Stormwater Sewerage Masterplan for Flood Control Applied to a University Campus

: Floods generated by rain cause signiﬁcant economic and human losses. The campus of the Escuela Superior Polit é cnica del Litoral (ESPOL) has a drainage system that conducts stormwater to two discharge points outside the campus. The system works effectively at the macro-drainage level. However, a very crowded area is deﬁcient at the micro-drainage level, which has registered ﬂooding and the proliferation of vectors that affect people’s health. This work aimed to design a masterplan for stormwater sewerage by analyzing the existing situation and applying technical criteria that allow the establishment of solutions and strategies to control ﬂoods at the university campus. The methodology consisted of: (i) data collection and processing for the stormwater drainage system diagnosis; (ii) a design proposal for micro-drainage and (iii) a SWOT analysis to propose improvement strategies in water management. The resulting ﬂows for return periods of 5 years, 10 years, and 25 years are 9.67 m 3 /s, 11.85 m 3 /s, and 15.85 m 3 /s, respectively. In the latter, as the most critical area (presence of ﬂooding), the implementation of a trapezoidal channel 80.20 m long, with a capacity of 1.00 m 3 /s, for a return period of 25 years was proposed. The stormwater masterplan will contribute to the execution of activities within the campus and prevent accidents and the proliferation of diseases, constituting a water-management model that can be replicated locally, regionally, and internationally.


Introduction
A hydrographic watershed is an area on the earth's surface that constitutes a natural drainage system for water captured by precipitation towards the same exit or gauging point [1]. These can be divided into sub-watersheds and micro-watersheds to make a more detailed analysis of the flow that enters and leaves [2]. One of the methods to assess the availability of water resources in a watershed is through the water balance, which analyzes the hydrological cycle by estimating the inflow of water through precipitation and its output process, which includes evapotranspiration, runoff, and infiltration [3].
In urban areas, the water cycle has another approach because it comprises of a series of stages. It begins with collecting and treating water that is supplied to the population and used in different activities that generate wastewater. Next, the generated wastewater is collected and transported through a systems of pipes to the treatment plants, to finally be returned to an effluent where it will have the effect of dilution by volume and does not deteriorate in quality [4].
The evapotranspiration, runoff and infiltration parameters will depend on the permeability of the soil, and in an urban watershed, this is a factor to consider. By 2030, Smart Cities 2023, 6, FOR PEER REVIEW 3 At the macro level, the existing drainage system works adequately; however, when zones carry out the analysis, it can be identified that, at the micro-drainage level, one of them works inefficiently because a civil structure (building) is in the natural drainage area. In this area, which is very busy, significant flooding has been recorded in the winter season, resulting in damage and impacts to the well-being of the university community. Following this problem, components should be considered that are crucial in the masterplan of a university campus that allow for flood and decrease the risk of vector proliferation, as well as the proposal of short, medium, and long-term interventions, and works that will improve the well-being of the campus community.
ESPOL constantly seeks to optimize the management of the drinking water, sanitary sewerage and stormwater sewerage systems to guarantee safe expansion in the short, medium and long term [53,54]. That is why, through analyzing the existing situation and applying technical criteria, this study proposed a masterplan as a comprehensive management model for flood control on campus, which will provide solutions that are viable on the economic level as well as sustainable. Furthermore, adequate flood control will mitigate the proliferation of vectors responsible for diseases and health effects.

Materials and Methods
ESPOL is considered the first green university in Ecuador, and according to the UI Green Metric World University Ranking, it is among the greenest universities in the world [55]. In addition, the campus has academic and administrative infrastructure areas and important areas declared as environmental protection areas.
Considering the morphology of the terrain and the meteorological conditions that condition the hydrographic system of the study area, it is important to develop stormwater-management projects that evaluate the behavior of the existing sewage infrastructure on campus and in populated peripheral zones. Furthermore, the hydrological analysis of watersheds and micro-watersheds is a fundamental tool in stormwater management in occupied areas with future expansion plans. In this case, to mitigate flooding problems within a university campus, work phases have been contemplated that include: (i) data collection and processing for the stormwater drainage system diagnosis; (ii) a design At the macro level, the existing drainage system works adequately; however, when zones carry out the analysis, it can be identified that, at the micro-drainage level, one of them works inefficiently because a civil structure (building) is in the natural drainage area. In this area, which is very busy, significant flooding has been recorded in the winter season, resulting in damage and impacts to the well-being of the university community. Following this problem, components should be considered that are crucial in the masterplan of a university campus that allow for flood and decrease the risk of vector proliferation, as well as the proposal of short, medium, and long-term interventions, and works that will improve the well-being of the campus community.
ESPOL constantly seeks to optimize the management of the drinking water, sanitary sewerage and stormwater sewerage systems to guarantee safe expansion in the short, medium and long term [53,54]. That is why, through analyzing the existing situation and applying technical criteria, this study proposed a masterplan as a comprehensive management model for flood control on campus, which will provide solutions that are viable on the economic level as well as sustainable. Furthermore, adequate flood control will mitigate the proliferation of vectors responsible for diseases and health effects.

Materials and Methods
ESPOL is considered the first green university in Ecuador, and according to the UI Green Metric World University Ranking, it is among the greenest universities in the world [55]. In addition, the campus has academic and administrative infrastructure areas and important areas declared as environmental protection areas.
Considering the morphology of the terrain and the meteorological conditions that condition the hydrographic system of the study area, it is important to develop stormwatermanagement projects that evaluate the behavior of the existing sewage infrastructure on campus and in populated peripheral zones. Furthermore, the hydrological analysis of watersheds and micro-watersheds is a fundamental tool in stormwater management in occupied areas with future expansion plans. In this case, to mitigate flooding problems within a university campus, work phases have been contemplated that include: (i) data collection and processing for the stormwater drainage system diagnosis; (ii) a design proposal for micro-drainage; and (iii) a SWOT analysis to propose improvement strategies in water management ( Figure 2). Smart Cities 2023, 6, FOR PEER REVIEW 4 proposal for micro-drainage; and (iii) a SWOT analysis to propose improvement strategies in water management ( Figure 2).

Stage I: Data Collection and Processing for the Stormwater Drainage System Diagnosis
The study began with collecting and processing data from the area that included: topography, population data, previous projects of the stormwater sewerage system, and meteorology, among others. Then, computer software such as Google Earth, CivilCAD, and ArcGIS made it possible to obtain the topography.
With the land's topography, we proceeded to delimit the sub-watershed and microwatersheds through the ArcGIS software using the Flow Direction and Flow Accumulation tools to determine the drainage areas of the micro-watersheds. The average between the results obtained from the Kirpich (Equation (1)) [56] and California (Equation (2)) [57] equation allowed us to determine the concentration time (t). The two methods are similar and useful in watersheds of medium size, have considerable slope, have soils dedicated to cultivation (mango planting in experimentation), and are widely used in the environment. For Equation (1), Lo is the length of the channel upstream to the outlet point, and S is the average slope of the basin; while for Equation (2), L is the length of the longest watercourse and H is the difference between the watershed and the outlet.
The analysis of different factors to determine the design flow of rainwater (Q) included: values of intensity (I), duration and frequency of average precipitation from the

Stage I: Data Collection and Processing for the Stormwater Drainage System Diagnosis
The study began with collecting and processing data from the area that included: topography, population data, previous projects of the stormwater sewerage system, and meteorology, among others. Then, computer software such as Google Earth, CivilCAD, and ArcGIS made it possible to obtain the topography.
With the land's topography, we proceeded to delimit the sub-watershed and microwatersheds through the ArcGIS software using the Flow Direction and Flow Accumulation tools to determine the drainage areas of the micro-watersheds. The average between the results obtained from the Kirpich (Equation (1)) [56] and California (Equation (2)) [57] equation allowed us to determine the concentration time (t). The two methods are similar and useful in watersheds of medium size, have considerable slope, have soils dedicated to cultivation (mango planting in experimentation), and are widely used in the environment. For Equation (1), Lo is the length of the channel upstream to the outlet point, and S is the average slope of the basin; while for Equation (2), L is the length of the longest watercourse and H is the difference between the watershed and the outlet.
The analysis of different factors to determine the design flow of rainwater (Q) included: values of intensity (I), duration and frequency of average precipitation from the nearest meteorological station (M0056) based on the data provided by the National Institute of Meteorology and Hydrology (INAMHI, acronym in Spanish) [58] (Table 1). This analysis aimed to determine the values of maximum precipitation intensities for a given return period T (2 years, 5 years, 10 years, 25 years, 50 years, 100 years). Subsequently, the determination of the runoff coefficient (C) depended on the surface characteristics in developed areas (e.g., asphalt, concrete, gardens, parks, among others) and undeveloped areas (e.g., crop areas, pastures, forests), making use of the Chow matrix [59] (Table 2). On the other hand, with the data on runoff coefficient (C), rainfall intensity (I), and estimated areas of the micro-watersheds (A), the calculation of the maximum runoff flows was carried out using the rational method (Equation (3)) [60], for different return times for micro-drainage (5 years, 10 years, and 15 years).
Finally, the diagnosis of the existing system included the identification of the sewers and channels that the university campus has for the transport of rainwater, with the respective information on diameters, sections, dimensions, and current conditions. For this, based on the measurements made, in the case of channels, the depth was estimated (Equation (4)), where H is the total height of the channel, which is the sum of the deep (y) and the free edge (FE), the FE being between 5% and 30% of the tightness [59,61]. Therefore, it was considered that pipes work at 75% of their capacity [62].
The study determined the capacity of the existing channel and pipe, using the depth of the water flow through the formula developed by Robert Manning [63], in which the estimated flow depends on parameters such as roughness coefficient (n), the hydraulic radius (R h ), longitudinal slope (S), and cross-sectional area (A) of the existing systems analyzed (Equation (5)). The value of n was taken from [63] and as the specialized literature on this subject indicates, this value depends on the type of material in which the channel or pipe is constructed (e.g., closed conduit, lined channel, natural flow, excavated) and the lining material.

Analysis Zones
Based on the flows that each of the micro-watersheds generates, the study evaluated the capacity of the existing channels, defining four main discharge sites (SD) (two that correspond to the macro drainage and two based on the problems identified in the site). For the proposed SDs, the capacity evaluation considered a return period of 50 years, which made it possible to define the venting areas that present flooding problems and the increase in infrastructure capacity and propose the respective solutions based on conditions in each site.

Constraint Analysis
The approach of alternatives that solve the problems identified in the area considered the already established constructions and the environmental conservation areas (protective forest and green areas). Similarly, it is important to consider technical criteria such as location, slope, and sector of influence. Therefore, the alternatives considered technical criteria (natural slope, location, area, previous studies, connection points) to guarantee the operation of the gravity system and avoid high operation and maintenance costs due to energy expenses when installing pumping stations. Additionally, the analysis considered sustainability criteria, including social (e.g., population growth, health emergency, road development), economic (e.g., construction costs, machinery costs, maintenance costs) and environmental (e.g., impact on forests, green areas) criteria.
Finally, these criteria take on values through an adaptation of the Likert scale [64], a semiquantitative methodology in which the assigned score depends on the opinion of the evaluators and the level of compliance with the parameter in the alternatives analyzed. The scores within this methodology include evaluations between 1 to 5 considering: (i) one is "totally unfavorable", (ii) two is "certainly unfavorable", (iii) three is "neutral or indifferent", (iv) four is "certainly favorable", and (v) five is "totally favorable" (Table 3). In addition, this study will analyze the alternative that obtains a higher score.

Stage III: SWOT Analysis
The study ended with an analysis of the main strengths, weaknesses, opportunities, and threats (SWOT) [66] of the campus storm sewer system, which allows the proposal of improvement strategies that guarantee the management of rainwater in the short, medium, and long term. This analysis contemplated a comprehensive approach that involved the participation of ESPOL campus authorities related to sustainable water management, civil engineers, and authors of the work.

Study Area Diagnosis
The campus has an irregular morphology that includes elevations between 25 and 450 m above sea level ( Figure 3) and maximum slopes of 45 • . This condition allows the formation of a series of natural drainages that preserve the protective forest and flow through a storm drainage system that avoids flooding problems on campus. The main buildings, where most of the university's activities occur, are mainly in the light-green zone.
According to the topographic data of the study area and the hydrological analysis performed in ArcGIS software, two sub-watersheds of 401.90 ha and 228.26 ha were delimited for sub-watershed one and two, respectively ( Figure 4). Sub-watershed 1 encompasses 90% of the campus infrastructure (target area for flood event analysis) and protective forest. On the other hand, sub-watershed two comprises an area designated for economic and sustainable development that includes experimental farms and part of the protective forest.
In the specific analysis, ten drainage micro-watersheds were determined ( Figure 5), with micro-watershed four occupying the largest area, with maximum slopes; on the other hand, micro-watershed two is the smallest area and has the lowest slopes ( Table 4). The drainage system obtained from the elevation and slope data reflects main and secondary channels that converge at two main water dump points (WDP) or outflow points to the north of the study area ( Figure 5). WDP1 collects the flow generated by sub-watershed one, while WDP2 collects the discharge from sub-watershed two.  According to the topographic data of the study area and the hydrological analysis performed in ArcGIS software, two sub-watersheds of 401.90 ha and 228.26 ha were delimited for sub-watershed one and two, respectively ( Figure 4). Sub-watershed 1 encompasses 90% of the campus infrastructure (target area for flood event analysis) and protective forest. On the other hand, sub-watershed two comprises an area designated for economic and sustainable development that includes experimental farms and part of the protective forest. In the specific analysis, ten drainage micro-watersheds were determined ( Figure 5), with micro-watershed four occupying the largest area, with maximum slopes; on the other hand, micro-watershed two is the smallest area and has the lowest slopes ( Table 4). The drainage system obtained from the elevation and slope data reflects main and secondary channels that converge at two main water dump points (WDP) or outflow points to the north of the study area ( Figure 5). WDP1 collects the flow generated by sub-watershed one, while WDP2 collects the discharge from sub-watershed two. In the specific analysis, ten drainage micro-watersheds were determined ( Figure 5), with micro-watershed four occupying the largest area, with maximum slopes; on the other hand, micro-watershed two is the smallest area and has the lowest slopes ( Table 4). The drainage system obtained from the elevation and slope data reflects main and secondary channels that converge at two main water dump points (WDP) or outflow points to the north of the study area ( Figure 5). WDP1 collects the flow generated by sub-watershed one, while WDP2 collects the discharge from sub-watershed two.   The water flow coming from WDP1 goes through an unlined channel that conveys the water to the outside of the campus (Figure 6a), to the sector called "Socio-Vivienda" (Figure 6b), passing through two pipes of Ø500 and Ø800 mm (Figure 6c). The flow of WDP2 discharges to the drainage system of a perimeter road (first-order highway). The water flow coming from WDP1 goes through an unlined channel that conveys the water to the outside of the campus (Figure 6a), to the sector called "Socio-Vivienda" (Figure 6b), passing through two pipes of Ø500 and Ø800 mm (Figure 6c). The flow of WDP2 discharges to the drainage system of a perimeter road (first-order highway).

Hydrological Study
The average values obtained from the Kirpich and California equations show a maximum concentration time (t) of 28.29 min corresponding to micro-watershed nine and a minimum of 7.40 min corresponding to micro-watershed three (Table 5). According to the times of concentration (Table 5), the rainfall intensity values reflect maximum values of 171.84 mm/hour in the return period T of 50 years for micro-watershed three. On the other hand, micro-watershed nine with an intensity of 69.15 mm/hour for a T of five years corresponds to the minimum intensity value in the study (Table 6). According to the classifications proposed by [59] and the slopes calculated for each micro-watershed, 70% of the area analyzed corresponds to pitches between 0 and 7% with maximum runoff coefficients of 0.92 at a T of 50 years. In contrast, 30% of the zone (microwatersheds 4, 7, and 10) with slopes greater than 7% reflect maximum runoff coefficients of 0.48 for a 50-year (T).
Although the ESPOL campus has many green surfaces that allow water filtration, micro-watersheds two and three have the highest runoff coefficient; this is because both areas contain most of the campus infrastructure, and due to the presence of concrete, the soil is less permeable, so rainwater runs off more easily (Table 7). Similarly, when reviewing other case studies, it can be seen how the runoff coefficient is higher in urbanized areas [67][68][69]. Table 7. Application of runoff coefficients in micro-watershed for the different return periods (T). For a return period of 50 years, the micro-watershed presents a maximum flow equal to 4.30 m 3 /s ( Table 8). The rational method allowed for estimating the average flow of the micro-watersheds with areas smaller than 139 Ha, which according to [70] the application of this method is ideal for watersheds smaller than 25 Km 2 (2500 Ha), demonstrated its efficiency in different studies [71][72][73].

Existing System Evaluation
The study considered four analysis points: (i) point A, where a large part of the flows generated by the different areas where many of the campus activities take place to converge; (ii) points B and C, which are the outlets for the entire ESPOL storm drainage system; and (iii) point D, characterized by being the busiest zone on campus, locating a cafeteria and other classroom buildings are located; the latter has local flooding problems. Figure 7 shows the location and slope value corresponding to the sections of each point. In point D, there are infrastructures where concrete covers a large part of the soil. Unlike the natural ground, concrete does not allow water loss by infiltration, favoring the flow transit [74], making the area vulnerable to flooding due to the abovementioned conditions [75,76].
Point A currently has a trapezoidal section channel, while in point B and C, there is a natural channel with a rectangular section. Finally, the drainage system in point D consists of a Ø500 mm diameter pipe (Figure 8). The capacity evaluation used Equation (5). In point D, there are infrastructures where concrete covers a large part of the soil. Unlike the natural ground, concrete does not allow water loss by infiltration, favoring the flow transit [74], making the area vulnerable to flooding due to the abovementioned conditions [75,76].
Point A currently has a trapezoidal section channel, while in point B and C, there is a natural channel with a rectangular section. Finally, the drainage system in point D consists of a Ø500 mm diameter pipe (Figure 8). The capacity evaluation used Equation (5). In point D, there are infrastructures where concrete covers a large part of the soil. Unlike the natural ground, concrete does not allow water loss by infiltration, favoring the flow transit [74], making the area vulnerable to flooding due to the abovementioned conditions [75,76].
Point A currently has a trapezoidal section channel, while in point B and C, there is a natural channel with a rectangular section. Finally, the drainage system in point D consists of a Ø500 mm diameter pipe (Figure 8). The capacity evaluation used Equation (5).  Initially, the study considered a FE of 30% of the depth for the capacity analysis of the channels of points A, B and C. However, for point D, as it is a pipeline, it was considered that it works at 70% of its capacity, as indicated in the standard. Therefore, for point A, the analyzes carried out considered a depth of 1.60 m and a roughness coefficient (n) equal to 0.017 to calculate the existing system capacity. The results indicate that for a return period of 50 years, the canal works at 10% of its capacity, with the canal's capacity equal to 55.25 m 3 /s, compared to a runoff flow of 5.41 m 3 /s (Table 9). In point B, for a discharge of 1.20 m and a n = 0.03, the calculated flow was 12.33 m 3 /s, so the channel would work at 110% for a return period of 50 years, representing problems in its hydraulic operation (Table 10). However, considering a free edge of 15% of the depth, the channel can drain 15.47 m 3 /s; therefore, for a return period of 50 years, the canal would be working at 87% of its capacity without overflow problems.
For the channel in point C, with n = 0.03, the depth obtained was 1.50 m. Therefore, for a return period of 50 years, the flow would work at 35% of its capacity, so it would not present any problems in its operation either (Table 11). In point D, with n = 0.014 for a minimum return period of five years, the corresponding flow would be 0.64 m 3 /s, which represents a problem because the pipe capacity is only 0.17 m 3 /s (Table 12). Finally, the map in Figure 9 shows the drainage system implemented on the campus, which consists of a canals system and pipes that transport rainwater to the natural drainage systems. The piping that presents capacity problems and would cause flooding during rainy seasons can be seen (Figure 10).

20
0.93 0.17 547% 25 1.00 0.17 588% Finally, the map in Figure 9 shows the drainage system implemented on the campus, which consists of a canals system and pipes that transport rainwater to the natural drainage systems. The piping that presents capacity problems and would cause flooding during rainy seasons can be seen ( Figure 10).

Evaluation of Alternatives Using a Likert Scale
Based on the problems encountered in Point D, the alternatives for the solutio as follows: • Alternative 1: Implementation of new channels and change of diameters in rece pipes; • Alternative 2: Implementation of green and blue solutions, creation of flood z green roofs, and use of permeable concrete.
The selected alternative that best fits the evaluated conditions considered the r obtained from the Likert scale, in which alternative one obtained a score of 36. For e ple, in the case of the slope, a value of one was considered for pitches against the dir

Evaluation of Alternatives Using a Likert Scale
Based on the problems encountered in Point D, the alternatives for the solution are as follows: • Alternative 1: Implementation of new channels and change of diameters in receiving pipes; • Alternative 2: Implementation of green and blue solutions, creation of flood zones, green roofs, and use of permeable concrete.
The selected alternative that best fits the evaluated conditions considered the results obtained from the Likert scale, in which alternative one obtained a score of 36. For example, in the case of the slope, a value of one was considered for pitches against the direction of flow, two for slopes equal to zero, three for slopes between 0% and 2%, four for slopes between 2% and 7%, and five for slopes between 7% and 15%. Similarly, the assessment of the other conditions was carried out (Table 13). The Likert scale assessment method allows the measurement of the conditions presented by different scenarios in a qualitative or semiquantitative manner. Therefore, this study assessed two alternatives regarding technical, social, economic and environmental factors, as has been done in other studies [12,77,78].

Desing of Selected Proposal
The hydraulic performance of the selected alternatives contemplated a maximum return period of 25 years. The flow velocity for the proposed trapezoidal channel fluctuates between 1.50 m/s to 1.65 m/s, within the permissible range (Table 14). The results indicate that the existing pipe needs to be replaced by another one with a diameter equal to Ø1.10 m, resulting in a flow velocity of 1.65 m/s, complying with the minimum diameter and velocity requirements (Table 15). For the design of both solutions, the slope is equal to 0.003 m/m, which allows for obtaining a flow velocity within the range established by local regulations.  The proposed channel and the pipe contemplate a length of 80.20 m, and because point D is a busy sector, the channel must be closed in certain sections. Therefore, the design of the proposed pipe considered that it should work at 80% of its capacity. The lining material of the channel, as well as that of the piping, is concrete ( Figure 11). The flooding in point D is a consequence of inadequate planning, as it needs t sider the flow generated for a return period of 25 years following local regulatio addition, the diameter of the existing pipe, despite being greater than the minimum ommended, needs more capacity to drain the water generated in this micro-waters These floods generated cause material and health problems; therefore, impleme an adequate drainage system will prevent the stagnation of water, which is the mean allow organisms carrying diseases such as dengue or malaria, characteristic of tr climates such as Ecuador, to proliferate [79].
Although the material damage present in the area does not reflect a significant ity, inefficient planning can lead to more serious consequences; such as the case of happened on 31 January 2022 in the city of Quito, Ecuador, in the sector known Gasca, where a landslide, which consists of a flow of abundant water that drags w loose material from a hillside or stream [80], occurred which left a total of 170 peo fected, 28 dead, 41 houses affected, and seven houses destroyed. In addition to mo logical conditions such as the presence of hillsides and ravines [81], inadequate ma ment of the city's natural drainage, and poor territorial planning coupled with deton events such as heavy rains or earthquakes, can increase vulnerability to flooding [8 These events, under similar conditions, have also occurred in other areas of the (e.g., [84][85][86]) affecting infrastructure and the safety of inhabitants.

SWOT Analysis
The strategies proposed in the SWOT analysis focus on optimizing the campu water drainage system to avoid health problems and flooding. The analysis of ex and internal aspects established strategies that promote the integral participation thorities, teachers, students and ESPOL staff, as well as the application of sustainable niques that allow the reuse and use of rainwater for different purposes and activit The flooding in point D is a consequence of inadequate planning, as it needs to consider the flow generated for a return period of 25 years following local regulations. In addition, the diameter of the existing pipe, despite being greater than the minimum recommended, needs more capacity to drain the water generated in this micro-watershed.
These floods generated cause material and health problems; therefore, implementing an adequate drainage system will prevent the stagnation of water, which is the means that allow organisms carrying diseases such as dengue or malaria, characteristic of tropical climates such as Ecuador, to proliferate [79].
Although the material damage present in the area does not reflect a significant severity, inefficient planning can lead to more serious consequences; such as the case of what happened on 31 January 2022 in the city of Quito, Ecuador, in the sector known as La Gasca, where a landslide, which consists of a flow of abundant water that drags with it loose material from a hillside or stream [80], occurred which left a total of 170 people affected, 28 dead, 41 houses affected, and seven houses destroyed. In addition to morphological conditions such as the presence of hillsides and ravines [81], inadequate management of the city's natural drainage, and poor territorial planning coupled with detonating events such as heavy rains or earthquakes, can increase vulnerability to flooding [82,83]. These events, under similar conditions, have also occurred in other areas of the world (e.g., [84][85][86]) affecting infrastructure and the safety of inhabitants.

SWOT Analysis
The strategies proposed in the SWOT analysis focus on optimizing the campus rainwater drainage system to avoid health problems and flooding. The analysis of external and internal aspects established strategies that promote the integral participation of authorities, teachers, students and ESPOL staff, as well as the application of sustainable techniques that allow the reuse and use of rainwater for different purposes and activities on campus (Table 16). Table 16. Strengths, weaknesses, opportunities, and threats (SWOT) matrix analysis of current and proposed sewer system. The SWOT combining internal environment (strengths and weaknesses) identified by numbers 1 to 4 and the external environment (opportunities and threats) identified by letters (a) to (d).

Internal Environment
Strengths Weaknesses In general, from the analysis, the importance of raising awareness among the population regarding water care through the application of nature-based solutions (NBS) is rescued. Among these, for flood control, there are green-blue infrastructures such as green roofs, retention, and detention ponds (albarradas in spanish), renaturalized rivers without sewers, ditches and 'bioswales', or rain gardens, generating a positive impact on social and environmental well-being [87][88][89]. However, the NBS should only sometimes be im-plemented as a solution since this will depend on the conditions of the problem and the environment where it develops, as has been done in other studies [90,91].
From the SWOT analysis, the recommendations mainly focused on the rescue of ancestral knowledge arise through the construction of albarradas for the natural storage of water, an NBS alternative that has little impact on the environment and whose effect on the hydrological cycle of water is minimal [92][93][94]. However, it is important to highlight that poor management would promote the proliferation of vector organisms such as rats, ticks, or mosquitoes [95].
Usually, the investment allocated for implementing these infrastructures is minimal due to a lack of knowledge or economic limitations, which translate into a cognitive bias [96,97]. Due to this, in the study area and general in the country, it is necessary to implement water policies that involve and promote NBS as efficient alternatives to technological solutions.
ESPOL has large extensions of green areas within the campus, in which implementing NBS would favor the ecosystem. However, point D represents a specific problem of strangulation of the drainage system due to the lack of capacity of the existing system. Therefore, as an immediate solution, it was proposed to increase the system's capacity using a trapezoidal channel or the replacement of the pipe with one with a larger diameter.
The proposed solution for the area with the flooding problems complements the study carried out [98], in which the implementation of NBS on the university campus was analyzed, such as rain gardens, infiltration fields, cisterns and permeable stone paving blocks. In his study, he considered the implementation of permeable stone paving blocks in an area containing point D. It was concluded that this solution has an efficiency of only 6.59% because it is a low point where other sub-watersheds are located. Therefore, implementing a technical solution through a trapezoidal channel or pipe replacement responds more effectively to adequate water transport and flood mitigation.
This study complements the masterplans proposed for the sanitary sewerage and drinking water systems [53,54], strengthening the management of water and sanitation on the ESPOL campus through technical, social, environmental, and economic criteria through specific technical solutions in areas with flooding problems. In addition, the masterplan contemplates NBS components that could be applied in the medium and long term in environmental protection, avoiding the disturbance of ecosystems by engineering works. Furthermore, implementing the designed proposals promotes and creates awareness in the ESPOL community about the circular economy of water and offers the appropriate environment for the different geotourism and geoeducation activities, considering the geological and biodiverse wealth of the campus [52].
The integration of technical solutions and NBS on the university campus represents a responsible and preventive water-management model before future scenarios, which can be replicated at the regional level as an alternative to mitigate climate change's effects [99,100] and contribute to fulfilling the fulfillment of Sustainable Development Goals (SDGs) of UNESCO [101,102].

Conclusions
The masterplan allowed for the global drainage evaluation, determining that the system does not present problems at the macro level. Three essential aspects stand out from the results obtained:

•
The integration of technical-academic knowledge in the development of a stormwater masterplan for a university campus demonstrated the importance of water management in areas where, despite not being considered, poor planning generates damage to infrastructures and put the health of inhabitants at risk; • The development of SWOT analysis in decision-making for managing water resources allows for the proposal of holistic strategies from the social, academic, and governmental points of view, which guarantee the functionality of sewerage systems and water reuse in the short, medium, and long term; • Ancestral (traditional) knowledge is important through NBS for collecting and managing water, as 3E (Ecological, Economic, Effective) alternatives, and are replicable locally and regionally.