An Ecological Assessment of the Louisiana Tensas River Basin Chapter 3 
The watershed pattern of human use in 1991/92 is re¬ 
flected in the subwatershed rankings over the region 
(Figure 3.6). The highest U-index value for a 
subwatershed is about 96.7%, which means that 96.7% of 
that watershed has agricultural or urban land cover. The 
lowest value is 38.9%, and the average value is 77.3%. 
Compared to the national human use maps in Chapter 2, 
this is a very high human use index. 
Roads 
Roads and other transportation corridors are designed to 
connect the human-dominated elements of a landscape. 
The network of roads in the Tensas River Basin permits 
access, commerce, and communication throughout the 
region. Roads are also important for connectivity among 
ecological communities. Sometimes roads restrict eco¬ 
logical communities, as in the case of animals that are 
unable to cross roads. Sometimes roads enhance 
ecological communities, such as for plant species that 
spread along disturbed roadsides. In some cases, areas 
remote from roads may better accommodate wildlife, e.g., 
Louisiana black bears. The influence of a given road 
extends for some distance, depending on such things as 
road size and surface type, traffic volume, and type of 
use. There are few places in the Tensas River Basin that 
are entirely free of their influence. 
According to the road maps used for this atlas, there are 
about 3,666 kilometers of roads in the Tensas River 
Basin. This data set (U.S. Census TIGER) includes all 
types of roads-interstates, U.S. and State highways, 
county roads, and city streets. This works out to an 
average of 125 meters of road per person in the region. 
It is no wonder that roads are one of the most important 
human features in the Tensas River Basin landscape 
today. 
Figure 3.7 illustrates the road network within the Tensas 
River Basin. It is immediately apparent, with the excep¬ 
tion of road concentration in the urban areas of Lake 
Providence, Tallulah, and Saint Joseph, that roads are 
uniformly distributed throughout the Basin. Figure 3.7 
also breaks out kilometers of roads by zone. 
Figure 3.6. 
Human Use (U) Index, Tensas River Basin. 
