Flood Mitigation Project Oshakati 2012-2013-2014
Flood Mitigation Project Oshakati AREAL PICTURES TOPOGRAP RAPHIC C PICT CTURE RES OKATANA OKATANA EKUKU ONGWEDIVA ONGWEDIVA OSHAKATI OSHAKATI OMPUNDJA OMPUNDJA
Flood Mitigation Project Oshakati FL FLOODI DING MAR ARCH CH 12 2009 12 2009 MAIN OSHANA’S 1 OKATANA ONGWEDIVA OSHAKATI MAIN WEST MAIN EAST OMPUNDJA OMPUNDJA
Flood Mitigation Project Oshakati 1 MAIN WEST MAIN EAST
Flood Mitigation Project Oshakati OKATANA BRIDGE MAIN WEST MAIN EAST
Flood Mitigation Project Oshakati SKY BRIDGE KANDJENGEDI BRIDGE MAIN WEST MAIN EAST OMPUNDJA
Flood Mitigation Project Oshakati FLOODI FL DING MAR ARCH CH 12 2009 12 2009 DI DIVE VERTION TO THE MAI AIN WE WEST OSHAN ANA 1 MAIN WEST MAIN WEST MAIN EAST MAIN EAST OMPUNDJA OMPUNDJA
Concept Master Plan Oshakati Ekuku relocation area OMUNGWELUME OKATANA EKUKU ONGWEDIVA RUACANA OSHAKATI OKAHAO ONDANGWA OMPUNDJA
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
Typical Cross Section Dike Type I: dike with 4 lane dual carriageway road
Flood Mitigation Project Oshakati Bridges OMUNGWELUME bridge1 OKATANA bridge2 ONGWEDIVA RUACANA bridge3 OSHAKATI OKAHAO bridge4 OMPUNDJA ONDANGWA
Bridges Typical layout
Flood Mitigation Project Oshakati Sluices
Sluices Typical layout
Sluices Open
Sluices Partial Open
Sluices Closed
Flood Mitigation Project Oshakati Storm water drainage: Preliminary layout of major drains Water supply canal & Siphon Sky Bridge Okandjengedi Bridge Bridge parallel to Sky Ompundja Bridge
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
Flood Mitigation Project Oshakati Deepening of the Okatana River System Deepening of the River 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 stream will be shaped from the dyke embankment on the Northern side of • Oshakati to the dyke embankment in the southern side Side slopes will be 1:4 and the river widths will be 40 to 60 meters, similiar to the • openings 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 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 offering 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
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