Current Drainage Inlet Structure at 7th Ring Road and Doble Via la Guardia

Location of 7th Ring Road, Santa Cruz, Bolivia

Found Watershed Areas for 7th Ring Road Area

7th Ring Road Drainage Project
Santa Cruz, Bolivia
(resumens de los informes en Espaņol (PDF)

Houghton Hydro Group S.A.
David Peitz ,Survey Technician
Brian Greenhoe, Project Manager
Charles Schulz, CAD Technician

International Senior Design, CE 4990 & 4905 July 2005

Project Objective

To provide the City of Santa Cruz, District 10, with the best possible, sustainable, recommendations to solve the flooding problem on the 7th Ring Road.”

Design Parameters
Not enough right-of-way or slope for new canal to route 7th Ring Road Storm water to either 8th Ring Channel or 6th Ring Channel Minimally sloped topography Heavy sedimentation due to fine grained surface soil transport Heavy rain season Major budget constraints for maintenance

Background

This 2005 International Senior Design group partnered with District 10 of the City of Santa Cruz de la Sierra, Bolivia, to provide a design solution to the storm drainage problems on the 7th ring road. The city is set up with arterial concentric ring roads centered from the heart of the city. District 10 is in the southwest region of the city of Santa Cruz de la Sierra. Flooding during the rainy season, mainly November through February, creates standing overland water with depths reaching nearly one foot. This flooded area extends across the 7th ring road into the local inhabitants houses for weeks at a time. The flood water creates roadway, safety, and health hazards for the surrounding population. The Houghton Hydro Group S.A., was appointed to research and develop recommendations for the flooding problem on 7th ring road.

Existing 7th Ring Road Conditions

1. Outlet structure under Doble Via la Guardia (.75 m)
2. Doble Via la Guardia
3. Existing concrete ditch section
4. Gravel and lumber yard with access to both Doble Via la Guardia and 7th Ring Road
5. Existing earth ditch roughly the same size as the existing concrete channel.
6. Existing double culvert next to Tisu Street (2 X .6 m)
7. Low wide swale
8. 7th Ring Road
9. Small ditch
10. 17.5 Radial Road

Field Work and Data Gathered

Rain Season Flooding of 7th Ring Road

Group Members with Local Children of 7th Ring Road Area

Recommended Design

Proposed outlet to Doble Via LaGuardia drainage structure (2 x 1.4 m)
Proposed culvert for watershed D (1 x 0.75 m)
Aggregate and building material sales yard with access to Doble Via LaGuardia
Proposed concrete channel
Proposed culverts near Tisu Ave. for watershed C (2 x 1.1 m)
Proposed culverts for watershed B (5 x 0.6 m)
Possible location for gravel service road

Recommended Design Analysis

• The results of the hydrological analysis dictated a channel design capable of accepting run off from a 50 year one hour storm event. A runoff coefficient of .95 was chosen to reflect the saturated condition of the soils in the project area. The peak flow was found to be 6.51 cms (230 cfs).
• A ten year one hour design event was considered as a basis for channel design. The total estimated flow difference between a 10 and 50 year event was 1.42 cms (50.5 cfs) for the entire watershed. The difference in channel cross section was negligible. The ten year storm is standard design criterion in Santa Cruz.
• A bed slope of .001 was determined by topography and existing limiting conditions. Calculations on various sizes of channels confirmed that velocities would be within acceptable parameters.
  

Conclusion

• The advantages of a concrete channel are that it can be designed to carry the projected runoff and still provide adequate freeboard. A concrete channel will not be subject to bank deterioration or excessive vegetative growth which slows the flow rate and leads to sediment deposition further restricting the channel.
• The effective life of a earth ditch in Santa Cruz is estimated to be about two years before sediment causes the ditch to be non-functional. At this point the ditching needs to be completely reconstructed. Therefore earth ditching would not be sustainable for the city of Santa Cruz.
• The concrete channel was determined to be the best option in terms of the life of the channel, the ability to carry the design flows, the facilitation of maintenance, and the ability to self clean during peak flows if regular maintenance is neglected.
  

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