Oshakati 2012-2013-2014 Flood Mitigation Project Oshakati AREAL - - PowerPoint PPT Presentation

Flood Mitigation Project Oshakati 2012-2013-2014

Flood Mitigation Project Oshakati

AREAL PICTURES TOPOGRAP RAPHIC C PICT CTURE RES

OKATANA OSHAKATI ONGWEDIVA OKATANA OSHAKATI

EKUKU

ONGWEDIVA OMPUNDJA OMPUNDJA

OKATANA OSHAKATI ONGWEDIVA

FL FLOODI DING MAR ARCH CH 12 2009 12 2009 MAIN OSHANA’S

1

MAIN WEST MAIN EAST

OMPUNDJA OMPUNDJA

Flood Mitigation Project Oshakati

1

MAIN WEST MAIN EAST

Flood Mitigation Project Oshakati

MAIN WEST MAIN EAST

OKATANA BRIDGE

Flood Mitigation Project Oshakati

MAIN WEST MAIN EAST

OMPUNDJA

KANDJENGEDI BRIDGE

SKY BRIDGE

Flood Mitigation Project Oshakati

FL FLOODI DING MAR ARCH CH 12 2009 12 2009

1

MAIN WEST MAIN EAST

OMPUNDJA OMPUNDJA

DI DIVE VERTION TO THE MAI AIN WE WEST OSHAN ANA

MAIN EAST MAIN WEST

Flood Mitigation Project Oshakati

Concept Master Plan Oshakati

Ekuku relocation area

EKUKU

OSHAKATI OKATANA ONDANGWA ONGWEDIVA OMUNGWELUME RUACANA OMPUNDJA OKAHAO

Concept Master Plan Oshakati

Ekuku relocation area

Flood Mitigation Project Oshakati Terrain / hydraulic model

Flood Mitigation Project Oshakati Flood

Flood Mitigation Project Oshakati Principle of the protecting dike

Flood Mitigation Project Oshakati Phase1 – Protection dike / length 23,6 km

Type II. DIKE WITH 2 LANE GRAVEL ROAD Type I. DIKE WITH 4 LANE DUAL CARRIAGEWAY ROAD Type II. DIKE WITH 2 LANE GRAVEL ROAD

Type I: dike with 4 lane dual carriageway road

Typical Cross Section Dike

Flood Mitigation Project Oshakati Bridges

bridge1 bridge2 bridge3 bridge4

OSHAKATI OKATANA ONDANGWA ONGWEDIVA OMUNGWELUME RUACANA OMPUNDJA OKAHAO

Typical layout

Bridges

Flood Mitigation Project Oshakati Sluices

Typical layout

Sluices

Open

Sluices

Partial Open

Sluices

Closed

Sluices

Flood Mitigation Project Oshakati Storm water drainage: Preliminary layout of major drains

Water supply canal & Siphon Okandjengedi Bridge Ompundja Bridge Sky Bridge Bridge parallel to Sky

Flood Mitigation Project Oshakati Storm water drainage: Objective and Description

Objective The objective of this task is to develop an integrated storm water management plan for the existing town of Oshakati as well as the future planned town areas and thereby ensuring that the town will be protected from localised rainfall and flooding inside the dyke area Description Three levels of drainage infrastructure:

• Rivers which form the main drainage out of the town
• Major storm water channels which takes the storm water from the areas into the

river system

• Minor drains that collects from within the residential areas and streets and then

feed into the major drains All channels were designed as trapezoidal or rectangular and pipe culverts were used for any road crossings The design flood frequencies we used for the design of the different channels were as follows:

• Major drainage channels: 1:20yr
• Minor drains: 1:5yr
• Crossings and major structures: 1:50yr
• Rivers: 1:50yr

Flood Mitigation Project Oshakati Storm water drainage: Typical Details

Flood Mitigation Project Oshakati Deepening and lining of the Okatana River System

• The stream will be shaped from the dyke embankment on the Northern side of

Oshakati to the dyke embankment in the southern side

Flood Mitigation Project Oshakati Deepening of the Okatana River System

Deepening of the River

• Side slopes will be 1:4 and the river widths will be 40 to 60 meters, similiar to the
• penings at the Okandjengedi and Sky bridge
• The route of channel that will be cleared will be approximately in the centre of

the current Okatana river and the embankments will not be protected at this stage but it will be excavated and shaped to same levels and profiles as specified for the lining phase

• The objective of this phase is to achieve maximum reduction in the risk of

flooding within the limits of the newly proposed dyke by the deepening and shaping of the river

• The Sky bridge and the bridge parallel to Sky bridge will be demolished and

replaced with upgraded bridge structures. The culvert structure at the Ompundja raod will also be replaced with the same bridge structure as being built at Okandjengedi

Flood Mitigation Project Oshakati Lining of the Okatana River System

Lining of the River

• The objective of this phase is similar to the deepening phase but with the added

benefit of the embankments being protected against erosion and therefore

• ffering a permanent solution
• The extent of the lining will be from the sluice gate in the North to the two sluice

gates in the South

• The lining will consist out of a mixture of selected clay material, soilcrete and

reinforced concrete sections

• The reinforced concrete sections will be at the top and bottom of the

embankment with the soilcrete protecting the slopes and the selected clay material will be compacted in the bottom of the river

• The reinforced concrete sections at the bottom of the embankment will also act

as guides for future silt removal

40 t0 60m wide canal

Flood Mitigation Project Oshakati Lining of the Okatana River System: Typical Sections

Typical Left Bank Typical Right Bank Typical Retaining Wall

Flood Mitigation Project Oshakati Concept Master Plan Oshakati / area 53,7 km²

Modeling floods: current situation

Terrain elevation Data from existing bridges, culverts etc. rainfall, water levels, evaporation

Modeling floods: scenarios

Terrain elevation Data from new bridges, culverts etc. rainfall, water levels, evaporation

Flood 2011: comparison of flood extent

before dyke construction after dyke construction

Flood 2011: Comparison of flood extent