Project Scope and Overview

After the meeting with our clients on February 6th, 2013, our group has had a deeper understanding of the project scope, the geological condition of the Botanical garden and the specific tasks we have to complete this semester. As we have mentioned before, the purpose of this project is to slow down the main water stream in Botanical garden, which will save water for emergency use and reduce water erosion to the bank. Research on the stream, its erosion and water recapture, has been ongoing and many senior students have already come up with some practical solutions. Based on the research done before, we are expected to provide more possible plans for the problem. Our main tasks are to analyze the geological condition of Botanical garden, to collect data of the water flow rate in some certain areas along the stream, and to complete a research paper for our final plan. The clients also suggested us to do a presentation after we finish the report. The specific time may be arranged after final exams. 

The following pictures were taken in Botanical garden.

Based on the geological condition in the area, we will use three main strategies for the project. The first one is to decrease the total energy head of water when it flows from upstream to downstream. This reduction can be achieved by increasing friction head or decreasing elevation head of water flow. In addition, we can also increase the cross section area of the stream so that the water velocity will drop with a constant flow rate.

Description of Possible Remediation Techniques

There are various techniques to decrease the velocity of the water stream. The choices that we have developed involves decreasing the volumetric flow rate, expanding the cross sectional area, and decreasing the flow speed directly. To accomplish these tasks in the real world, we have developed a number of feasible solutions to approach this issue:

1. Diverting the water stream by digging additional ditches that run parallel to the original ditch. This way, the volumetric flow rate that passes through each ditch is decreased to allow a slower flow speed. The ground water table at the location of the new ditches must be low enough to avoid a net gain in the total volumetric flow rate of the stream system.
2. Re-layer the stream bed with materials of rough surfaces, and construct rock weirs every 10 to 20 meters along the stream. This will increase the friction factor in the fluvial system and cause the water to slow down. Because the volumetric flow rate is held constant, water level will rise as a result. This consequence, however, is mitigated by the fact that the earth surface surrounding the stream is already high in elevation relative to the stream surfacebelow. As a result, we can increase the cross sectional area of the stream without needing to physically dig the stream wider. 
3. Expand the width of the ditch to directly manipulate the cross sectional area of the stream. The expansion should be dug symmetrically along the two edges of the stream. The depth of the expansions should be the same as that of the original ditch. With the cross sectional area expanded, the stream velocity should be expected to decrease.

Due to scheduling conflicts and time restraints, our group has yet to finalize a specific timeline for investigation of these ideas. However, we plan to conduct independent research over reading break, as well as consult Dr. Atwater when he is available, and look into principles governing the stream flow.

Each of these ideas has unique advantages as well as limitations. For example, although the addition of rock weirs to the streams will reduce the total flow energy of the stream while having minimal immediately negative effect on the area surrounding the stream, rock weirs are ultimately temporary structures as the water may erode around the rock weirs. Before our team selects one or two preliminary concepts to further investigate, we must determine which of these ideas will be the most effective in reducing the flow energy in the stream.

The efficiency of the concept will be rated based on how much energy can be removed from the stream at one single location and the number of locations available for the implementations of the design. The sustainability of the project is important as they will be needed as long as the streams exist, and maintenance of the designs should be taken into account. Although our project is small in scale, effects of our project on the local environment should still be considered. We have yet to narrow our project focus onto one single preliminary concept, but we will do so shortly, as we gather more information about possible impacts of each concept and the expected amount of energy each idea can remove from the stream.

We feel confident that a fix for this issue of stream erosion will be found with very little trouble. However the issue of erosion around the exit culvert is more serious and not as straightforward. Storm water overflows the bounds of the stream and the culvert is incapable of handling the necessary flow, causing massive erosion around the mouth of the culvert, undermining the embankment containing the culvert. It is not sufficient for us to only slow the water in the stream as the flow rate will remain the same. Inspection of the surrounding soils and planning for some type of overflow pool or stream will be our main focus throughout this project and the various data that has been collected concerning the stream will be looked at in the near future. After we have analyzed all of the relevant data we will begin to look for solutions to the overflow problem and possibly into water storage.

Now that we are well informed about the situation our next step will be to fix a time frame for our research and submit this as early as possible. Data such as stream flow-rates, soil analysis and any necessary surveying will be collected as soon as possible to enable us to start coming up with practical, efficient solution ideas.