SUSTAINABLE RAINWATER MANAGEMENT WITH THE USE OF COMPENSATORY URBAN DRAINAGE TECHNIQUES: CASE STUDY ON THE MARACANÃ CAMPUS OF THE UNIVERSITY OF THE STATE OF RIO DE JANEIRO (UERJ)

Objective: The objective of this study is to evaluate the hydrological impact of using different compensatory techniques on the conventional urban drainage system in an intramural contribution basin to the Maracanã Campus of the State University of Rio de Janeiro (UERJ), located in the Maracanã neighborhood, in the city from Rio de Janeiro-RJ. Theoretical Framework: A bibliographical review was prepared with an approach to the urbanization process associated with urban drainage infrastructures, as well as the use of compensatory techniques to control urban flooding. Method: Rainfall and hydrological data, demand and consumption of non-potable water in the building, sizing of the microdrainage network and compensatory techniques and calculation of the runoff buffered by the techniques were obtained. Results and Discussion: The results obtained revealed that the hydrological impact of using compensatory techniques designed on the drainage network designed in the Maracanã Campus basin, which discharges a flow of 2,041.66 Lts/s, would have a reduction in the flow of around 19%, using only around 14% of the Campus area is a contribution area for techniques. Research Implications: The research brings a scientific contribution based on the analysis of the implementation of compensatory techniques on the microdrainage network as an alternative to be evaluated by municipal managers as a solution to be integrated into the infrastructure development of cities, in order to make them more resilient in terms of to intense rainfall events. Originality/Value: The study showed, based on the results obtained, the efficiency in the use of compensatory urban drainage techniques, with discussion in the scientific community to develop further studies in the context of water resources management.


INTRODUCTION
Phenomena related to the risks of extreme hydrological events have been observed in Brazil and around the world, such as water scarcity and urban flooding.
According to the National Water Agency's Economic Report (Ana, 2023), from 2020 to 2022, approximately 25 million people were affected by droughts and droughts in Brazil, which corresponds to around 6 times more than by floods.4,195 drought events associated with human damage were quantified, around 3.5 times more than floods (1,188).In 2022, more than 7 million people were affected by droughts and droughts in Brazil, with 1,212 events recorded this year.In terms of human damage, 2021 was more critical than 2022, with around 700,000 more people affected by drought and drought events.
There are still few public policies to mitigate problems caused by risks from hydrological extremes.In Brazil, there is disregard for the protection of river basins, and irregular constructions in marginal protection strips, dumping of untreated sewage and silting of rivers.
A large part of the population of the city of Rio de Janeiro suffers from problems related to flooding, caused by intense rains.This disorder has serious repercussions, such as the growing number of irregular occupations and problems related to inadequate waste disposal, with numerous urban impacts, in addition to irreparable loss of human life.Therefore, the implementation of effective solutions to mitigate the causes and consequences caused by floods becomes an increasingly priority (Ottoni, 2018).
In terms of drainage and sewage systems, a series of structures and operating conditions persist in the city of Rio de Janeiro that indicate the high degree of interconnection between sanitary sewage and rainwater drainage systems, which contributes to environmental degradation and the vulnerability of these sanitation systems (Dias and rosso, 2009).
In order to mitigate the impacts of urbanization, urban drainage techniques were developed that seek to mitigate flow peaks, generated by surface runoff and aggravated by 4 sustainable development (Miguez et al., 2016).
According to Tassi et al. (2016) and Melo et al (2016), the hygienist concept of capturing rainwater through storm drains and conveying it through galleries to macrodrainage channels must be accompanied by compensatory techniques, which are based on the detention and retention of precipitated water that aim to reduce surface runoff and its transfer downstream, and thus maintain the natural balance of the water balance.
This hygienist strategy proved to be effective, but over time, given the dynamics of human and urban development that would be observed and the climate changes that followed, it led to undesirable consequences in the urban environment, such as environmental degradation in several areas of cities and receiving water bodies.Currently, the classic drainage project has proven to be environmentally unsustainable, especially in developing countries with their wellknown social and economic problems, which contribute to the worsening of problems in the development of water resources that have come to be observed (Nunes et al. 2017).
In this context, the present work has the following hypothesis: the sustainable management of rainwater with the use of compensatory urban drainage techniques is capable of achieving a significant reduction by dampening the peak flow rate of the flow of a hygienic system, with the storage of volumes drained, it is possible to partially or completely meet the demand used for non-potable purposes, such as flushing toilets, watering and cleaning, in general, as in the case of using rainwater, at the Maracanã Campus, of the State University of Rio de Janeiro , in the city of Rio de Janeiro-RJ.

THEORETICAL REFERENCE
The phenomenon of urbanization is recognized as a complex process, intrinsically linked to the increase in population density that migrates from rural to urban areas.According to scholars, cities are products of this process, and urbanization plays a fundamental role in transforming the economic, social and cultural aspects of a society (Hussain;Imitiyaz, 2018).
According to Nunes and Rosa (2020), the increasing process of soil sealing results in direct impacts on hydrological dynamics.Specifically, increases in effective precipitation stand out, in speed with the consequent reduction in concentration time, as well as an increase in the volume of surface runoff, the resulting intensity of which can be seen in environments with greater flow convergence, such as headwaters and water channels.drainage.
According to Machado et al. (2022) the lack of control over land use and occupation is an important factor that highlights the occurrence of recurrent floods and landslides, with fatal victims and homeless people.
One of the serious problems in this urban development process is the expansion, generally irregular, into areas of water sources, compromising the water sustainability of cities (Tucci, 2002).This urban growth is marked by the disorderly expansion of peripheral areas, with little respect for urban regulations and subdivision rules.This tendency makes it difficult to organize non-structural actions in urban environmental control.
Drainage planning, as a management and decision-making tool for administrators, aims to reduce the financial costs necessary to mitigate the damage and social impacts resulting from the lack of this practice.Currently, flood control measures can be adopted at the local level and conventional measures in the river basin.However, to plan and execute these measures realistically, a thorough and careful analysis of the river basin is crucial (Costa Junior et al., 2006).
According to Nunes et al. (2017) an innovative approach to change projects aims to ensure a positive relationship between man and the environment, integrating urban development with the management of land use and occupation.The new standards and plans aim to compensate for changes in the hydrological cycle caused by urbanization by building green infrastructure throughout the basin and helping to control the quality and quantity of surface runoff.
Compensatory techniques are a segment of sustainable development, which act on drainage systems in order to regularize or increase hydraulic efficiency, thus playing a role in controlling floods and urban floods.
Compensatory techniques for controlling urban floods, such as: the use of porous pavements, water storage on roofs, the construction of small residential tanks and dense wells, which produce a distributed reduction in the effect of urbanization, are devices that in the literature have already demonstrate efficiency in their applications (Tucci, 1995).

STUDY AREA
The selected drainage area is a subdivision of the main campus of the State University of Rio de Janeiro, located in the Maracanã neighborhood, in the city of Rio de Janeiro-RJ, with consolidated urban infrastructure and registration of the microdrainage network, available in the UERJ City Hall collection (Figure 1).
The criteria used to select the study area were based on structural factors and space availability for the allocation of compensatory techniques for sizing, easy access to the necessary files, as well as the absence of a contribution from an external basin to the existing network, and the possibility of future complementary interventions, with the use of compensatory measures in rainwater management.Based on the processing of orthoimage data, the characteristics of each class of land use and occupation in UERJ were obtained, as described in Table 1.
Where:  2. The Rio Águas technical instruction manual (2019) suggests that the raining time is equal to the concentration time.In microdrainage projects, when the upstream area is urbanized or is in the process of urbanization, with a watershed at a distance of approximately 60 m, the initial concentration time will be obtained in Table 3: For other cases, the concentration time can be calculated using George Ribeiro's formula or Kirpich's formula, relating to the route over the thalweg, and Kerby's formula, relating to the route over natural terrain; for channels, the adoption of the Kinematic Method is recommended.
The concentration time adopted must not be less than 5 minutes.In this study, a concentration time of 10 minutes was considered, as assessed in Table 3, for areas with dense construction and gutter slope < 3%.The hydrological calculation methodology for determining project flows was defined based on the river basin areas.In the study in question, due to the basin area being less than 100 hectares, the Modified Rational Method was defined to determine the flow.
The flow calculation using the Rational Method modified with the inclusion of the Fantolli criterion is determined by Equations 2 and 3: Where: Where: In the Rational Method, the value of the basin's surface runoff coefficient will be determined from the weighted average of the partial area coefficients.
To define the value of the surface runoff coefficient for each type of land occupation at UERJ, the values in Table 4 by Rio-Águas (2019) were used, in accordance with the survey and characterization of land use and occupation.

SIZING RAINWATER TANKS
In 2019, NBR 15,527 was updated, abolishing the previously presented sizing methods, with the aim of giving greater autonomy to the designer, allowing adaptation to the specific conditions of each location, as well as cost optimization and consideration of the owner's preferences.
Regarding the volume of rainwater storage reservoirs, ABNT NBR 15.527/2019 provides: 4.4.2The volume of the reservoir(s) must be sized taking into account the catchment area, rainfall regime and non-potable demand to be met.4.4.10The volume of reservoirs must be sized based on technical, economic and environmental criteria, taking into account good engineering practices.(ABNT, 2019).
In the present work, the consecutive dry days (DSC) method is used to size the rainwater reservoir, with the objective of meeting the demands for the use of non-potable water.This 12 approach is justified, especially during periods of prolonged drought and in situations of restrictions on the use of drinking water imposed by local concessionaires.
To calculate the volume of rainwater usable by the system, Equation 4established by NBR 15527/2019 is used.
Where: From the analysis of the historical series of daily precipitation from the rainfall station closest to the study region, the largest period of days without rain in each year is obtained, and then the volume necessary to meet the demand for the period is calculated. of drought.
The method considers daily precipitation below 1 mm as dry days and uses Equation 5as a statistical model of the Gumbel probability density function to analyze the frequency of the consecutive dry days (DSC) event: Where: x = consecutive dry days (DSC); ̅ = average of consecutive dry days; Σ = Sample standard deviation; TR = payback period in years.
The reservoir storage volume is obtained based on the calculation of the DSC (consecutive dry days) and the daily consumption of non-potable water (Cd in liters/day), in response to prolonged periods of drought, according to Equation 6.According to Tomaz (2003), the use of rainwater is always used as non-potable water, for watering gardens, cleaning patios, flushing toilets, washing vehicles, industrial uses, in fire reservoirs and other uses that are not require potable water.There is a way to estimate residential drinking water consumption according to engineering parameters.The main difficulty in applying the parameters is the volume of necessary information that is not always available.
Tables 5 and 6 show the engineering parameters used in the United States for residential water consumption.According to Vasconcellos (2022), assortivity is a variable that describes an aspect of water-soil interaction, therefore, it depends on the attributes of the two elements and must be associated with a safety factor, as due to the accumulation of fines at the interface between the soil and the Over time, its infiltration capacity decreases.
For this work we will use the assortative value found by Vasconcellos (2022) which is 0.00069 m³/s.m².
The following infiltration rate reduction rates were suggested by Ciria (1996), taking into account the contribution area and the degree of impact of the structure, these values were presented in Table 7.

Table 7
Safety factors for reducing assortativity To design the permeable pavement technique, the envelope curve method was also used, adapted to the conditions of the surface type.
As with the infiltration trench, it is necessary to provide spillways for the existing drainage, due to floods with return periods that exceed the project capacity.
In this specific case, it is necessary to transform the parameters from the conventional IDF to the so-called Talbot IDF.It is worth noting that after the conversion, the parameter must be corrected, so that the result of an intense rain calculated by Talbot's IDF is the same as that calculated by Equation 1 of the conventional IDF (Silveira and Goldenfum, 2007).
Where: The soil infiltration rate is the constant output flow of the device and is obtained from Equation 16. 18 Where: = soil infiltration rate, in mm/h;  = reduction coefficient due to clogging and; = hydraulic conductivity of the saturated soil, in mm/h.
The parameter β relates the permeable pavement area and its contributing area, it is the product of the runoff coefficient and the ratio between the contributing area and the device area, in the case represented by Equation 17. Where: Apav = area of permeable pavement, in m²; Ac = contribution area that drains to the pavement, and; Ce = weighted runoff coefficient.
The calculation of the thickness of the pavement reservoir layer is obtained by Equation 18. Where: η is the porosity of the filling material of the porous layer.Based on the historical series available from 1997 to 2022, an average rainfall of 125.25 mm can be found as shown in Figure 3.

Figure 3
Average monthly precipitation at Tijuca station Analyzing the information obtained through Graph 1, we can observe that the wet period covers the months of November to April, highlighting the month of December with an average rainfall of 185.62 mm and the dry period is contained between the months of May to October, with the month of August characterized as the month with the least rain in the region, with an average of 64.23 mm of average precipitation.Based on information related to the UERJ infrastructure, obtained through an "on-site" survey, Table 8 was prepared, with the number of toilets, urinals and garden areas for the use of water for non-potable purposes.In addition to this verification, it was possible through the use and occupation of UERJ, a complementary survey of garden and grass areas for irrigation using non-potable water.Based on the information contained in the project, such as manhole elevation information (PVs), storm drain arrangements (BLs) and the network itself.
In the Draenar software environment, you can enter project data and information obtained from the rain gauge at Sabóia Lima station, regarding precipitation, and calculate project rainfall with the IDF equation (Equation 1).For information on the drainage network infrastructure, the definitions of the Drenar software were maintained, as shown in Figure 4, such as: floodable width of the streets (180 cm), height of the guide (20 cm), transverse slope of the gutters (5%), gutter manning coefficient (0.015), etc.  and 4.

23
After launching the routines and calculating the devices according to the flow in Figure 5, we have the result of the network sizing in Table 10.

Figure 5
Drain Sizing Flow Analyzing the results obtained by sizing the microdrainage network, it can be seen that the 93,172.71m² of the Maracanã Campus' contribution basin surveyed were divided into 49 sub-basins in which they flow through all 75 designed gutters, where at a flow rate of 2,661 .65 Lts/s that launch into their respective 0.70m long and 0.90m deep storm drains.In some cases, due to the load capacity of the BL, it is necessary to provide 2 or 3 devices in series.The interconnections of the storm drains were designed using 400mm connection pipes that direct rainwater to discharge a flow rate of 2,041.66Lts/s through the 13 designed points.

SIZING OF COMPENSATORY TECHNIQUES
The compensatory techniques were designed according to the scenario proposed in Figure 6.

Figure 6
Compensatory Techniques Rental Scenario

Reservoir Sizing
The results presented according to the application of the methodology and calculations presented in Chapter 3 of this work, we have the results of sizing the rainwater collection reservoirs described in Tables 11 and 12.

Trench Sizing
For this technique, three trenches identified as TR1, TR2, TR3 with rectangular section were provisioned, with sizing parameters defined in Table 13.
Due to the absence of physical parameters of the UERJ soil, values obtained by Vasconcellos (2022) were adopted.The sizing of the trenches is summarized in Table 14.

Table 14
Sizing infiltration trenches

Permeable Pavement Sizing
To size the maximum storage volume in the PP reservoir, the so-called Envelope Curve Method is considered, based on the derivation of the concentrated continuity equation, where the maximum storage Vmax is given by the maximum difference between the curves of accumulated inlet and output from the control structure.
To design the permeable pavement, some pre-defined parameters were taken into account, as shown in Table 15.For this work, the criterion for converting parameters from the conventional IDF to the so-called Talbot IDF was used, where: With data from the IDF of Sabóia Lima and transformation with Talbot, we have the correlation described in With the data in the Table , the new values of a, b, and c were calculated.
For this technique, three trenches identified as PP1, PP2 and PP3 were provisioned, with sizing parameters defined in Table 17.The design of permeable pavements is summarized in Table 18.

Table 18
Sizing infiltration trenches

Consolidation of the Results of Compensatory Techniques
For the proposed scenario of implementing compensatory techniques, they state that the UERJ, in an event with the projected rainfall intensity, would buffer a flow of 387.32 Lts/s, as indicated in Table x.The permeable pavement compensatory technique presented the highest weighted average of damped runoff depending on the contribution area with 59.91 Lts/s, followed by the reservoirs which obtained 34.43 Lts/s and the trenches with a calculated average of 22.85 Lts/s.
Analyzing the specific flow data, it can be stated that the compensatory technique with the least efficiency in absorbing the runoff was the infiltration trench, which is largely due to the characteristics of land use and occupation, as the devices designed had large areas of contribution from permeable soils, which reduces surface runoff as rainwater tends to infiltrate.
On the other hand, the compensatory technique with the highest runoff amortization efficiency were the five rainwater harvesting reservoirs precisely because we considered a runoff coefficient of 0.9, which means that only 10% of the precipitated water is lost, another important factor.What should be highlighted is the possibility of non-potable use of water, which contributes to savings in drinking water consumption.

CONCLUSION
From the results presented in this work, it is concluded that in a general context of sizing the UERJ microdrainage network prepared using the Drenar software, hydraulic insufficiency was found in the project for the sizing of gutters, storm drains, connection pipes, wells visit and the sections of the rainwater network, it was verified that the available project has differences with the existing network prospected "in situ", however this work dimensioned these devices to meet the project rainfall intensity with pre-established parameters and boundary conditions.
During the survey of the existing rainwater network, it was not possible to determine whether in fact what exists in the project made available by the City Hall is real, as it was possible to verify the flow of water on days without rain at the bottom of some PVs identified as belonging to the network, which we can conclude that there is cross flow with the sewage network or air conditioning system drainage.It was also possible to verify the existence of operating and silted storm drains that were not identified in the project.
The implementation of compensatory techniques aims to evaluate the damping of peak flows and generated volumes.
The five rainwater harvesting reservoirs resulted in a dampening of the runoff of 149.96 Lts/s and proved to be the most efficient compensatory technique in terms of specific flow, together they also have a storage capacity of around 226 m³, which is sufficient to meet nonpotable demand for 26 consecutive days without rain.
The three infiltration trench devices dampened a flow of 66.06 Lts/s, having a significant impact on dampening the surface runoff that should direct the designed gutters.The permeable pavement technique used a catchment area of 5,446 m² and a flow damping of 171.3 l/s, also being very efficient in dampening the flows that flow into gutters with the same contribution area.
In general, it is concluded that the hydrological impact of using compensatory techniques designed in this study on the drainage network designed in the Campus Maracanã basin, which discharges a flow of 2,041.66Lts/s, would have a reduction in the flow of approximately 19 %, using only around 14% of the Campus area as a contribution area for techniques.
The results obtained in this research demonstrate that the implementation of compensatory urban drainage techniques, which have the characteristics of increasing the storage capacity and infiltration of rainwater, is an alternative to be evaluated by municipal 32 managers as a solution to be integrated into the development of infrastructure of cities, in order to make them more resilient when it comes to intense rain events.
waterproofing.Such techniques bring together urban planning concepts and drainage systems, shared responsibility between the public sector and owners, in addition to being guided by The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.
Figure 1Study Area

Figure 2
Figure 2 Classification of land use and occupation of the UERJ Maracanã Campus area, Rio de Janeiro-RJ i = rain intensity (mm.h-1);T = payback period (anos); t = duration of rain (min); e a, b, c e d are the parameters of the equation, as shown in Table Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1 Monthly available volume of rainwater (l); P = Average monthly precipitation (mm); A = Contribution area (m²); C = Cover surface runoff coefficient (runoff) and; η = Efficiency of the capture system (in the absence of data, a capture factor of 0.85 is recommended).
volume in liters; Cd = daily consumption of non-potable water, in liters per day; It is DSC = consecutive dry days, in days.
soil sortivity with application of the safety factor, in m³/s.m²;S = assortivity of the experimental soil, in m³/s.m²,and; FS = Safety factor.Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.17 3.8 PERMEABLE FLOOR SIZING volume, in m³; a, b e c = parameters of the Talbot IDF equation; β = product of the runoff coefficient by the ratio between the contributing area and the device area; T = recurrence time, in years, and;   = soil infiltration rate, in mm/h;

Sustainable
Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1used in the work are made up of records obtained from the Tijuca rainfall station (Alerta Rio, 2023).
THE MICRODRAINAGE NETWORK -DRAINTo size the existing network, the available routines of the Draenar software were used, within the CAD environment.Based on the project provided by the UERJ city hall, we can verify the infrastructure of the existing drainage network.

Table 3
Concentration time for urbanized areas Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.

Table 5
Engineering parameters for estimating residential water demand

Table 6
Engineering parameters estimates of residential demand for drinking water for external use Iac = accumulated infiltration, in m³/m²; S' = soil assortativeness with application of the safety factor, in m³/s.m²,and; t = rain time, in seconds.
Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.
Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.

Table 8
Survey of devices for sizing water demand The result of the demand estimate, based on the values presented in Tablex, for UERJ, is presented in Table9.For toilet flushing in employee bathrooms, 22 days of use were used per month, and a frequency of 1 use per day per person and for irrigation, 4 waterings per month were considered.

Table 9
Estimated monthly consumption of non-potable water at UERJ Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.
Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.

Table 10
Microdrainage network sizing resultSustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.

Table 11
Maximum usable volume of reservoirs

Table 12
Reservoir sizing

Table 13
Parameters adopted for sizing trenches 1

Table 15
Parameters for pre-sizing permeable pavement

Table 17
Parameters adopted for designing permeable pavement

Table 19
Summary of the flow damped by each compensatory technique Sustainable Rainwater Management With the Use of Compensatory Urban Drainage Techniques: Case Study on The Maracanã Campus of the University of the State of Rio De Janeiro (UERJ) ___________________________________________________________________________ Rev. Gest.Soc.Ambient.| Miami | v.18.n.3 | p.1-33 | e06774 | 2024.