VJ 04 - VODHUD, VANJ: Flood Protection.
The right bank of the Vanjob River suffers from severe erosion and overtopping in times of high flow. The new village of Vahdat is at considerable risk of inundation and subsequent damage. Degradation of the existing embankment has also resulted in damage to an irrigation water pipeline resulting in reduced ability to effectively cultivate land.
In line with the project‟s originally conceived scope, to support the enhancement of climate resilience through the construction and rehabilitation of small scale riverine embankments, works will be carried out to strengthen the right bank of the Vanjob River, adjacent to Vahdat Village, and to protect it from future erosion. Protection works will be carried out over a length of approximately 1,200 m incorporating rock armor 0.8 m thick.
The precise engineering details of the optimal solution will be determined following detailed hydrological and morphological investigations at detailed design stage. However, local experience and design practice, for erosion protection works in Vanjob River, indicates that rock armor (0.8 m thick) is the preferred and most effective solution owing to the prevailing maximum velocities at peak flow times. Amour stone is locally available. The interventions proposed comprise;
- Rehabilitation and protection of the right bank of the Vanjob River, adjacent to Vahdat Village. Embankment length approximately 1.2 km.
- Protection to exposed face of re-constructed embankment and toe by large diameter armor stones
- Replacement of damaged irrigation pipeline, diameter: 250 mm, length: 250 m
The preliminary detail of the bank protection works is shown in the figure below. The works will entail construction of protection of two differing cross sections of approximately 600 m length each.
- Population: 80 households and their property
- Irrigated lands: 3 ha
- Road: 100 m
- Bridges: 2
- Medical center
- Shops: 3
VJ 03 - JHOVID, VANJ: Flood Protection
Successive flood events have brought large volumes of debris from upstream in the Bunai stream catchment. This has caused the level of the stream bed to increase; in turn reducing the free-board and the level of protection afforded by the existing embankments.
The existing embankments are also degraded and in need of protection from erosion and scour to the exposed face and toe.
The Bunai Stream is characterized by aggradation, owing to gravel sediment build up resulting in instability of the water course, as described for the Dahana Stream in Kulob District in section E. The rationale for the proposed interventions at Jhovid is, therefore, the same as that set out for the K04 Jerkala flood protection subproject. The following interventions are, therefore, proposed;
- Cleaning of mudflow channel, using bulldozer, approximate length 1 km
- Strengthening of mudflow channel banks with gabion mattresses. Fill material for the gabion mattresses may be obtained from the river channel.
- Restoration of the Dahana Stream Bed for a length of approximately 1000 m removal of accumulated gravel sediments.
- The precise planform of the channelization work shall be determined during detailed design by way of a hydro-morphological study. It shall, however, respect the natural meandering form that the stream current takes and excessive straightening of the water course shall be avoided.
- Partial rehabilitation of the existing flood and erosion protection to the right bank of the stream bed with gabion mattresses. The approximate total length of such works is estimated, from information gathered during site inspections, at 650 m. The precise locations within the reach shall be determined during detailed design.
- The project will support the acquisition of a suitable hydraulic excavator to be used within Jhovid Jamoat for maintenance of the stream bed and flood protection embankments.
After Project completion the population Bunai-1 and Bunai-2 villages and infrastructure will be protected from mudflows of the Bunai stream bed in the spring.
- Population: 50 households and their property
- Irrigated lands: 6 ha
- Medical center
- Shops: 2