1. Introduction
HR is defined as the restoration of river systems adversely affected by either human activities or natural occurrences. This involves leveraging historical data on precipitation, temperature, extreme flows, and vegetation cover. The overarching goal is to mitigate the impacts of intensive agriculture, erosion resulting from natural processes, biodiversity loss, and poverty, as well as to address the challenges posed by droughts and floods due to climate change. This is accomplished through the application of morphological analysis, remote-sensing techniques, GIS, and the Analytic Hierarchy Process (AHP). This study’s significance is underscored by its adept integration of numerous variables, its capacity to incorporate the perceptions and preferences of diverse stakeholders into future HR decision-making processes, and its flexibility in adapting to fluctuations in data availability and shifts in watershed conditions [
1,
2,
3,
4].
By implementing the AHP in HR, this research not only provides a robust decision-making framework but also contributes to the scientific literature by providing a practical example of how advanced decision-making techniques can be applied in natural resource management. This may inspire further studies and the adoption of similar methodologies in other disciplines or in other environmental contexts, increasing the relevance and impact of the research. The method proposed in this research proposes the use of the scarce environmental data in developing countries and their HR by adjusting the model for the future with the interested parties (states, NGOs, and local communities). Unlike other HR studies, this research integrates seven morphometric variables (the SPI, TWI, TRI, STI, SD, CN, and RD); two soil texture–vegetation cover variables (the CN and NDVI), and one climatological variable (RF). The hypothesis of this study was as follows: The integration of the GIS and AHP allows for an effective and accurate prioritization of areas requiring HR in the Dulcepamba River watershed. Areas with high soil erosion, low soil moisture, and high runoff demand immediate hydrological restoration interventions.
Hydromorphological assessment methods are essential tools for gaining an in-depth understanding to guide the most appropriate solutions for future restoration projects. The careful management of water resources is a fundamental pillar for ensuring the sustainability of river landscapes and guaranteeing a continuous supply of quality water [
5]. In recent decades, agricultural intensification has resulted in significant soil degradation [
6]. For territorial development planning in the Dulcepamba watershed, it is imperative to investigate HR areas capable of improving both the ecological environment and quality of life of local residents [
7]. Approximately 19,000 inhabitants depend directly on agriculture and livestock; 20% live in the urban area in 20 villages [
8].
The Analytic Hierarchy Process (AHP) emerges as a multicriterion decision analysis approach within the field of geographic information systems (GISs) [
9,
10,
11]. In this context, two approaches to the application of the AHP are distinguished. First, it can be used to determine the weights associated with the layers of the attribute map, which can then be combined in a manner analogous to that of other weighted aggregation methods. This method is particularly useful when the number of alternatives is considerable and it is impractical to compare them. Second, the AHP principle can be used to assign priorities at all levels of the hierarchical structure, including the level representing the alternatives. In specific situations, a relatively small number of alternatives are assessed [
12]. The AHP approach is predominantly used to integrate independent factors to evaluate the soil suitability for irrigation, cultivation, and groundwater recharge [
13,
14,
15]. In addition, this study introduces a new perspective on the AHP based on matrices and the weighted linear combination method, relating to soil erosion hazards and the current climatic conditions, to identify and evaluate ecologically viable agricultural systems [
16].
The report of the Intergovernmental Panel on Climate Change (IPCC) defines land degradation as an adverse trend caused by human activity, manifesting itself as the long-term loss of biological productivity, ecological integrity, and value to society. The United Nations Convention on Combat Desertification (UNCCD), adopted by 195 countries in 1994, recognized this problem as one of the most pressing environmental challenges [
15,
17,
18].
Table 1 shows the soil loss in technologically intensive agricultural fields, which is 18–21 tons/ha/year, in contrast to that in fields tilled by hand, which is 0.8 tons/ha/year. Soil formation in areas without erosion is limited to only 0.05 tons/ha/year. Soil conservation techniques reduce the soil loss to between 0.004 and 0.05 tons per hectare per year, especially in stable forest ecosystems where vegetation protects the soil from erosion [
19]. A total of 26% of the Dulcepamba Basin territory is short-cycle crops cultivated by hand; there is no evidence of technologically intensive agricultural methods [
20].
The urgent need to evaluate HR zones will translate into concrete actions by the Autonomous Decentralized Governments of Chillanes and San Miguel, who will have to implement measures to mitigate the hydrological vulnerability in the Dulcepamba River Basin.
4. Discussion
The following is a discussion of the values of the variables analyzed in the maps in
Figure 5: SPI: Most of the territory is experiencing soil loss, which negatively affects the soil productivity. TWI: The territory is prone to low-humidity conditions, which benefit the erosion risk but limit the water availability to plants. TRI: Areas with higher roughness may be more prone to erosion and mass movement. STI: This index indicates that there is little sediment movement in the watershed, indicating that it is positive for the water quality. SD: Soils with high permeability allow good water infiltration, which reduces surface runoff and erosion. CN: Soils with high runoff are at a higher risk of erosion and should be managed more carefully. RD: A low percentage of susceptibility suggests that most of the territory is not at high risk of fluvial erosion, but affected areas require specific attention. NDVI: A significant proportion of vegetation is stressed, which may be indicative of problems such as lack of water, disease, or unfavorable soil conditions. RF: Areas with lower rainfall are more vulnerable to drought and may have greater challenges in terms of water availability for restoration. The variables causing the spatial patterns in
Figure 7 in order of priority are as follows: the TWI, NC, NDVI, RF, SD, STI, SPI, and TRI.
In the context of topographic indices, the control of soil erosion and sediment transport can be calculated using empirical methods or simple equations, as highlighted in previous studies [
49]. These indices have demonstrated accurate specificity in delineating shallowly saturated zones and in determining the soil water content in our study area [
50,
51,
52]. The results derived from the Topographic Wetness Index (TWI) indicate high reliability for vegetation assessment by accounting for the spatial distribution of the soil moisture, a critical factor in the formation of surface runoff [
53,
54]. The Soil Loss Index (SPI), which estimates the amount of erosion on a slope affected by the surface flow, has emerged as a valuable tool for identifying areas prone to sediment transport and different forms of soil erosion. Consequently, these areas highlight the suitability of afforestation as an effective measure for controlling soil erosion [
49]. In the initial stages of land rehabilitation, priority should be given to local and native pioneer species as part of a sustainable development strategy for natural resource preservation [
7].
To prioritize sub-watersheds according to their potential erosion risk and water availability, we integrated the morphometric parameters, precipitation, NDVI, and soil texture, based on previous investigations [
51,
55,
56]. Topographic features play a crucial role in soil erosion and sediment transport processes by influencing the surface flow [
7,
57]. An analysis of the secondary topographic indices (the TWI, SPI, and STI) was performed to generate a relative susceptibility map for hydrogeomorphological restoration. The most prominent reasons for this environmental susceptibility are steep slopes and sparse vegetation cover [
58].
Climate change affects agricultural production by altering the water availability, soil quality, and nutrient levels [
19]. The threat of soil erosion affects agricultural productivity, ecosystem functionality, and environmental sustainability. This phenomenon leads to a reduction in organic matter and essential nutrients, such as nitrogen, phosphorus, and potassium [
19]. In addition, it affects ecosystem functions and services, including soil formation, hydrological cycling, and soil nutrient cycling [
59], leading to a reduction in biodiversity, water quality, and food security [
60]. The identification and prioritization of critical areas can be used to implement land-use planning and development actions to mitigate the impact of soil erosion [
51,
61,
62].
Table 15 shows that 38% of the soil on the planet is used for agriculture (1850–2011), and several studies suggest that the degraded soil on the planet has reached an average of 27% (1983–2015). According to this study, approximately 33% (130 km
2) of the Dulcepamba watershed and less than 40% of the degraded soil in Bolivar Province (4310 km
2) require high–very high restoration [
8]. According to [
63], agricultural productivity worldwide has decreased by 20% (1999–2013) due to soil degradation.
The Analytical Hierarchy Process (AHP) multicriterion spatial assessment method for assessing land degradation has been widely used in environmental assessments [
70,
71,
72]. Jain Ref. [
70] found efficiency in the calculation of indices and remote-sensing techniques to investigate the relative vulnerability to soil erosion. Several researchers have attempted to assess the crop suitability, susceptibility, and hydrologic health of watersheds using AHP methods [
51,
71,
72]. This study attempts to introduce a new AHP approach based on matrices and the linear and weighted combination method, in relation to soil erosion hazards, runoff, infiltration, and land use, to identify and evaluate ecologically viable agricultural systems [
6,
13,
14,
15,
16].
The AHP effectively integrates variables into a coherent and structured framework, prioritizes restoration actions, can include stakeholder preferences, allows stakeholders to understand how and why certain decisions are made (government, NGOs, and local communities), and can be adjusted according to the data availability, which is limited in developing countries [
6,
73,
74]. This study also contributes to the scientific literature by providing a practical example of how advanced decision-making techniques can be applied in natural resource management.
5. Conclusions and Recommendations
In the rainiest months (March–April), the most affected areas from the hydrological point of view are located in the high–very high HR zones, as shown in
Figure 7. Approximately one-third of the territory of the Dulcepamba watershed exhibits considerable degradation in its hydrological conditions, reaching 33.35%. In contrast, 10.7% of the evaluated area does not require HR intervention, while 20.28% requires this type of action in the long term. In addition, 30.67% requires short-term interventions, and 33.35% requires immediate HR; thus, the hypothesis of this study is fulfilled. To address the HR, the decision makers would be as follows: the Prefecture of Bolivar Province, the Dulcepamba Project [
75], and local communities.
When using the maps, the following is recommended: SPI: Reduce erosion with the intervention of the Prefecture of Bolivar and its Secretariat of Environmental Management and Natural Risks with training programs for environmental monitoring and evaluation. TWI: Construct permeable water retention structures to enhance infiltration. TRI: Prioritize biological restoration in highly rugged areas, using native species. SD: Enhance connectivity within biological ecosystems. CN: Give precedence to reforestation initiatives with native species in regions experiencing high runoff. RD: Establish riparian barriers with indigenous vegetation. NDVI: Utilize drones equipped with multispectral cameras to assess indicators following interventions in high-risk areas. RF: Develop stormwater management systems to prepare for extreme events like floods and droughts.
The professional in charge of the HR strategy must possess a deep understanding of the specific environmental conditions of the location, as well as understand the social and economic requirements of the region [
76]. Achieving HR involves balancing the hydrological, ecological, and agricultural conditions using techniques such as terracing, check dams, and native afforestation [
76]. Transverse ditches filled with gravel and sand can be used to effectively increase soil moisture [
77]. To improve the sustainability of a watershed, it is essential to identify aspects such as the water quantity and quality, species, ecosystems, resilience to climate change, and local culture [
78,
79]. Ecological management aimed at improving the quality of land use involves the transformation of grasslands into forests. The water conservation capacity (WC) of forests per square kilometer exceeds 600 mm, whereas that of grasslands is approximately 192 mm, and arid lands can result in a loss of approximately 300 mm of their WC [
80].