An Ecological Assessment of the Louisiana Tensas River Basin Chapter 2 
The rankings based on the proportion of agriculture or 
urban land cover in riparian zones show similar patterns in 
the southern United States. The differences are more 
complicated in the western United States because 
nonforested vegetation may also be shrublands or grass¬ 
lands. 
Nationwide, the charts indicate that about 40% of the 
watersheds have riparian landscapes that are at least 70% 
forested, but an equal number of watersheds have very 
little forest cover in riparian landscapes. About 10% (200) 
of the watersheds have riparian landscapes that are nearly 
all agriculture or urban, and about the same number are 
almost completely undeveloped. 
Water quality is also related to larger patterns of land use 
over entire watersheds. For example, roads near streams 
affect water quality not only as direct pollution sources, but 
also because they represent paths for rapid runoff. The 
frequencies of roads crossing rivers were expressed here 
as the number of road crossings per unit river length in 
each watershed. This expression helps to adjust for 
differences in the total length of rivers between water¬ 
sheds. 
The map of watershed rankings for this indicator (Figure 
2.8) is complicated, and it does not closely resemble the 
national patterns found earlier when looking at land cover. 
The Tensas River Basin, like most of the Southeast and 
Midwest United States, has extensive road networks. Low 
lying areas are built-up to make roads thus changing the 
way water flows in the watershed. 
V) 
2E 
£ £ 
n 
890 
690 
400 
290 
Total Stream Length - Agriculture and Urban 
National Rank 
Quintile Data Range 
1 B < 3.4 
o 
10 2030405060708090 100 
Indicator Value 
Tensas River Basin 
15.7 -37.1 
37.1 -74.3 
>74.3 
