Botanical Gardens Hydrology

Hydrology deals with the water flow and its variations with time. Rainfall greatly influences the outflow at the garden pool.

This Crane Creek tributary ("Dent Creek?") is about six feet wide and flows at about 6 feet in 22 seconds based upon chip drift measurements. The tributary meanders broadly as it enters the gardens from under the new metal pedestrian bridge north of the Student Union Building. The main Crane Creek flows at about 6 feet in 8 seconds and is about 14 feet wide. This tributary flows into Crane Creek at a wooden plank footbridge located across from the Columbia Apartments.

Wheel speed measurements are below.

  Annual Rainfall

 Annual rainfall in Melbourne, Florida averages 65  inches, falling primarily in June through September.

The USGS plot above shows the variations in nearby Turkey Creek over some two years. The variation is approximately 60 times. June through November shows the rainy season effect. Drought occurs from December through June.

  Drainage Area

 The residential community to the west of Country Club Road captures the rainfall in ditches that lead to the major ditch south of Dartmouth Ave., which enters Florida Tech through a double culvert under Country Club Road. During dry periods, the soil can absorb moisture and runoff is low. If a storm has saturated the soil, then the water runs off quickly, flooding downstream areas.

In flood conditions, the stream covers much of the bottom lands in this marsh. The flow can vary by as much as 9 to 1 over the year, with the spikes of thunderstorms accounting for most of the floods. In the moderate rainfall of 1.7 inches by the time of the photo, the patio was half-flooded in three-inch deep flow. This bridge has a few inches of air space while others upstream had none.

On Sunday, 2/27/2005, the day of the west Palm Bay tornado, the area north of Keuper Hall was flooded a few inches deep on both sides of the humpback bridge. Central flow appeared to be about 5 to 10 feet per second with a width of ~20 ft. This might be a volume of 300 to 600 cubic ft per second.

The water shown primarily passes to the east past a clump of bamboo, overflows the bank, and travels overland and well away from the serpentine channel. At a point some 100 feet downstream, it forms a natural waterfall some eight inches deep, falling back down the dirt bank into the stream channel.

  Trash Load

 The stream has branches, leaves, and palm branches in it. Other trash seen has been bottles, cans, trailer wheels, pillow filling, boards, balls, coconuts, oranges, grapefruit, and miscellaneous household discards. Residents west of Country Club road appear to dump unwanted items into the stream to get rid of them. This trash is more concentrated after the first rain in several weeks and will be the largest problem in keeping the wheel spinning freely and limiting overflows upstream.

  Measured Flow at Pool Area

 The flow over the dam is about 0.25-0.5 inch in dry weather and about 2-10 inches in rainy weather. In severe storms, the height may exceed 14 inches. The height of the wall cannot be increased as the walkways upstream would be flooded more than they are now. There is significant impoundment for at least 200 feet upstream, providing averaging of the incoming flow. In a heavy thunderstorm, the flooded width by the wooden bridge appeared to be over 100 feet wide, and turbulent flow caused swirling whirlpools.

  Crane Creek and Turkey Creek Flows

Crane Creek flows through the north side of the gardens just east of the Columbia Apartments. A USGS gaging station is located at Babcock St. on the east side of the bridge.

http://nwis.waterdata.usgs.gov/fl/nwis/dvstat?county_cd=12009&sort_key=site_no&group_key=NONE
&sitefile_output_format=html_table&column_name=agency_cd&column_name=site_no
&column_name=station_nm&column_name=lat_va&column_name=long_va&column_name=state_cd
&column_name=county_cd&column_name=alt_va&column_name=huc_cd&format=html_table
&date_format=YYYY-MM-DD&rdb_compression=file&list_of_search_criteria=county_cd shows the following for Crane Creek, which the Garden stream flows into.

USGS 02249518 CRANE CREEK AT U.S. HIGHWAY 1 AT MELBOURNE, FL

This looks like

As a cumulative distribution function, this looks like

The garden stream (Crane Spur?) likely is somewhat in proportion to Crane Creek, so a scaling factor might be found. The CDF curve above is a starting estimate. One might infer from the knee of the curve that the garden stream will be in flood 5% of the time.

Turkey Creek flows through the Port Malabar area and exits into the Indian River Lagoon near US 1. A major contributor is the C-1 Canal System, though this will be restricted as the water is forced to the St. Johns River to the west.

  Wheel Rotation Speed

The wheel rotates without load (other than bearing grease friction) with a peripheral speed proportional to the water flow speed. The concept of Tip Speed Ratio (TSR) used with wind turbines applies here as well. For a drag (no lift) device, the TSR is less than 1, and the waterwheel is perhaps 0.7 since the water strikes at perhaps 0.7 of the wheel radius.

The speed of flow depends upon rainfall rate, which increases the height of the pond. Some observed values are listed chronologically below:

For flow versus speed assessment, the observations are listed by increasing spillway depth below:

An early plot of performance shows a hint of speed with rain-caused spillway depth. As rainfall increases, the buckets will fill more and the increase in speed with depth increases.

During flooding on 8/4/2004, the wheel continued turning at 60 rpm. Water finally was running backwards over the wheel, which was then jammed by a large plant.

About 7/15/04, the wheel drove a bicycle air pump that aerates the pool slightly, and ran much slower than unloaded. On 7/22/2004, I removed the pump, since the continuous motion had worn it out the piston seal! On 7/27/2004, the pond was refilling after draining and spillway depth was about 0.4 inch.

Back to the Waterwheel page

Back to Frank Leslie's home page

GardensWheel/gardens_hydrology.htm updated 050301