HYDROLOGY 103 EarthCache
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Hydrology is the science that encompasses the occurrence, distribution, movement and properties of the waters of the earth and their relationship with the environment within each phase of the water cycle. (USGS)
A watershed is an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel. The word watershed is sometimes used interchangeably with drainage basin or catchment.
When the amount of rain, snow-melt or both within a watershed is greater than the capacity of the stream, water and sediment will spill out of the stream bed onto the adjacent low lying land which is known as the flood plain. Over the centuries, this sediment will pile up like sheets on the flood plain resulting in a thick bed of rich soil.
Many cities and towns have been built on floodplains for a number of reasons: access to fresh water; the fertility of floodplain land for farming; cheap transportation, via rivers and railroads, which often followed rivers; ease of development of flat land. The effects of floods are physical damage and property loss. A flood will also cause contamination of water and food supplies and disease. All which place human life at risk.
Hydrologists apply scientific knowledge and mathematical principles to solve water-related problems in society: problems of quantity, quality and availability. At this site you are the hydrologist in charge. You must calculate the watershed's capacity and potential downstream risk. At the posted coordinates you have an artificial pond with storage capacity for excess water runoff.
Hodges Village Dam consists of an earth-fill dam with stone slope protection (this is the posted coordinates); four earth fill dikes with stone slope protection; two gated rectangular concrete conduits; and a chute spillway cut in rock, with a 125-foot-long concrete weir. The weir’s crest elevation is 19 feet lower than the top of the dam. The Hodges Village Watershed (drainage area) is 31.1 square miles. Hodges Village Dam can store up to 4.17 billion gallons of water for flood control purposes.
To qualify as "finding" this EarthCache please complete the following tasks. As always, a photo is appreciated, though of course, not required.
1) Calculate the MAXIMUM depth of the potential pond (flood pool) from the top of the dam to the water's edge. (You can utilize your GPSr for this but will also need to make some estimation as the entire height of the dam cannot be accessed by foot).
2) ESTIMATE the distance from the waypoint "BOTTOM" to the surface of the water. On your walk down to the bottom count the linked logs that run parallel to the road
3) If the watershed was to received six inches of rain in a short period of time, CALCULATE what percent of the pond would be filled, assuming there is no significant immediate loss of volume from the pond.
4a) Changes to the upstream landform (in the creek bed) can be seen at way-point "bottom". DESCRIBE the condition do you see here?
4b) what other changes to the upstream and downstream landforms can be anticipated by erosion, weathering and deposition with the fluctuation of this pond?
Additional Hints
(Decrypt)
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