Tag Archives: #stormwater

MERITS OF THE RECOMMENDED OPTIONS FOR STORM WATER MANAGEMENT AND CONTROL

By Engineer John Cee Onwualu (FNSE)

Storm Water Project in Delta State, Nigeria.

In my last post, I took a deep dive into the details of the findings and observations for Storm Water Management and Control Measures for Asaba, Warri, Effurun, and the environs.

It is clear that the topography of Asaba and its environs and that of Warri, Effurun, and its environs have similarities in their flood management and control approaches.

There were recommendations for optimal and efficient Pre-cast Open and Closed (underground sewers) concrete systems put forward for consideration and implementation for these project areas.

This article enumerates the merits to be derived from the use of these recommended pre-cast concrete structural elements of rectangular, square, and circular channels.

1) The use of precast primary receivers for the construction of the downstream channels to receive storm water discharges from the streets’ right-of-way will reduce the construction time required for evacuation of the current flooding menace that is being encountered in the environment, since non-functioning drains will now have discharge points.

Storm Water Construction at Effurun, Delta State.

2) There are savings in project delivery in terms of time, handling, and cost optimization during fabrication and execution of the project, since all these various types of channels with different operations will run simultaneously.

Construction of Drains at Okpanam, Delta State.

3) There is reduced construction risk to workers and passers-by during deep execution works since earth-moving equipment will be deployed for the placement of heavy precast concrete elements in deep excavations. This will improve the overall safety rating of the project.

Okpanam Drainage Construction, Delta State, Nigeria

4) There will be reduced exposure time to the excavated sections with the use of precast structural elements over cast-in-place concrete types, as the works are in built-up areas. This will improve the overall safety rating of the project.

Construction Work at Effurun, Delta State, Nigeria.

5) There is no need for long-exposed excavated trenches, as is the case with cast-in-place concrete, since smaller segments of work excavation are needed to place the precast elements.

6) The use of precast concrete structural elements will reduce in situ construction errors, which would create greater quality control on the project.

Storm Water Construction at Effurun, Delta State.

7) Finally, with adequate funding, the State government would complete the project within a short time, which would save her citizens the agony of economic and human losses occasioned with the hazardous and devastating flood water.

I hope that the state governments of different nations can take a keen look at the merits of these recommendations, and execute them where necessary.

Recommendations for Stormwater Management and Control

By Engineer John Cee Onwualu (FNSE)

Recommendations for Stormwater Management and ControlRecommendations for Stormwater Management and ControlRecommendations for Stormwater Management and Control

The details from the findings and observations of this study and design by Jefcon & Associates Ltd (Consultant) for the Stormwater Management and Control Measures for Asaba, Warri, Effurun and environs, showed that the topography of Asaba & its environs and that of Warri, Effurun & environs have similarities in its flood management and control approaches. 

Due to the nature of the terrains, the study on these cities and their environs have recommended optimal and efficient Pre-cast Open and Closed (underground sewers) concrete systems.  Therefore, the recommendations put forward for consideration and implementation for both project areas are that: 

1. The natural watercourses and downstream primary drainage channels should be considered as Priority No.1.  This involves clearing of the natural watercourses of weeds, waste, silt deposits and demolition of encroached properties along their paths; and construction of the downstream primary drainage channels that would receive flood water from the streets’ drains to these natural watercourses.  This will bring immediate improvements to flood water discharge on existing systems that do not have discharge points.

Recommendations for Stormwater Management and Control

2. Canalization of some of the watercourses with concrete mattresses, (See the figure above) is recommended as Priority No.2.  This involves the construction of 6m – 10m wide trapezoidal channels made with concrete mattresses. This will stop encroachment by property developers and create a definite demarcation of the natural watercourses. This will bring improvement on the existing systems while the construction of new infrastructures for more efficient and effective evacuation of flood water from the environment would be in progress.

Recommendations for Stormwater Management and Control

3. The need for updated Survey Maps for Asaba, Warri, Effurun, and environs by the Delta State Ministry of Lands and Survey is recommended as Priority No.3.  The presence of these maps will aid future planning and construction of infrastructural developments, as the lack of these maps has caused delays and increased project cost.

Recommendations for Stormwater Management and Control

4. With the implementation of items. 1 &2 above, the need to construct drainage channels in flood-prone areas is recommended as Priority No. 4. The construction of these street drainage channels (tertiary and secondary channels) in the identified flood-prone areas will create greater improvement in flood management and control of the environment.

Recommendations for Stormwater Management and Control

5. Government Ministries and Agencies in charge of urban development must stop approval of property developments on the natural watercourses and streets’ rights-of-way while identifying and demolishing those properties built on these mapped-out routes for quick evacuation of the flood water generated within the environment.

Recommendations for Stormwater Management and Control

6. Government Ministries and Agencies in charge of drainages must have a holistic maintenance and repair response plan with a motivated team.  This team should carry out a quick repair to damages on drainage channels as well as carry out periodic manual de-silting of the drainage channels.

Recommendations for Stormwater Management and Control

7. The State Orientation Agency and similar Agencies in charge of public enlightenment should do more at educating the populace on the hazards associated with the discharge of waste materials and blocking of drains and natural watercourses, as studies have shown that some see it as a normal way of living.

Recommendations for Stormwater Management and Control

8. The government should make it mandatory for property developers to create more areas for grassing and vegetation than stone or concrete interlocking pavements, as the use of the latter increases runoff in the streets.

In the next article, we take a look at the merits of these recommended options.

Flooding: A Global Warming Aftermath by Engr. John Cee Onwualu

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Climate change which is a direct effect of global warming has brought extreme weather changes to our environment, such as sea-level rise, more frequent rainfall with its associated flooding. The effects of these extreme changes have brought more flooding in our Cities, especially Asaba, Warri, Effurun, and Environs since they lie within the Niger Delta region of Southern Nigeria.

Despite these extreme weather changes from global warming, less attention is being given to the management, and control of stormwater by the government. The excess stormwater leads to the loss of agricultural farmlands, contamination of groundwater and rivers, and loss of lives and property of immeasurable values.

Today, due to the global climate change, Asaba, Warri, Effurun, and its environs are experiencing more months and frequent rainfall rather than the old known pattern of six months dry and six months rainy seasons. The effect on these cities and environs has defied the efficacy of existing drainage systems put in place by government and corporate bodies over the years. Hence, there was an urgent need by the government of Delta State to study and construct sustainable drainage systems for the management and control of Stormwater in Asaba, Warri, Effurun, and Environs.

This desire led to the Engineering Study and Design conducted in Asaba, Warri, Effurun, and Environs. Using interviews of locals, participatory meetings, and engineering surveys more in-depth knowledge of the flooding and causes was gathered.

The study looked at how overland drainages can be incorporated into nature-based gifts, such as Valleys, Waterways, and Rivers for the safe evacuation of the excess runoff generated from the environment.

Results obtained showed that improving the efficiency of these Natural Watercourses and Rivers would bring better management and control of the outfalls of both existing and new drainages into these Natural Watercourses. For this to be successful, the inhabitants must be aware of the environmental hazards associated with blocking of Valleys and Waterways with structures and dumping of waste materials into Storm Sewers and Drains, which would create blockages for the efficient evacuation of the Stormwater generated from the Environment.