455 



that the model be kept in operating condition for future uses. The Commonwealth 

 had invested over $400,000 in this experimental facility and VIMS scientists urged 

 oflBcials to retain it for continued use by the State in developing the important 

 James River Basin and by the communities and industries located along the 

 river. 



The model was saved. The Corps agreed to a program of joint financing and 

 use by both the Commonwealth and the Federal Government. The model is kept 

 on standby status and VIMS pays monthly rental of $300 to cover costs of main- 

 taining it when not in use. As it has worked out, the model has been in almost 

 •continuous operation since the Channel Study was completed in late fall of 19G6. 



REPRODUCES NATURE IN MINIATURE 



The James River Hydraulic Model is an experimental device used by scientists 

 and engineers to duplicate nature in miniature. One horizontal foot in the model 

 equals 1,000 feet in the river ; one vertical foot represents 100 feet. Four days in 

 nature are sealed down to one hour on the model ; a normal 12i^ hour tidal 

 cycle is condensed to only 7% minutes. 



A protective shelter houses the model to avoid local wind effects, dilution from 

 rain, and to allow uninterrupted operation in winter. The model is 550 feet long 

 and 130 feet across at its widest point. The toed is molded of concrete and covers 

 some 25,000 square feet. 



The entire James River Tidal Tributary from its fall line at Richmond through 

 Hampton Roads into the Chesapeake Bay and including 200 square miles of At- 

 lantic Ocean is formed in the model. Tidal portions of all major tributary streams 

 iire included: the Elizahebh, Nansemond, Pagan, Warwick, Chickahominy, and 

 Appomatox Rivers. 



Man-made obstructions that interrupt the river's flow are also built to scale in 

 the model. Replicas of existing piers, bridges, tunnels, and the U.S. Navy's James 

 River Reserve Fleet have been added to duplicate the physical effects of these 

 structures. 



Model Scales 



Ratio 

 Scale Model: Prototype 



Horizontal Distance 1 : 1000 



Vertical Distance 1 : 100 



Water Velocity 1 : 10 



Discharge Rate 1 : 1, 000, 000 



Volume 1 : 100, 000, 000 



Salinity 1 : 1 



Time 1 : 100 



Tides, currents, freshwater flow, saltwater intrusion, and sediment deposition 

 are simulated with known accuracy. An automatic tide control mechanism regu- 

 lates rise and fall of the water level by alternately filling and draining water in 

 the system. Variable copper "hydraulic resistance" strips duplicate bottom 

 roughness, and they can be adjusted to make currents behave as they do in the 

 river. 



Strategically located inflow devices regulate the amount of fresh water intro- 

 duced. Artiflcial sea water from a large supply tank is pumped upstream by the 

 simulated tidal action to imitate saltwater intrusion. Gilsonite may be introduced 

 at different points along the model bed to simiilate sedimentation and scouring. 

 Dyes may be used to study circulation and simulate introduced chemicals, sus- 

 pended particles and even, to a degree, planktonic organisms. 



Measurements in the model are taken with various instruments. Tidal heights 

 are obtained with stationary point gauges. Current velocities are measured with 

 miniature Price rotating cup meters. Salinity samples are drawn by vacuum into 

 vials through small intakes set in the model at various depths. Sediment grids 

 indicate where silt may be deposited. Time-lapse photography and fluorescence 

 detectors are used in dye diffusion and dispersal studies and in sedimentation 

 and circulation studies. 



Because the model reproduces, records, and measures physical factors with 

 known accuracy and precision, scientists and engineers can demonstrate existing 

 conditions of the river or any new condition induced by either man or nature. 



