Site Analysis - Project Planning and Management for Ecological Restoration - page 56

you determine the anticipated frequency, depth, and duration of flooding for your site based on
an evaluation of historic data and the hydrology of the watershed (Kondolf 1995). Dams occur on
numerous watercourses, large and small. Their impact on downstream lands is significant and
often unpredictable because water releases may not be regulated or consistent. Reliance on water
from controlled watercourses should carefully consider the operations of the water regulators
upstream.
Groundwater. Determining the depth to groundwater is particularly important when consider-
ing wetland and riparian habitats. Installing a series of water table measuring tubes (groundwater
observation wells) will enable accurate monitoring of shallow groundwater depths. Depending on
your location in the watershed, groundwater can fluctuate dramatically. Seasonal changes should
be determined because such information might affect how or when you plant to avoid using
supplemental irrigation, or at least determine how long you will require supplemental irrigation.
Understanding the fluctuations of the groundwater will determine the types and densities of suit-
able plants. In some situations, the groundwater is the result of flood events and the groundwater
normally fluctuates seasonally, with the plants able to drop roots quickly and follow the descending
water table. Often, there is not enough time before starting a project to collect the necessary data.
A survey of existing water wells in the vicinity may shed some information on the water levels and
water quality.
Surface Runoff. Examine surface runoff patterns to determine the need for erosion control
measures. Correcting erosion problems typically requires grading. If your design concept includes
earthwork, then you can evaluate various construction approaches to fix the problem; however,
for less aggressive projects, there are other techniques to consider, such as placement of rock, wat-
tling, or the use of plantings that can slow the water flow. Surface runoff may be unnaturally con-
centrated as a result of past activities. This may have affected the vegetation by changing species
composition, growth, vigor, and other microenvironment elements. Erosion problems commonly
can be handled successfully with vegetation and fiber blankets, coir (coconut fiber) or rice straw
rolls (wattles), or mesh fabrics typically nailed or stapled in place, or with various mulches held
in place with emulsifying liquids. Despite the recent advances in bioengineering material tech-
nology, not all situations can be solved by using vegetation alone. Particularly notable are those
situations where water is concentrated, either naturally or through drainage modifications, and the
water velocity or frequency is too high for plants to become established.
Water Quality. Water sampling on streams fed by urban runoff is essential to detect pollutants
coming from surrounding drainage areas. The levels may be sufficiently high to require some type
of treatment. A couple of options are immediately apparent: (1) consider designing a small wetland
to improve water quality (bioswale or retention basin) or (2) develop a program of educating the
landowners on how to control harmful chemicals and prevent them from entering runoff. The
former technique is becoming more widely used as the need for keeping waters clean gains world-
wide acceptance. The purpose of a restoration project may be simply to improve the water quality
of a stream, river, or lake because the changes in water chemistry will permit the reestablishment
of animals and plants previously eliminated from the body of water. A well-organized volunteer
group conducting water quality monitoring on the Delaware River, in northeastern United States,