Dredging involves in an excavation  operation usually carried out partly underwater, in shallow seas or fresh water areas with the purpose of gathering up bottom sediments and disposing them at a different location. On a positive side, dredging is often used to keep waterways navigable. Historically, the origins of dredging are lost in antiquity. The first known dredgers were the Phoenicians (modern day Lebanese) who created a worldwide network of ports, using stable ships to carry out dredging activities in rough waters. With modernisation, dredging became more technical and purposeful. For instance, in the United States, several hundred million cubic yards of sediment must be dredged from waterways and ports each year to improve and maintain the nation’s navigation system and to maintain coastal national defence readiness.
In Nigeria, the dredging of the River Niger many years ago was the first success recorded after which many registered and licensed companies most especially in the oil rich Niger Delta carried out dredging activities in that region. In 2009, Nigeria started a vast operation to dredge the River Niger to enable boats carry goods from the Atlantic Ocean to remote villages. The government said it would bring communities together, secure the flow to hydroelectric plants and ensure “all-year-round navigability”.
In considering the  rationale for dredging,  the negative effect should be considered first because the processes of eutrophication, sedimentation and pollution usually lead to collection and passage of rough, dirty and heavily polluted water and these in turn give rise to environmental health, social and economic concerns. Consequently, dredging activities are carried out to help to reduce aquatic vegetation growth by lowering the riverbed below photic zone (the depth of water in a lake, river, sea or ocean, which is exposed to sufficient sunlight to allow photosynthesis to take place). This, in turn, will help in dealing with nutrient loading, increase the habitat of fishes and reduce the breeding ground for mosquitoes. The resultant mortality, morbidity, damage to property and public infrastructure are pronounced.
The river transecting the community is now observed to be full of debris, with blocked channels, and plants grown on the surface and along the banks of the river. These could have caused obstruction to the flow of water and subsequent flooding. In addition, some residents are in the habit of dumping refuse at the riverbank, and some industries do discharge their agricultural products and wastes in water. This would automatically have influence on physical and chemical component of the river water, as well as deleterious effect on surrounding. Over the years, various levels of Government in Nigeria had embarked on dredging of the major rivers with a view to ‘sanitizing’ the environment. However, environmental impact assessment report before the exercise may not be publicly released, but the negative impact of dredging activities on health and environment cannot be over emphasised.
Some of these health and environmental effects should be taken into consideration before, during and after the dredging process. Dredging process has potentials for increased prevalence of communicable diseases. Because of the filthy environment brought about by unplanned disposal of dredged materials and indiscriminate refuse dumping at these sites, there could be an increase in the prevalence of communicable diseases. These refuse collections contaminate the surface soil and underground water, attract breeding of houseflies and act as sources of occurrences of diarrheal diseases such as Typhoid and Cholera. The waste heaps also serve as breeding sites for mosquitoes and consequently increase the prevalence of vector borne diseases.
Such breeding sites have both indirect and direct impact on the epidemiology of malaria in the city and the health systems, especially in local communities such as Aleto in Eleme Local Government Area, where dredging is going on. It would be noted that Eleme is a malaria endemic area in Rivers State and Nigeria at large. Though dredging brings about an improvement in flow of water and its speed, it may lead to subsidence increase and change in pattern of the epidemiology of diseases associated with fast flowing rivers such as onchocerciasis .In other words, the potential change in land cover and land use because of dredging brings about variety of global changes affecting ecological systems and 10 epidemiology of disease.
Inadequate dumping of excavated materials from dredged sites blocks most part of the waterways, rivers and streams in communities, including Aleto in Eleme Local Government Area. It is therefore, pertinent to put the necessary mitigating measures in place such as steps stipulated by Environmental Impact Assessment and engage in sustainable land use pattern to pollute less and conserve more of our environment towards sustainable growth. This would lead to a reduction in community health risks and enhance better quality of life. Although, dredging may have both negative and positive effects, the ill effects on health and environment are enormous if not properly managed. Dredging and disposal of contaminated sediment can adversely affect water quality, aquatic and terrestrial organisms.
In addition, dredging may damage underwater piping toxic chemicals that may have adverse effect on the aquatic lives content. Before any dredging activity is carried out in any environment, the government should endeavour to carry out a pre and post dredging environmental, and health impact assessment on a continuous basis, with reports of such assessments communicated to appropriate authorities. The prevalence of flooding in Aleto through Agbonchia communities in Eleme Local Government Area is a case in point. It becomes a cause for concern as some  indigenes of affected communities such as Aleto and Abonchia  are calling on the Rivers State Government to come to their aid to stop the illegal activities of dredging companies in the area. The situation in Okulu River in Aleto Community and Agbonchia is a case in point.
Reports say, affected communities have written to relevant agencies without any fruitful response. It is estimated that about 500 meters from Aleto Community to the Eleme Bridge on East West Road have 10 dredging machines and the noise pollution and vibration generated by these dredging machines are  injurious to the people leaving in the neighbourhood. It is common knowledge that residents in the entire area complain of adverse effects on their buildings. It is important to call on the authorities to check the menace and safeguard the lives before it becomes too late.
The time to act is now.

Kiikpoye Inabo

Inabo writes from Port Harcourt.