DATA NEEDS AND DATA SOURCES
The purpose of this chapter is to identify data needed for calculations and analyses which will
lead to recommendations for highway crossings and encroachments of rivers. The types and
amounts of data needed for planning and designing river crossings and lateral encroachments
can vary from project to project depending upon the class of the proposed highway, the type of
river and the geographic area.
8.1 BASIC DATA NEEDS
The data, preliminary calculations, alternative route selections and analyses of these routes
should be documented in a report. Such a report serves to guide the detailed designs, and
provides reference background for environmental impact analysis and other needs such as
application for permits and historical documentation for any litigation which may arise.
8.1.1 Area Maps
An area map is needed to identify the location of the entire highway project and all streams and
river crossings and encroachments involved. The purpose of the map is to orient the highway
project geographically with other area features. The map may be very small scale showing
towns, cities, mountain ranges, railroads and other highways and roads. The area map should
be large enough to identify river systems and tributaries.
8.1.2 Vicinity Maps
Vicinity maps for each river crossing or lateral encroachment are needed to layout the
proposed highway alignment and alternate routes. There should be sufficient length of river
included on the vicinity map to enable identification of stream type and to locate river
meanders, sand bars, and braided channels. Other highways and railroads should be
identified. The maps should show contours and relief. Intakes for municipal and industrial
water, diversions for irrigation and power, and navigation channels should be clearly identified.
Recreational areas such as camping, picnic grounds, beaches, and recreational boat docks
should be identified. Cultivated areas and urban and industrial areas, in the vicinity of towns
and cities should be noted on the map. The direction of river flow should of course be clearly
8.1.3 Site Maps
Site maps are needed to determine details for hydraulic, roadway, and structural designs. The
site map should show detailed contours (1- or 2-foot intervals), vegetation distribution and type,
and other structures. The site map is used to locate highway approach embankments, piers
and alignments of piers, channel changes, and protection works. High water lines should be