River Dredging: When the Public Power Ignors the Causes, Biodiversity and Science

Abstract

The river siltingis usually solved by dredging the sediment deposited in its bed, employing many techniques. In dealing with a concrete case, the objective is to expose the technical criteria lack for the execution of such intervention, the impacts to the river, aquatic biota and its real need. Here aspects of the dissociation between consecrated understandings in the engineering and their mismatch with the ecological theories are presented. This work aimed to study urban floods, elucidating their causes, to propose measures and new technologies to deal with them, through programs and urban policies. The intention is to detail the causes of urban floods, understanding the factors involved and with that, discuss how the public power should proceed in what refers to the dredging. The main objective of this work is to stimulate the incorporation of urban rivers into ecological studies and to draw public attention to this issue.

Dredging on water bodies and margin interventions: effects on fish

“…Dredging on water bodies and margin interventions: effects on fish* for navigation, plumbing, and rectification (Smith et al, 2019), among other interventions, with considerable impact for the river and its biota, especially fish (Grantham et al, 2019).…”

“…One of the problems in urban rivers is silting (sediment entry); this process triggers a reduction in the depth and width of rivers, alteration of the bed, and all of its geomorphology (Taylor et al, 2008). As a result, it causes flooding (Grantham et al, 2019), impairs navigation, in addition to reducing habitat heterogeneity, and blocks fish migration routes (Smith et al, 2019).…”

“…Such interventions cause several changes on the river dynamics, negatively altering the physical, chemical, and ecological composition, and causing damage mainly to the fish communities and bentonic organisms (Oliveira and Mello, 2007). In migratory species, interventions caused by silting can obstruct the river, destroy spawning sites, and bury eggs and larvae; there is also the possibility that the disturbed sediment clouds are contaminated with toxic substances or heavy metals (Smith et al, 2019).…”

Assessment of Anwai river water quality using the weighted arithmetic water quality index (WQI) in Delta State, Nigeria

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Rivers play a critical role in establishing any nation's development goals and also on a global scale as they stimulate human and national wealth, civilization, and education levels while touching on all facets of the ecosystem and human endeavour (UN-waters, 2016;Smith et al, 2019). As a result, it is critical to ensure the suitability, use and acceptability of these scarce finite resources in terms of water quality standards and preservation of its core value uses are imperative.

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“…dation of freshwater bodies is disturbing, as poor or declining water quality results in the loss of essential goods and services (UN-waters, 2016) as well as a significant loss of needed foreign exchange (Oelsner et al, 2017). Rainfall, erosion, discharged effluents from industrial and agricultural processes, and indiscriminate fecal deposition, xenobiotics, and a variety of other hazardous anthropogenic activities will impact water quality, particularly in surface freshwater bodies (Smith et al, 2019;Iloba, 2021). There are a few unaffected rivers in Nigeria regardless of status and area due to the expanding dimensions (diversity) of water demands and usage.…”