THE IMPACT OF NKISI AROLI GULLY EROSION, WHY IT OCCURS, AND HOW WE CAN TREAT AND STOP IT. LOCATION: NKISI AROLI, INLAND TOWN, ONITSHA, ANAMBRA STATE, NIGERIA, WEST AFRICA. By Honey Ibeziako, Onitsha Archivist
Nkisi Aroli Gully Erosion is a widespread and often dramatic form of soil erosion caused by flowing surface water. It consists of open, unstable channels that have been cut more than 30 centimetres deep into the ground.
Nkisi Aroli Gully Erosion is a result of the concentrated runoff from steep ground flowing into cleared drainage depressions, unstable soils in drainage lines, interactions of land use, climate change and slope. It occurs on many different soils and landforms in Inland Town, Onitsha, Anambra State, Nigeria.
PREPAREDNESS MEASURE:
The aim is to reduce the harmful effects of all hazards, including disasters. It is defines as an emergency as the state in which normal procedures are interrupted, and immediate measures need to be taken to prevent that state turning into a widespread disaster.
NKISI AROLI GULLY EROSION CAN:
1. reduce land available for future reserves, zoo, agriculture, real estate, generate sediment and increase flooding that affects fences, farms, roads, and culverts.
2. wash sediment into waterways and water supplies
3. speed up the rate of erosion by exposing subsoil
4. increase turbidity (cloudiness) and nutrient loads in streams, rivers, dams and ponds
make it more difficult to access affected land
damage underground utilities such as power and phone cables, and pipes.
CAUSES OF NKISI AROLI GULLY EROSION
Several factors make gully erosion more likely:
1. sparse ground cover caused by concentrated runoff from steep ground flowing into cleared drainage depressions
2. unstable soils in drainage lines
3. sodic or saline soils - sodic soils contain a large amount of sodium ions (salt) attached to clay particles
4. intense rainfall
5. increased runoff caused by low levels of vegetation cover
6. poor soil infiltration
7. unfavourable catchment shape
PREVENTING NKISI AROLI GULLY EROSION
The best way to prevent Nkisi Aroli Gully Erosion is to maintain good ground cover. Most Nkerosion is caused by occasional heavy falls of rain onto areas of poor ground cover.
In most cases gullies can be prevented by good land management practices aimed at maintaining even infiltration rates and a good plant cover. Strategies for preventing gully erosion include: maintaining remnant vegetation along drainage lines and eliminating grazing from these areas.
CONSTRUCTION OF DAM NEAR THE HEAD OF GULLY
A dam built near the head of a gully or in a gully may store a large part of the runoff. The storage of water behind a dam reduces runoff downstream, and the reduction in runoff may permit natural revege- tation to control erosion for a reason- able distance below the dam.
CONSTRUCTION OF GULLY PLUGS
Gully plugs, also called check dams, are mainly built to prevent erosion and to settle sediments and pollutants. Furthermore, it is possible to keep soil moisture due to infiltration. Depending on the topography, amount of precipitation, material and financial resources available, there are several methods to construct a gully plug. They have to be inspected regularly and any damages must be repaired.
ADVANTAGES BUILDING GULLY PLUGS
Water speed is slowed, which reduces erosion and prevents unwanted gully formation during a flood
No trench design required, just uses existing gully drainage pattern
Can assist recharge of shallow wells
Can reduce salinity in groundwater
Allows groundwater recharge and sediment to settle out (reduces sediment transport)
Cost effective – these dams can use locally available materials
ACTIONS THAT WILL PREVENT NKISI AROLI GULLY EROSION INCLUDE:
1. maintaining a minimum of 70% ground cover.
2. stabilising knickpoints (points where the channel slope changes sharply) and gully heads.
TREATING NKISI GULLY EROSION
1. Measures to stabilise gullies must be tailored to the catchment in which the gully occurs.
2. Rainfall, soil type, land use and catchment dynamics must all be considered.
IN GENERAL, THREE STRATEGIES ARE NEEDED TO REPAIR NKISI AROLI GULLY EROSION:
1. modifying the catchment to reduce or redirect runoff
2. stabilising gully heads, floors and walls with built structures, earthworks, vegetation or fencing
3. reducing stock access to watering points.
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Please, pray for the Creator of Heaven and Earth to end disasters and Gully Erosion in Onitsha n' Idu and to restore all that we have lost. Please, let us call Jesus Christ at time of trouble and He will answer us. Prayer is the key, and sustainable development program is the solution.
Thanks and best regards,
Honey Ibeziako
Onitsha Archivist
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