanisation of cities and that urban expansion happens primarily in places of low elevation [57]. This finding suggests a positive correlation between the growth of Weija-Gbawe and the terrain. Weija-Gbawe's evolution was primarily confined to flat ground, and the elevation and slope substantially hindered the city's development. However, developers have attempted to occupy the high settings, contributing to sand and mudflow during rainfall. The inappropriateness of mountainous regions as urban expansion areas can be attributed to limestone formations, varied slopes, altitudes, primary and secondary faults, and the activation of geological processes [58]. Daoudi and Niang’s [11] research emphasises the interplay between geomorphological features and the urban expansion of Jeddah, Saudi Arabia's largest metropolis, leading to the formation of biodiversity-related dangers. Their findings show that from roughly 36 square kilometres in 1965 to more than 1,130 square kilometres in 2020, the urban area expanded more than 30 times and more than doubled. The town's expansion encompassed various morphological segments, increasing vulnerability and exposure to multiple hazards. Another study by Kanga, Singh, Meraj, Kumar, Parveen, Kranjčić, and Đurin [59] noted that hills in the area had decreased due to their conversion into industrial and built-up areas. Similar studies by [60] found that urban expansion and diversity of human activities in the Russeifa district resulted in a change in the features of the region, both topographically and geomorphologically, in the form of altitudes, elevation and slopes. According to [61], the interaction of hydrologic and geomorphic elements, such as rainfall, temperature, altitude, gradient, and distance to the river network and shoreline, as well as connectivity to urban centres, is recognised as an important source of urban evolution. The results and research by other scholars highlight that anthropogenic land covers and landscapes can be identified by examining the distribution of geomorphometric indices and their impact on each other. In this case, geomorphic indices such as slope, aspects, topography, hydrology, and geology of an area are determining factors of urbanisation growth in a given geographical location.

Table 5 Geomorphological impacts on Urban expansion.
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4.3.1 Digital elevation model of the Weija Gbawe Municipality

Figure 3a depicts the elevation map of the Weija Gbawe Municipality, indicating areas with the highest and lowest altitudes. The highest elevation from the DEM data is 194 m, with −3 m being the lowest. Most parts of the southern section of the area have the lowest elevation, and the highest elevation is recorded in the northern part of the Municipality. The data shows that urban expansion is concentrated at the medium to the lowest elevation, where the land is more accessible to the people. The core area, primarily medium to low elevation, was found to be concentrated by the residents, with elevation between 17 and 138 m. The region's built-up areas increased significantly, with rapid expansion in the core area. The conclusions are congruent with those of [62] on the geospatial analysis of urban expansion utilising remote sensing methods and data: a case study of the Yangtze River. Although recognising that elevation is a key determinant in urban development, the investigation revealed that people are still residing in high places. According to Shi, Cui, Liu, and Wu's [63] research, worldwide urban land evolution follows a slope-climbing technique with remotely sensed nighttime light. Their global average slope of urban entities climbed from 0.85° in 2000 to 0.96° in 2020, a 0.11° rise encompassing Asia, Africa, and South America.

4.3.2 Slope of the Weija Gbawe Municipality

Determining the inclination of a slope requires calculating the angle of the slope, which ranges between 0 and 90 degrees. In addition, the inclination can also be expressed as a percentage value, ranging from 0 to infinity. A level surface has a percentage rise of 0, while a surface with a 45-degree angle has a 100 percent rise. As the slope becomes steeper, the percentage rise increases proportionally. The results from the slope map indicate that (Fig. 3b) population concentration was found at the central portion of the Municipality with contour ranges of 2.4–6.8°. These areas are the gently sloping areas or flat topography, and high concentrations were expected. The low-lying areas 0–2.4° degree, which were closer to water bodies, were also moderately settled. It is considered the typical zone where the original Weija Gbawe indigenes area is found. Areas with 14.7–33.4°and 6.8–14.7° are steep slopes and are susceptible areas with limited population concentration. By implication, these are the high-rise areas with wealthy (rich) inhabitants residing in these areas. These areas are highly susceptible to slope failure, leading to erosion and mass wasting. According to Atakorah, Owusu and Adu-Boahen [1], anthropogenic factors such as urbanisation, industrialisation, and population growth have contributed to urban sprawl in low-elevation areas in Ghana, making such areas highly susceptible to floods due to alteration in the landscape. Zhang, Zhao, Ren, Hai, Guo, Li, and Gao [64] perceive that population and GDP are the most influential elements controlling the slope-climbing phenomena of urban construction land. In contrast, natural circumstances are the most significant variables influencing other construction land. They opined that slope is an important factor that influences urban expansion. Atakorah, Owusu and Adu-Boahen [1] observed in their study that slope is a vital factor in urban development. They contend that most settlements are found in low-lying and gently sloping areas at the expense of high elevations.

4.4 The extent of urban expansion in Weija Gbawe

Land-use change is produced by an interaction of anthropogenic and biophysical processes, notably urbanisation and deforestation of forests, according to [65]. Similarly, this study further models the prospective impacts of global population expansion, resulting in urban growth for thirty (30) years using GIS and Remote Sensing applications. This was necessary because the extent of urban development needs to be scientifically measured to determine the rate of land use and land cover change (LULCC) concerning research conducted by [10]. Tables 6 and 7 illustrate land use land cover dynamics in the study area.

Table 6 Land use and land cover classification scheme.
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Table 7 Land use and land cover distribution.
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Land use and land cover changes (LULC) between 1990, 2000 and 2020 were classified using Landsat images. The LULC categories were classified as closed forest, open forest, waterbody, salt pond, built-up area, and bare area. Some land use classes recorded significant changes, while others had slight changes (Figs. 4, 5, 6 and 7). Built-up was the dominant land use practice in the municipality, which is an indication of the increasing population and demand for settlement and industrial establishment that requires huge land for such ventures.

Fig. 4
figure 4

Source: Author's Construct, (2022)

Land use land cover 1990.

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Fig. 5
figure 5

Source: Author's Construct, (2022)

Land use land cover 2000.

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Fig. 6
figure 6

Source: Author's Construct, (2022)

Land use land cover 2020.

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Fig. 7
figure 7

Source: Author's Construct, (2022)

Changes in other land covers to built-up from 1990 to 2020.

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As shown in Table 7, the trends of LULC from 1990 to 2020 showed that closed forest opened forest, and waterbody declined by 18.3%, 19.8% and 2.3%, respectively, while the built-up and bare areas had an increment in area coverage. A similar study found that the area of bare land, forestland, herbaceous land, and waterbody dropped by 0.05%, 90.52%, 71.67%, and 6.90%, respectively. The research area's LULC changes were linked to urbanisation, population growth, socioeconomic growth, and climate change. The results imply that most arable lands are being lost to urban residential use. The result is a reduction in food supply and exposure of the land to natural events such as flooding. This is because no vegetation cover serves as a barrier as the ground becomes bare and open. It was recorded that the Municipality, due to its proximity to Accra, is receiving the growing population with the need for infrastructure and social amenities to meet the needs of the increasing population. Rana and Sarkar [66] discovered similar results, reporting that changes in land cover directly impact land surface temperature (LST) by modifying the biophysical properties of the land. Changes in land cover, such as the transition from vegetation to impenetrable surfaces like asphalt, rooftops, and blacktops, are the leading cause of LST. This built-up zone, described as urbanisation, converts natural land cover into artificial structures, including houses, commercial buildings, and transport networks [67, 68]. In 1990 and 2000, built-up was 5.7% and 13.4% of the classes, respectively. The percentage of built-up areas experienced a significant rise, increasing from 5.7% in 1990 to 40.3% in 2020. Rapid urbanisation and population growth are the driving forces for incrementing the urbanised area. This increment moved hand in hand with population growth. In addition, the increasing demand for residential areas due to rapid urban expansion can be accounted for the decline in the vegetative regions of the Municipality. The findings are congruent with the findings of [69], who discovered that settlement and other land use increased from 2.68% to 16.46% in 1987 to 3.65% and 53.47% in 2003, and eventually to 20.61% and 58.52% in 2017. The findings based on the indicated years' land use types portray that the Municipality is undergoing fast urban growth. This result sided with a similar study that confirms that human activities associated with land use directly influence the composition of land cover. Rising populations, settlement growth, and increased use of land resources for economic growth all contribute to this [14].

Indications from Figs. 4, 5, 6, and 7 statistically imply that LULC changes over time due to rapid population growth coupled with urban expansion (built-up structures) influence geomorphological characteristics such as terrain, topography, and hydrology. The geomorphological elements like slope, elevation and hydrology affect the landscape of a defined geographical region. The impact of the growing population on the geomorphic nature of the area is that humans alter the equilibrium between nature, and most of the consequences are negative. The negative results of human impact on the landscape could be seen from deforestation, pollution, poor waste management practices, extinction of species and deformation of the landscape. These also trigger natural events such as flooding, urban heat, etc.

The dynamics in the urban landscape, coupled with rapid population growth, dramatically influence the physical morphology in the geographical setting. Similarly, the hydrology level changes with specific evidence of water level declining from 17.0% in 1990 to 14.7% in 2020, respectively, concerning population growth over time, as denoted in (Table 7). This result aligns with a similar study that indicates that human actions extending from cultivation to urban land use have considerably affected semi-urban areas. Analysing changes in land use and land cover is vital for understanding the relationships between the factors driving land use change and its resulting impacts [23, 24].

Theoretically, the study manifests in a way that combines the human and geomorphologic factors and how each shapes the other. The System Analysis and Boserupian Population Theory sit well with the study as the variables such as elevation, slope, aspect, geology, soil and hydrology, which are geomorphic, interact with the human, in this case, population leading to urbanisation and determine the concentration or otherwise of the populace over a given geographical area. Urban expansion in Weija Gbawe is determined by the interaction between humans and the environment as envisaged by the theories that underpin the study.

5 Conclusions

The findings have demonstrated that population growth is a significant human factor in the Weija Gbawe catchment that alters geomorphology and urban expansion. Population size increases positively and changes an area's landscape resulting from urban development. Records obtained from 2010 and 2021 Ghana’s population census showed an annual rate of change of 1.0 per cent. The analysis showed almost double the population of the Municipality when the 2010 and 2021 population figures are compared. This, by implication, means the need for more space to respond to the increasing population. Another implication is the need for the government to provide basic amenities such as schools, hospitals, markets, roads, etc., to meet the growing needs of the populace. Similarly, the topographical terrain, like slope and elevation, were the most predominant geomorphological characteristics modifying urban expansion in a defined geographical setting. Urban agglomeration was discovered to be concentrated in the low-lying areas, with some establishments in the high-rising areas. The settlements on the high gradients were difficult to access and contributed to the deposition of sediments on the major roads linking the capital city, Accra. This implies that the geomorphological features like slope and height in the Municipality influence city or urban development within most catchment areas. Through land use modelling, the study also revealed that within the last three decades, vegetated lands had been transformed into built-up regions from the LULC analysis performed. This is due to anthropogenic activities such as residential, commercial and industrial purposes. The area's proximity to Accra, the capital of Ghana and the substantial demand for land has resulted in the expansion of the Municipality. However, the extensive urban land use in Weija Gbawe Municipality is characterised by built-up infrastructure and industrialisation. This, by implication, alludes to the overconcentration of the population and other national and international offices in the central business district (CBD) of Accra and the subsequent huge traffic, making travelling to the city centre a very difficult task. The research indicates that using geographic information systems, remote sensing, and field surveys is critical for developing complete knowledge of Anthropocene and urban geomorphology. This is conceivable by utilising GIS and remote sensing to examine changes in land use and land cover in the study region, as well as using the digital elevation model DEM to analyse slope and elevation and their contribution to urban expansion.

6 Policy recommendations

For policy recommendation, the Weija-Gbawe Municipality and the Government must effectively modify, implement, educate, persuade, and enforce the 2010 population policy, which aims to achieve rapid socio-economic growth and development and ensure effective and rational utilisation of the country's resources. This could be done by bridging the weak linkage between land use/road planning and aborting applications received which were not in line with the planning standards and approving those that are accurate and standard. Institutions such as the Environmental Protection Agency (EPA), the Physical Planning Agency (PPA) and the National Disaster Management Organization (NADMO) in the Weija-Gbawe Municipality ought to enact and enforce environmental by-laws that could restrict people from building along slopes, elevations, drainage basins among others in the Municipality. In doing so, the Municipality should work on the existing complex protocols of getting building permits and relax the procedures whilst being firm and straightforward. The by-laws should consider the culture and local knowledge of the people so that the concept of ownership and acceptance would not be a problem. This will encourage prospective builders to conduct due diligence on land acquisition and follow the laid down processes and conventions promulgated by the Municipality with regard to land use practices and planning. Also, individuals, households, agencies, institutions and governments ought to deploy environmental actions such as “Green spaces" "Technogardens and the application of the practical concept of conservation and preservation approaches to losing the entire environment to built-up structures and industrialisation. When that is done, urban green spaces will be created, and the environment with its aesthetic values conserved and sustainable land use ensured.