Universidade Federal de Santa Maria

Ci. e Nat., Santa Maria, v.42, e97, 2020

DOI:10.5902/2179460Xe40562

ISSN 2179-460X

Received: 12/11/19   Accepted: 30/04/20  Published: 23/12/20

 

 

Environment

 

Environmental diagnosis of the lower course of the Gigante river basin (Amazonas – Brazil)

 

Diagnóstico ambiental do baixo curso do Igarapé do Gigante (Amazonas – Brasil)

 

Jamerson Souza da Costa^I
Liange de Sousa Rodrigues^II
Mayra Rejane Moreira Mendonça^III

Maria da Glória Gonçalves de Melo^IV

Maria Astrid Rocha Liberato^V

 

^I Universidade do Estado do Amazonas, Manaus, AM. E-mail: jamersonjsc@yahoo.com.br.

^II Universidade do Estado do Amazonas, Manaus, AM. E-mail: li_rodriguess212@hotmail.com.

^III Universidade do Estado do Amazonas, Manaus, AM. E-mail: mayrarejane@hotmail.com.

^IV Universidade do Estado do Amazonas, Manaus, AM. E-mail: mgmelo@uea.edu.br.

^V Universidade do Estado do Amazonas, Manaus, AM. E-mail: mliberato@uea.edu.br.

 

ABSTRACT

The watershed is a complex system that goes beyond the drainage network, involving all the ecosystem aspects within its limits. Despite the set of ecohydrological functions that its components play in the protection of water resources, especially the vegetal cover, hydrological systems are the ecosystems that suffer the most changes due to anthropic activities, notably when inserted in the urban environment. Thus, this work aimed to perform the environmental diagnosis of the lower course of the Gigante river basin, in Manaus-AM. We carried field visits, collecting and registering information about the study area, applying check-list, interaction network and interaction matrix methods. Through the environmental diagnosis, we evaluated that the low course of the Gigante River presents areas where native vegetation has been suppressed, including permanent preservation areas, triggering several impacts of other orders, such as exposure and waterproofing of the soil, silting, introduction of exotic species, excess aquatic vegetation, effluent and solid waste. The proposed mitigation measures were to eliminate the emission of effluents and deposition of solid wastes, to remove the invasive species and to lead the natural regeneration and/or the enrichment of the area.

Keywords: Environmental impact; Deforestation; Restoration

 

RESUMO

A bacia hidrográfica constitui um sistema complexo, que vai além da rede de drenagem, envolvendo todos os aspectos ecossistêmicos compreendidos nos seus limites. Apesar do conjunto de funções eco-hidrológicas que seus componentes desempenham na proteção dos recursos hídricos, especialmente a cobertura vegetal, os sistemas hidrológicos são os ecossistemas que mais sofrem alterações em razão de atividades antrópicas, principalmente quando inseridos no meio urbano. Dessa forma, este trabalho objetivou realizar o diagnóstico ambiental do baixo curso do Igarapé do Gigante, em Manaus-AM. Para tanto, realizou-se visitas a campo, com coleta e registro de informações sobre a área de estudo, aplicando-se os métodos de check-list, rede de interação e matriz de interação. Por meio do diagnóstico ambiental, avaliou-se que o baixo curso do Igarapé do Gigante apresenta áreas onde houve a supressão da vegetação nativa, incluindo áreas de preservação permanente, desencadeando diversos impactos de outras ordens, como a exposição e impermeabilização do solo, assoreamento, introdução de espécies exóticas, excesso de vegetação aquática, aporte de efluentes e resíduos sólidos. As medidas mitigadoras propostas foram eliminar a emissão de efluentes e a deposição de resíduos sólidos, retirar as espécies invasoras e conduzir a regeneração natural e/ou o enriquecimento da área.

Palavras-chave: Impacto ambiental; Desflorestamento; Recuperação

 

1 Introduction

The watershed is a complex system that goes beyond the drainage network, involving all the ecosystem aspects within its limits. Despite the set of ecohydrological functions that its components play in the protection of water resources, especially the vegetal cover, hydrological systems are the ecosystems that suffer the most changes due to anthropic activities. Awareness of the need to protect these environments, as well as the foundations of environmental impact assessment processes, gained ground since the late 1960s, when discussions began that resulted in the concept of sustainable development and the prioritization of actions of rational production and consumption that respect the resilience of ecosystems. This assessment should follow flexible methods that suit the environmental aspects considered (CREMONEZ et al., 2014).

In the same period, the watershed was consolidated as a basic unit of study and planning, being a reference in the evaluation of the environmental impacts suffered in its drainage area, considering the systemic response that involves the landscape and its biophysical elements and anthropic activities developed there (SANTOS et al., 2015). This holistic vision must also underpin the management of natural resources, as required by forest and water legislation, and in compliance with the goals agreed in the United Nations Agenda 2030, to achieve the Sustainable Development Goals – SDGs (BRAZIL, 1997; 2012; UN, 2015).

According to Rieger et al. (2014) and Rodrigues et al. (2015), the interface region between aquatic and terrestrial environments formed by riparian vegetation acts as a natural barrier to protect water bodies against erosion, sedimentation and siltation, being strategic for the preservation of water resources in a watershed. According to article 3 of the Forest Code (Law No. 12,651/2012), these zones constitute Permanent Preservation Areas – PPA, defined as protected areas, covered or not by native vegetation, for the protection of water resources, soil, landscape, biodiversity, and ensuring the well-being of populations (BRAZIL, 2012).

Despite the legal predictions, the continental aquatic systems are the most impacted by the pressure resulting from the disordered growth of cities and production processes (MARCON et al., 2013; RIBEIRO, 2015). The intense occupation of riverbanks, especially when inserted in the urban and peri-urban landscapes, has been responsible for environmental degradation, resulting in increased deforestation, erosion, siltation, soil compaction and water quality compromise, with consequence for the ecosystem (FERNANDES et al., 2015; SANT’ANA et al., 2015; SOUZA; BULHÕES, 2015; FERREIRA et al., 2016).

However, article 296 of the Manaus Municipality Organic Law provides that the municipality may or not create ecological reserves or areas of relevant ecological interest. In the sole paragraph, Ponta Negra, the Bolivia Bridge, the Tarumã, the Tupé and Amarelinho beaches, on the edge of the Educandos neighborhood, as well as the Manaus streams are considered areas of ecological interest. The section dealing with urban planning specifies, in art. 234, that “the area of ​​Tarumã/Ponta Negra is designated as the Tourist Region of Manaus, and the actions of the municipality should be oriented to enable adequate infrastructure” (SILVA, 2005).

In addition, the region where the Gigante watershed is inserted has a great diversity of land and water use and occupation, and although it is part of the Tarumã-Ponta Negra Environmental Protection Area (SOUZA et al., 2018), it is susceptible to intense anthropogenic transformations, such as deforestation, irregular occupation and discharge of effluents and waste. According to Souza Júnior (2013), despite the large forested areas the Gigante river basin is the area of the capital of the Amazonas where the implementation of real estate developments is growing, especially in the lower course, where the areas are most valued.

In this context, recognizing that this area has great value for the population of Manaus, it is necessary to make efforts to understand, on a scientific basis, the impacts caused by anthropic dynamics in the Gigante river basin, subsidizing public policies for conservation, restoration and sustainable use of natural resources. Efforts in this direction should be based on an environmental diagnosis, which portrays and evaluates the current situation of the site, through surveys of components and processes of the physical, biotic and anthropic environment and their interactions (REIS et al., 2015; GONÇALVES et al., 2016).

In watersheds, multi-criteria methodologies can be used to support planning and decision-making actions quickly, without expending large expenditures on materials and equipment. According to Cremonez et al. (2014), there are several methods suitable for the environmental diagnosis, which can be employed individually or jointly. The most commonly used methods are checklists, matrices and interaction networks, and rapid evaluation protocols. The checklist is presented as a technique of low cost and complexity, capable of sensitizing society to the need to preserve water resources (BIZZO et al., 2014). The matrix and the interaction network are widely used within the environmental impact studies (CÂNDIDO et al., 2017).

Based on the above, the present study seeks to propose a perspective of environmental quality analysis, which relates the environment and nature in the low course of Gigante basin, Manaus-AM, through a joint approach of rapid assessment techniques. Thus, it is expected to verify the influence of the main sources of degradation, in order to subsidize the planning and management of this watershed, collaborating in the search for solutions to minimize the environmental impacts caused by human activities.

 

2 Material and Methods

2.1 Study area

Gigante River is one of the tributaries of the Tarumã-Açu Basin, located in the southwest of Manaus city (Figure 1). It covers an area of ​​21.84 km² and runs through the neighborhoods Tarumã, Redenção, Planalto, Lírio do Vale, Ponta Negra, Alvorada and Nova Esperança (ALPHAVILLE, 2008). The Gigante basin also belongs to the Environmental Protection Area Tarumã/Ponta Negra, established by Municipal Decree No. 9,556/08, which aims to protect the biological diversity and water resources of the area, to organize the process of human occupation and assurance the sustainable use of natural resources (MANAUS, 2008).

The low course of the Gigante basin covers the Ponta Negra and Tarumã neighborhoods, where the main of the 49 springs identified in the watershed are located. Near the outfall, there are high standard real estate developments and areas of exposed soil in the central portion (ALPHAVILLE, 2008). Dense urbanization characterizes land use and occupation in the Gigante basin, which is expanding in a hasty manner; forest remaining still in good condition; and extensive degraded areas with exposed soil (BRAGA et al., 2012). According to Prestes et al. (2018), between 2006 and 2017, there were significant changes in the basin's ground cover, with a reduction of 10.23% of vegetation cover and an increase of 13.16% of urban area. That is, there has been an increase in the waterproofing percentage of the basin, with potential damage to hydrological and ecosystem aspects.

As for the vegetal formations, the phytophysiognomies found in and around the Gigante basin are characteristic of Dense Ombrophilous Forest, Alluvial Dense Ombrophilous Forest (Igapó Forest – blackwater-flooded forest), Campinarana and ecotone areas (VASCONCELOS et al., 2016). Due to forest fragmentation, the basin presents erosive processes, silting of the contributing streams, alteration of water dynamics and surface water quality, grounding of springs, among other processes of degradation of the natural environment (ALPHAVILLE, 2008).

 

Figure 1 – Gigante river basin location map – Manaus/AM

Source: Elaborated by the authors (2019).

 

2.2 Environmental diagnosis

We conducted two visits to the study area to survey the primary data, collecting information about the area of ​​interest, through the pointing and photographic record. We applied the descriptive check-list method (SÁNCHEZ, 2013), listing, describing and analyzing the current condition of the area and identifying the main impacting actions observed.

After identifying the environmental impacts in the field, they were classified and characterized qualitatively according to the guidelines established by National Council of Environment Resolution No. 001/86 (BRAZIL, 1986), adapted by Oliveira et al. (2015), as indicated in Table 1. We have also organized a cause-condition-effect interaction network, allowing a brief and intelligible identification of impacts (direct and indirect) and their interrelationships (CARVALHO; LIMA, 2010).

The qualitative assessment was based on the interaction matrix from the analysis of the magnitude and importance of the identified impacts, with values ​​between 1 and 10, according to the technique derived from Leopold et al. (1971) and adapted by Silva (1994). This allowed a macroscopic analysis of the environmental impacts that occur in the area, and enabled the identification of the most significant impacts in each environment (physical, biotic, anthropic) analyzed.

The interaction matrix refers to a two-dimensional control listing, which relates factors to actions, supplying possible failures observed in the listing. According to Leopold et al. (1971), impacts have two main attributes: magnitude and importance, which, weighted, allow each impact to be valued. For Richieri (2006), the magnitude corresponds to the extensive measure, degree or scale of impact; importance refers to the significance of cause over effect. While the magnitude assessment is relatively objective or normative, as it refers to the degree of change caused by the action on the environmental factor, the importance score is subjective or empirical, since it involves weighting relative to the affected factor (CAVALCANTE; LEITE, 2016).

 

Table 1 – Parameters of qualitative impact analysis

Value	Positive (P)	When an action causes an improvement in the quality of the parameter.
	Negative (N)	When an action damages the quality of the parameter.
Order	Direct (D)	Result of a simple cause and effect relationship.
	Indirect (ID)	Result of a secondary action in relation to the action.
Space	Local (LC)	The effect is restricted to the place itself and surroundings.
	Regional (RG)	The effect spreads beyond the immediate surroundings.
	Strategical (S)	The component is affected collectively, nationally or internationally.
Time	Short Term (ST)	The effect comes in the short term.
	Medium Term (MT)	The effect is manifest in the medium term.
	Long Term (LT)	The effect manifests itself in the long term.
Dynamic	Temporary (T)	The effect remains for a certain time.
	Cyclic (C)	The effect is felt at certain times.
	Permanent (P)	Once the action is performed, the effects continue to manifest within a known time horizon
Plastic	Reversible (R)	After the action ceases, the environment returns to its original conditions.
	Irreversible (IR)	After the action ceases, the environment does not return to the original conditions at least in an acceptable time.

Source: Oliveira et al. (2015).

In this sense, the establishment of weights is an important factor for quantitative impact assessment, being a matrix technique (CREMONEZ et al., 2014). For the present study, an adaptation of Rocha et al. (2005), for the weighting of magnitude and importance values, as described in Tables 2 and 3.

 

Table 2 – Weighting of values for the magnitude attribute

MAGNITUDE (extension + periodicity + intensity)
Extension (Weight: 1 to 4) Size of environmental action or area of ​​influence.	-Small: +1 -Mean: +2 -Large: +3 -Very large: +4
Periodicity (Weight: 1 to 3) How long the effect takes to cease.	-Temporary (ceases when action stops): +1 -Variable (not known when effect ceases): +2 -Permanent (doesn’t stop with the end of the action): +3
Intensity (Weight: 1 to 3) Exuberance of impacting action.	-Low: +1 -Medium: +2 -High: +3

Source: adapted from Rocha et al. (2005).

Table 3 – Weighting of values for the importance atribute

IMPORTANCE (action + ignition + criticality)
Action (Weight: 1 to 4) Number of effects arising from the action.	-Primary (1 effect): +1 -Secondary (2 effects): +2 -Tertiary (3 effects): +3 -Nth (n effects): +4
Ignition (Weight: 1 to 3) Time lag between action and effect.	-Immediate: +1 -Medium term: +2 -Long term: +3
Criticality (Weight: 1 to 3) How critical is the cause/effect relationship.	-Low: +1 -Medium: +2 -High: +3

Source: adapted from Rocha et al. (2005).

 

3 Results and Discussion

Environmental diagnosis conducted in the low course of the Gigante watershed found, through the Check-list methodology, that the main impacting actions occurring in the area are the removal of native vegetation and the impacts resulting from it; the deposition of solid waste and the input of fresh domestic effluents directly into the body of water (Figures 2-3). The identification and qualitative classification of the main impacts are shown in Table 4.

Removal of native vegetation is mainly due to the implementation of real estate developments and supporting infrastructure, such as access roads, sewage treatment plant, pier, parking, river port and others. Costa et al. (2018), in the study of an urban watershed in Alfenas-MG, also found vegetation suppression by urban expansion. As explained by Oliveira et al. (2015), the removal of vegetation exposes and weakens the soil. Giunti et al. (2014) add that without the protection of litter vegetation and organic matter, there is a change in all ecosystem dynamics between the vegetation-soil-water interfaces, in addition to the loss of soil particle stability, exposing it to erosive processes, which will culminate, consequently, in siltation and compromising the quality of water bodies.

Deforestation in riparian areas also weakens the natural barrier function of these zones. This causes pollutants, contaminants and solid waste deposited near the stream to be carried by runoff to the riverbed, causing changes in water quality by increase in nutrient input. The release of fresh domestic effluents in stream, quite common in the analyzed section, contributes greatly to the increase of nutrients in the aquatic environment, which may lead to the process of eutrophication of the water body (SOUZA et al., 2016).

In addition, the emergence of exotic species in the analyzed riparian zone is another negative impact resulting from the removal of native vegetation (e.g. Megathyrsus maximus (Jacq.) BK Simon & SWL Jacobs, Dieffenbachia seguine (Jacq.) Schott, Ricinus communis L., Urochloa sp. P. Beauv., Leucena leucocephala (Lam.) From Wit.). The presence of plants considered exotic directly affects the germination of seeds of native species present in the soil, as well as the establishment of their seedlings, as they compete with each other for nutrients, light and water, being an obstacle to natural regeneration in these areas (MARTINS, 2015). The loss of the natural environment has as important consequences the retreat of fauna and the expulsion of dispersing and pollinating animals, essential in the process of succession and recovery of degraded areas (SOUZA et al., 2016; COSTA et al., 2018).

 

Table 4 – Qualitative characterization matrix of environmental impacts observed in the low course of the Gigante basin, Manaus/AM

Impact Actions/Impacts Found	Impact Actions Classification
	Value	Order	Space	Time	Dynamic	Plastic
Riparian vegetation removal	N	D	LC	ST	P	R
Soil exposure	N	ID	LC	ST	P	R
Soil compaction	N	ID	LC	MT	P	R
Siltation	N	ID	LC	MT	P	R
Presence of exotic vegetation	N	ID	LC	MT	P	R
Solid waste pollution	N	D	RG	ST	P	R
Effluent input	N	D	RG	ST	P	R
Erosion	N	ID	LC	MT	P	R

 

Figure 2 – Impacting actions identified in the Gigante River, Manaus/AM. Removing of native vegetation in the riparian zone (a) and depositing solid waste on the riverbed (b)

Source: Authors (2019).

Figure 3 – Disposal of domestic wastewater in the Gigante River, Manaus/AM (a) - (b)

Source: Authors (2019).

According to article 10 of the Manaus Master Plan, constitute actions foreseen in the Program for Protection and Valorization of Natural Environments and Watercourses, aiming at the protection of rivers and streams and their margins and the awareness of the population for their conservation and supervision, among others: curbing the release of polluting effluents and solid waste into rivers, streams and adjacent areas; raising awareness and integrating the participation of the population in the protection actions of watercourses, which could contribute to the healthy maintenance of water resources. Oliveira and Nunes (2015), by characterizing the environmental quality of water source in Linhares-ES, also proposed public policies for sanitation and land use planning.

The environmental impacts resulting from the primary action (vegetation removal) and their interrelations are structured in the interaction network (Figure 4). According to Tommasi (1993), this tool allows simple and intelligible visualization of impacts of all kinds in the physical, biotic and anthropic environments. The network of interactions contributes to the elaboration of restoration proposals, as done by Oliveira et al. (2015) in the city of Gurupi-TO; and in the definition of mitigating measures, as proposed by Souza et al. (2016) in PPA of the same city.

The absence of vegetation cover leads to soil compaction, which prevents water infiltration and intensifies surface runoff, which can lead to erosion and, consequently, sediment transport to the bodies of water. This sediment, when carried, may contain a certain load of nutrients, contaminants, heavy metals and other pollutants from solid waste, causing water pollution and contamination (SANTOS et al., 2015).

In permanent preservation areas, deforestation for the construction of buildings and roads aggravates environmental damage. Surface sealing, improper disposal of solid waste and domestic effluents constitute the main impacts resulting from urbanization over watersheds (LUCAS; CUNHA, 2007). In fact, in the studied area, several points of inadequate disposal of solid waste and domestic effluents were verified, which affect the quality of water resources and interfere with natural ecological processes.

 

Figure 4 – Gigante basin low course interaction network

Source: Research data.

The waterproofing, in turn, has a significant impact, including on the basin flows. Increased runoff from soil sealing will result in less infiltration and consequent reduction in groundwater recharge (GONÇALVES et al., 2016; LOURENÇO et al., 2016; MOTA et al., 2016). In regions with high rainfall, such as the Amazon, increased runoff in rainy periods intensifies erosive processes and siltation of water bodies. As shown in Figure 5, there is the presence of silting ready in sections of the Gigante River. Silva et al. (2018) also found silting points caused by the removal of vegetation cover in the riparian zone of the Formoso do Araguaia-TO streams.

It was also observed that in some upstream sections, where the vegetation cover is smaller, the amount of sediment changed the water color of the stream, leaving it with the characteristic coloration of whitewater rivers (Figure 5), although it is a river of blackwater. Rainfall the night before possibly intensified the carry-over of solid particles to the riverbed. These sediments decant along the stream, returning to a typical blackwater color as they approach the outfall. Studies such as Oliveira and Nunes (2015) also found increased turbidity at streams points with little vegetation cover in PPA.

The great landscape value of the Tarumã-Açu river basin, of which the Gigante River is a tributary, contributes to the advancement of real estate developments over permanent preservation areas, as well as the establishment of public and private moorages (Figure 6). The intense flow of people and vehicles compresses the soil on river banks and aggravates the erosion processes. Deposition of solid waste in these areas is also quite significant (Figure 7) and potentiates the risks of water pollution and contamination. This waste quickly reaches of the Tarumã-Açu River outfall and soon after then to the Negro River.

Solid waste pollution represented the most significant anthropogenic impact on the studied area, followed by effluent input, according to values ​​highlighted in the adapted matrix of Leopold et al. (1971) (Table 5). Souza and Silva (2015), Lima et al. (2017) and Ramos et al. (2017) also indicated solid waste disposal and effluent discharge as important negative impacts identified in their research.

 

Figure 5 – Gigante River stretches with silting points and alteration of water color, due to the amount of suspended material (a) - (b). The image on the left shows (in the lower right corner) the presence of Leucena leucocephala (Lam.) de Wit., exotic/invasive species

Source: Authors (2019).

Figure 6 – River port (a) and pier (b) installed on the Gigante River, Manaus/AM

 

Source: Authors (2019).

Figure 7 – Movement of vehicles and people on the river banks (a); and improper disposal of solid waste in port areas (b)

Source: Authors (2019).

Urban development around water bodies makes these environments sensitive to gradual anthropogenic transformations, with discharges composed of domestic effluents, heavy metals, solid waste, among others (LIMA et al., 2017). Improperly disposed solid waste is a source of contamination of water and soil resources; contribute to siltation and flooding processes; in the proliferation of disease vectors; and visual pollution (PIMENTA et al., 2016; COSTA et al., 2018).

Water pollution resulting from anthropogenic impacts can be point and/or diffuse origin. Point sources reach water bodies in a concentrated manner, as is the case of domestic effluent discharges identified in this study, having an easier control action. Diffuse pollution, on the other hand, occurs at random, along the length of the water body, such as the disposal of solid waste along the Gigante River. According to Von Sperling (2005), diffuse sources are difficult to identify and therefore require more complex control actions.

 

Table 5 – Result of applying the adapted matrix of Leopold et al. (1971) in the low course of the Gigante basin, Manaus/AM

Impact Actions/Impacts Found	Biotic	Physical		Anthropic
	Flora and Fauna	Soil	Water
Riparian vegetation removal	8	8	9	6
	9	8	9	8
Soil exposure	6	9	8	5
	6	9	8	6
Soil compaction	6	9	8	5
	6	9	8	6
Siltation	5	5	7	5
	7	8	8	7
Presence of exotic vegetation	6	6	6	5
	8	7	6	5
Solid waste pollution	9	9	9	9
	9	9	9	9
Effluent input	9	9	9	9
	9	9	9	9
Erosion	5	7	7	5
	7	8	8	6
Average	6,75	7,75	7,88	6,13
	7,63	8,38	8,13	7,00

Source: Research data.

 

Figure 8 – Aquatic macrophytes observed in the Gigante River, Manaus/AM. Eichornia crassipes (Mart.) Solms associated with Lemna sp. L. (a); Paspalum repens P. J. Bergius associated with Lemna sp. L. (b); Lemna sp. L. floating mats (c) - (d)

Source: Authors (2019).

It was possible to identify the excessive presence of aquatic macrophytes Eichornia crassipes (Mart.) Solms, Lemna sp. L., Paspalum repens P. J. Bergius (Figure 8). The growth of these vegetables is generally conditioned by the rich availability of nutrients. Blackwaters, however, have as their natural characteristic low production capacity and unfavorable ecophysiological conditions, due to their very low pH and low amount of mineral salts and nutrients (JUNK, 1979). Therefore, the high reproduction rate of these macrophytes may be a reflection of nutrient input due to the discharge of fresh domestic effluents and the deposition of solid waste, which may indicate depletion of water quality (OLIVEIRA; NUNES, 2015; RAMOS et al., 2017).

According to Kastratovic et al. (2015), aquatic macrophytes are often in contact with pollutants and, like all primary producers, react to changes in the quality of the environment in which they live, being good bioindicators of surface water condition, not only in an understanding of the current situation, but also in an assessment of trends in environmental changes over time and space. Lemna sp. L., for example, forms dense floating mats in eutrophic waters (VELICHKOVA, 2019), a condition found in the studied area (Figure 8).

 

4 Conclusions

Through the environmental diagnosis, we found the suppression of native vegetation on the Gigante River low course, including riparian zones, due to urban expansion with the implementation of real estate and support infrastructure, as roads and ports. The area constitutes a vegetative mosaic, formed by degraded and preserved areas. The removal of native vegetation triggered a series of second and more demanding impacts, such as soil compaction and sealing; erosive and silting processes; wildlife scaring; establishment of exotic species and others. Anthropic activities increases the deposition of hazardous waste and the input of domestic effluents into the stream, and enhance the risk to the environmental quality of the study area, especially with regard to pollution and contamination of water and soil; eutrophication; increase of disease vectors, due to the greater availability of favorable environments for reproduction of these organisms.

Thus, it is essential to comply with mitigation measures that promote the elimination of effluent emission and solid waste disposal; the protection and restoration of riparian areas, with the removal of invasive species and the conduction of natural regeneration and/or enrichment of the area. In addition, it requires effective supervision, monitoring and control of permanent preservation as regulated by the New Forest Code (Law No. 12,651/2012) and the public policies set forth in the Manaus Master Plan (Municipal Law No. 671/2002), Manaus Municipal Environmental Code (Ordinary Law No. 605/2001) and State Water Resources Policy (Law No. 3,657/2007).

 

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