Lake Livingston and Wallisville Lake affect salinity in Trinity Bay? If large volumes of water are 
transferred from Toledo Bend Reservoir and the Sabine River to the San Jacinto River drainage area 
as municipal and industrial water for Houston, how will the increased flow of wastewater discharge 
affect the bay? Would a three-dimensional salinity model more accurately portray future salinity 
gradients; if so, would the difference between model outputs justify the substantial investment of 
time and funds required to develop and verify the three-dimensional model? 
Navigation Channels 
Galveston Bay is a drowned river valley that has nearly filled with sediment from the Trinity and 
San Jacinto Rivers and smaller tributaries. Averaging only 7 feet in depth, bottom sediments are 
highly susceptible to wind-driven wave action and shrimp trawling that increase turbidity. Current 
ship channel maintenance dredging, and proposed channel enlargement and subsequent mainte¬ 
nance dredging, threaten to substantially increase turbidity over broad areas simultaneously. 
Turbidity decreases the depth to which sunlight may penetrate the water and therefore may decrease 
the primary productivity that supports much of the food web. 
Two facts are certain. Dredging will continue to occur if Texas waterways are to remain open. 
Secondly, economic and environmental decisions relevant to dredge spoil disposal are currently 
being made without an adequate data base regarding the optimum ratios between habitats, i.e., 
emergent marsh areas, submerged grass beds, shallow-water and deep-water habitat categories. 
Historically, state and federal regulatory agencies have required that dredge spoil material be placed 
either in approved disposal sites at or above mean high water. In the Galveston Bay system, erosion 
and subsidence has resulted in the conversion of upland habitat into submerged habitat and the 
conversion of shallow-water habitat into deep-water habitat. Shallow-water habitats are known to 
be more productive than deeper waters. It may be beneficial to place clean dredged material into the 
bay system to convert deep-water areas into more productive shallow-water habitat and perhaps 
achieve a more balanced ecosystem. Conversely, the current practice of placing dredged material 
above mean high water may need to be continued. 
Information Need 
A comprehensive habitat analysis needs to be conducted to ascertain the historical versus present 
ratio of the various habitat categories in terms of acreage and productivity, i.e. emergent marsh areas, 
submerged grass beds, shallow-water and deep-water habitats, etc. An analysis of this sort could 
provide data that would be beneficial from both an environmental and economic perspective. What 
will be the effect of nearly doubling the ship channel cross section, from the existing 40 x 400-foot 
(16,000 square feet) to the proposed 50 x 600-foot (30,000 square feet) section, on bay salinity and 
flushing? What will a new 12-foot deep channel across Trinity Bay do to bay salinity? (See Appendix 
I.) What is the margin of error on the salinity model? What will be the effects of resuspending sediment 
contaminants? 
Loss of Shoreline Uplands and Wetlands 
The quantification of loss, or gain, of land caused by natural processes and human activities about 
Galveston Bay is a principal issue. The loss includes both uplands and wetlands. Land that is eroded 
returns to the bay and contributes to other principal issues, such as the geochemistry of the bay floor 
and sediment dynamics. While property losses measured in real estate values are an immediate 
concern to local citizens, the land lost to the natural system over many years provides better estimates 
of past and future losses. Shoreline monitoring of the Galveston-Trinity Bay System has demon¬ 
strated a shoreline retreat of 2.2 feet per year landward between 1850 and 1982, causing a loss of 8,000 
acres of land (9). Shoreline retreat has increased from 1.8 feet per year before 1930 to 2.4 feet per year 
since then. 
The principal natural processes that determine shoreline position are (1) changes in relative sea 
level, (2) waves from prevailing winds, (3) storm waves, including tropical cyclones and northers, (4) 
supply of sediment from streams, and (5) subsidence. Human activities that impact the relative 
positions of bay shorelines include (1) land fills, (2) riprap and seawalls, (3) size and orientation of 
dredged channels, and (4) subsidence caused by pumping water, oil and natural gas. 
The diversity and health of bottom-dwelling animals depends on the distribution of bottom 
sediment types and the turbidity, i.e. the suspension of sediments, in the water column. Sediments 
are the carriers of both nutrients and toxicants in bay systems. Certain sediment types, such as 
accumulations of dead animal shells or sand, are significant economic resources. Therefore, the 
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