As the rainy season draws near, we should have a retrospect to help us evaluate the level of destruction of lives and properties by flood in 2012 to enable us prepare for what lies ahead.
The year 2012 cannot be forgotten quickly in Nigeria especially with respect to flood disaster. From Kano to Adamawa,Taraba to Kaduna,Kogi to Anambra ,Lagos to Cross River, the story of flood disaster and its attendant destruction of lives and properties is the same.
The Lokoja -Abuja road which accounts for about 70% of traffic between northern and southern Nigeria was reported submerged for days trapping travelers. Even the Benin/Asaba road and river Niger Bridge are being threatened by flood. Many Nigerians have lost their homes and valuable properties to this flood menace. More than 76,000 victims of the devastating floods that hit about 200 communities in five local government areas of Anambra State were evacuated from their homes to relief camps in Onitsha and Nteje.
Plateau State in North central Nigeria has had a fair share of the disaster last year. Many lives and properties were lost to flood disaster in both the northern and southern senatorial districts of the state.
In July 2012 in Gangare, Tudun-Osi, Tudun Talakawa and Angwan Rogo settlements in Jos north local Government council Plateau State ,heavy downpour which lead to the overflow of river Dilimi washed away many houses, and farm lands. Many people were reported drowned.
One month later, precisely on the 10th and 11th of August 2012, there was very heavy down pour that lasted for several hours at the southern zone of the state. The torrential downpour generated a lot of Flood killing about thirty five people and washing away hectares of farmlands. Many bridges and road embankments were washed off.
The roads affected by the flood are as follows
i. Jos – Langtang Road
ii. Langtang – Wase Road
iii. Langtang – Lalin – tunkus – Shendam Road and
iv. Shendam – Yelwa – ibi in Taraba State Border Road.
1. AREAS OF DAMAGES ON THE ROADS
The various degrees of failures inflicted on the roads are as follows:
A. Washout bridges that are inaccessible were at the following locations;
1. Reinforced concrete bridge at CH 0+100 (Shendam Town Bridge) along Shendam – Yelwa – Ibi Teraba State Border Road,
2. Reinforced concrete bridge at CH 8+000 (Langtang Bridge) along Shendam – Yelwa – Ibi Teraba State Border Road,
3. Reinforced concrete bridge at CH 17+800 (Lalin Bridge) along Langtang – Lailn – Tunkus – Shendam Road
4. Barley bridge at CH 18+200 along Langtang – Wase Road
5. Barley bridge at CH 18+400 along Langtang – Wase Road
B. Embankment washout of Bridges that are accessible are at the following locations;
1. Reinforced concrete bridge at CH 162+200 (Dagkang Bridge) along Jos – Langtang Road
2. Reinforced concrete bridge at CH 170 +050 (Lohmak Bridge) along Jos – Langtang Road
3. Reinforced concrete bridge at CH 2+000 along Langtang – Lalin – Tunkus – Shendam Road
4. Reinforced concrete bridge at CH 10+900 alone Langtang – Lalin – tunkus – Shendam Road
5. Reinforced concrete bridge at CH 15+025 along Langtang – Lalin – tunkus – Shendam Road
6. Reinforced concrete bridge at CH 32+125 along Langtang – Lalin – Tunkus – Shendam Road
Sub-Standard Bridge of Reinforced concrete deck on masonry stone abutments and piers at CH 19+150 along Langtang – Wase Road
Road Embankment washout at CH 172+030 – CH 172+250 (Both Sides) at Reak Village
It was also gathered that un known number of corpses were picked up in villages around the affected areas in Lang tang South, Lang tang North, Shendam Mikang Wase and Quanpan local government areas of the state.
About 100 communities and over 1,000 houses were affected by the flood, the Shendam Total bridge, and many other bridges in the senatorial district have either collapsed or on the verge of collapse. Most of the roads affected are Federal roads,
Over 1,000 families across seven local government areas in Southern Plateau have been rendered homeless .The flood is considered the worst flood witnessed in 50 years..It was also gathered that about 200 hectares of farmlands were also washed away by the flood in Shendam local government council alone. Properties damaged were located within 50 – 200 meters from both banks of the river, before the bridge.
The flood was unleashed by three days of torrential rains causing rivers and streams to overflow on Shendam and Langtang North and South which were worst hit. Mikang, Quan Pan and Wase local governments were also affected.
The Shendam Bridge gave way on 14/08/2012 complicating the situation by cutting off access to the affected areas and the link between Plateau State and neighboring Nasarawa and Taraba States. The second bridge linking Shendam with Langtang through Tunkus and Mikang is also on the verge of collapse. The approach slab is already giving way. Should this bridge collapse, Shendam will be completely isolated from the rest of the state paralising all commercial activities that have to do with movement of goods and people.
The news of this natural disaster informed the decision of the Chief Inspector of Engineering Regulation Monitoring Inspectorate Jos Zone to summon all the Inspectors to tour and inspect all the affected bridges in Plateau South Senatorial district on Thursday 30th August 2012.to ascertain the level of damage to engineering infrastructure and report to the Council for the Regulation of Engineering in Nigeria [COREN] For the attention of the Federal Government of Nigeria.
1.1 INSPECTORS: The following COREN Inspectors participated in the tour:
1] ENGR SAM GYANG AUDU-FNSE, CHIEF INSPECTOR
2] ENGR OKEY EZEMA –MNSE—INSPECTOR/RECORDER
3] ENGR SUNDAY HYAT-MNSE–INSPECTOR
4] ENGR EMMANUEL J DASAT-MNSE–INSPECTOR
5] ENGR DANLADI BONKAT-MNSE–INSPECTOR
6] ENGR GREG GBADAMOSI-MNSE–INSPECTOR
7] ENGR GODWIN ODUKWE-MNSE—INSPECTOR
From the inspection we generally observed that Floods and lack of maintenance caused the bridges to collapse… Severe floods which according to the natives interviewed never occurred in the zone in the past 50years causing rivers and streams to overflow, picking up debris like trees, and parts of collapsed houses lead to the bridge collapse. When the river passed under the bridges, the high water level smashed the debris into the bridges destroying the bridges immediately, the weight of the piled up combined with the force of the flowing water pushing on it caused the cracks and bending of some of the bridge piles resulting in the failure witnessed..
As at now, the river bed in Shendam Total bridge area has gone as low as 4m below the foundation of the abutment support living the bridge hanging on the piles which have started showing signs of failure. [See photos]The river catchment has extended far beyond the size of the bridge hence the bridge structure is no longer adequate for the volume of flow resulting in washing of the embankment. A study by the American Society of Civil Engineers determined that 53 percent of all bridge collapses are caused by flood and scour
: Design Defect
There are bridges whose collapse was inevitable before the bridge was ever built. The fault lies not with the construction of the bridge, but the design itself. In the case of some of the bridges visited at Mikang, and Mban, the abutment supports were so short that it was easy for water to wash off the soil around the abutment resulting in collapse of the approach slab. The old bridge at Mban collapsed and acted as barrier to free flow of water which found its way to the abutment support that yielded easily to failure.
Poor maintenance is a difficult problem to diagnose in the wake of a bridge collapse. Many bridge collapses could have been prevented with more stringent inspection and maintenance routines, and lots of collapses that occur for other reasons are exacerbated by poor maintenance. When a bridge is designed, the engineers assume a certain level of maintenance that is necessary for the bridge to live out its intended lifespan estimated at about 120 years. Rusted parts must be replaced, drainage areas cleared, new coats of paint applied and reinforcements added if traffic levels have increased. The threatened bridge category can be salvaged now if Government can appoint Engineers to periodically inspect bridges to ascertain the level of maintenance required
The devastating consequence of flood disaster in Nigeria this year has created a challenge for Environmental Engineers, Civil/Structural Engineers to brainstorm on means of curbing this ugly trend .We need to plan for un-anticipated disaster, define water ways, and work with Government to enforce laws to safeguard water ways. An indebt study of the remote causes of this year flooding need to be carried out to enable government formulate policies to safeguard the country from this menace and prevent future occurrence..
Neighboring countries like Cameroun should be made to give ample notice before opening their spill ways to avoid the effect of dams like Lagdo dam in Cameroun. There is need for more dams in the country to take care of unanticipated flood. The dams can complement the efforts of the Federal Government on National Integrated Power Project in terms of additional power generation.
The global warming issue/depletion of the ozone layer which is considered as a major cause of the extraordinary heavy rains this year need to be revisited
Federal Government is advised to consider Civil Engineers [Environmental/water/Structural Engineers] while constituting Committees on flooding and ecological disasters, erosion control and land reclamation as these professionals are in the best position to assess the effect of flooding and erosion on Civil engineering infrastructure like roads,bridges,drainages etc.