GULLY EROSION CONTROL AND CATCHMENT MANAGEMENT … the NEWMAP Approach

A presentation

AT A 5-DAY SHORT PROFESSIONAL COURSE HELD AT THE SCHOOL OF CIVIL ENGINEERING AND GEOSCIENCE, NEWCASTLE UNIVERSITY, NEWCASTLE UPON TYNE , 30TH JANUARY – 3RD FEBRUARY

2017

by

Gladys Fayomi MIPAN

Environmental Safeguards Officer Edo state NEWMAP

OUTLINE OF THIS PRESENTATION

• Gully Erosion in Nigeria – How bad the situation is – Past efforts

• NEWMAP Intervention – Erosion and Catchment Management Investments

• NEWMAP in Edo State – Auchi Oshiobugie site – Intervention approach – Environmental safeguards – Lessons learnt

• Moving forward

Gully Erosion Situation in Nigeria

• Southern Nigeria is affected by massive and expanding gully erosion.

• Estimated 3,000 gullies, which can be up to 10 km long with multiple fingers spreading through the rural or urban landscape.

• Up to 6 % of Nigeria’s land mass– severely degraded

Causes for gully formation a) Improper road design and

construction, b) Poor solid waste

management c) Destructive and

unsustainable land-use practices

How Bad is the Situation?

Past Efforts

• State and local governments are overwhelmed by the scale and complexity of the gully erosion problem

• Failed Palliatives

Nigeria Erosion and Watershed Management Project

The NEWMAP intervention is an 8-year multi-sectoral and multi-scale program with support from IDA, SCCF and GEF. It initially targeted seven southeastern States with acute gully erosion problems in Nigeria, but now with more states.

Specific objective of the project is

• to reduce the vulnerability to soil erosion in targeted sub-watersheds.

NEWMAP has four summarized components: 1. Erosion and Watershed Management

Investments; 2. Erosion and Watershed Management

Institutions and Information Services; 3. Climate Change Agenda Support; and 4. Project Management

Benefits: • Improved erosion management and

gully rehabilitation • Increased incomes for rural

households • Efficiency gains in public

administration

NEWMAP Approach

NEWMAP Component 1 Title Erosion and Catchment Management

Investments

Sub-components 1A Gully Rapid Action and Slope

Stabilisation

1B Integrated Catchment

Management

1C Adaptive Livelihoods

Main activities Stabilise severe gulley erosion sites

and conduct community-based

catchment interventions.

Main outcome Priority erosion sites rehabilitated,

and more secure livelihoods and

catchment services established.

• 1A Gully Rapid Action and Slope Stabilisation

• (i) emergency and temporary halting

of gullies and landslide management,

• (ii) complementary structural erosion and water management works, and

• (iii) preventive erosion control works as well as associated community

monitoring.

NEWMAP Approach contd…

1 B Integrated Catchment Management

- supports the development of a catchment management plan.

• Divide each large catchment into sub- catchments

• Guide investment priorities in soil and water conservation from upper to lower catchment

• Identifying stakeholders, interests and linkages

• Consultation with stakeholders

Selecting the Intervention Sites:

Criteria for Prioritisation of Sites

• State of gully erosion (very active)

• Very high risk to built assets including cropland and human life

• Cost effectiveness of proposed intervention.

• Risk to natural assets.

• Demonstrated local level participation and commitment.

Current Number of Sites selected: 13

Largest Site: Auchi Oshiobugie Gully erosion site

MAP OF EDO STATE

Auchi Oshiobugie Gully Erosion Site

length of about 2.4 km, maximum depth of about 25 -30m, with the top and bottom widths ranging between 70-120m and 17-108m respectively. The erosion gully has seven (7) gully fingers.

Auchi Oshiobugie Gully Catchment Delineation Map

Catchment area: 36.69ha for finger 1 (gully head) 11.13ha for finger 2 0.7401ha for finger 3 20.75ha for finger 4 233.8ha for finger 5 28.26ha for finger 6 7.997ha for finger 7

key focus for erosion control in the Project areas

• Managing the stormwater within the catchment area above the gully so as to reduce the peak flow quantity

• Safely route the stormwater that caused the gully to avoid any further erosion

• Dissipate the energy of the water once inside the gully

• Stabilized the gully side slopes and redirect local runoff so as to improve public safety and prevent further erosion of the surfaces

• Protect the base of the side slopes from under cutting

• Bio remediation to prevent further soil erosion while improving the landscape

• Water harvesting to capture rain water and run offs

Other Measures due to Geological findings

• Soil material is carefully protected against erosion and scour by use of riprap, geotextiles and graded filters.

• Water is guided away safely using channels with chute spillway and stilling basin to avoid soil degradation.

• Based on the soil shearing resistance and the gully slopes, safe margin of land to relocate structures and residents are to be determined.

• Loose soils to be reinforced with gully control structures.

Engineering Intervention Design- project site 1)Rectangular channel along the road to divert 60% of the runoff going into the gully.

2) Reclamation of the gully head and greater part of the gully by filling and compaction

3) Construction of chute channel to convey the flow from the culvert down to the stilling basin

4) Construction of Stilling Basin to collect the flow from the chute channel and the flood released to t5. Construction of Rip-Rap at the outlet of the Stilling Basin for outlet protection

he bed at a controlled velocity

6. Construction of Gabion weirs at every 50m intervals up to the wetland

7. Gabion gravity wall at the banks of the gully as embankment structures

8. Geotextile filters under the Rip-Rap and Gabion

…NEWMAP Approach

RENO MATTRESS MESH

GEOTEXTILE

BAFFLE BLOCKS

CHUTE

NEWMAP approach… • Construction of “check dams” participatory catchment management

planning

• Bioremediation

Restoration of access roads to streets

Before the intervention ongoing intervention

Stabilization of the gullies and construction of drainage channels.

Before the intervention Ongoing intervention

Restoration of access roads initially cut off

Before the intervention Ongoing intervention

Construction of Drainage Channels

Before Intervention After intervention

Restoration of degraded land

• Before

• Now

Environmental Safeguards

• Goal: to ensure that implementation processes during the execution of the proposed project activities are:

Environmentally-sound;

Encouraging community consultation and participation;

Enhancing social wellbeing and

Sustainability of the project.

Lessons learnt

• Engaging stakeholders is vital or project sustainability;

• Political will is a driving force towards project success

• Quality control is an essential tool for an effective project management

• Without team spirit and synergy a project may not achieve it full objectives

NEWMAP Team at work

World Bank, NEWMAP Task Team leader, Dr. Amos Abu in Edo during Project Launch

Former Governor of Edo State Comrade Adams Oshiomhole launching the project in Edo

World Bank, Federal and State NEWMAP team and contractors inspecting the project sites

The Edo State NEWMAP Team

Edo State NEWMAP team during the Presidential visit to project site

Moving Forward

• Project Monitoring continues

• Continuous stakeholders engagement

• Overcome the challenge of waste management in project areas.

THANK YOU FOR YOUR ATTENTION