Environmental Engineering Reference
In-Depth Information
Fig. 2.3 An annotated aerial photograph in the project file indicates that Molera Wetland is a
riverine wetland fed by a high water table and upland sources.
Outlines
show the areal extent of
vegetative ecosystems present in May 2011, when the photo was taken. Surveys can delimit the
true flow pathways and other details
number of sampling points, and resolution will all influence the resources needed to
complete the work and ultimately, the quality of the results.
Planning, and obtaining the appropriate resources will increase mapping suc-
cess. Prior to conducting a survey, we suggest you gather contextual data sets such
as U.S. Geological Survey (USGS) topographic maps (
http://topomaps.usgs.gov/
),
historical and recent aerial photographs, and regional digital elevation models.
Many of these are available through public databases often overseen by state
agencies in the U.S. This overview analysis can help determine the general surface
flow patterns that fill and drain the wetland. Review of historic aerial photos can
highlight temporal changes, such as gradual infilling of wetlands (sedimentation or
land use changes), ecological shifts (such as vegetation changes), and seasonality.
The broad view can help constrain the environmental questions and hypotheses, and
will serve to plan the survey collection. If resources are limited for initial data
collection, a quick tour through Google Earth (
http://www.google.com/earth/index.
html
) can be a useful starting point.
During the planning and preparation process, the following parameters can be
explored using the contextual data sets described above or in Google Earth. The
general center of the wetland can be described in latitude and longitude or in some
other coordinate system. The general setting can be described in terms of access,
land use, probable disturbances, position in the watershed, vegetative types, and
topography (see Fig.
2.3
as an example). The approximate elevation of the wetland
