Develop a Project Concept. When the project is conceived the goals of the project should be
carefully defined and several options to meet these goals identified. The factors discussed in
Section 9.2. should be considered when identifying design options. These options will be
refined as the project progresses, eventually focusing on one or two options.
Assemble Available Data. All available data should be compiled and checked. The data
checklist presented in Chapter 8 should be used as a guide. Data which is unavailable or has
periods of missing data should also be listed on the checklist. Missing data can be ranked
according to need (i.e., essential, nonessential and optional). Field programs designed to
collect the essential data could be implemented at this time, however it is recommended that
a field reconnaissance and evaluation be completed prior to implementing field programs.
The field reconnaissance will provide a clearer definition of the project and will influence the
types and quantity of additional data requirements.
Conduct a Field Reconnaissance. An initial field reconnaissance should be performed by a
small group of technical personnel. It is advisable that the group be multi-disciplined so that
geologic, geomorphic, hydrologic, hydraulic, alignment and highway constraints can be
identified. They should define the problems for each option and identify possible solutions to
each problem. Options which are least feasible should be eliminated. Detailed procedures
and check lists for a field reconnaissance that considers most geomorphic factors important
to river engineering analyses are provided in HEC-20 (Lagasse et al. 2001). The field
reconnaissance team should identify the most favorable options, recommend the types of
analyses which will be needed, and design field programs to collect specific data which will
be required by the analysis.
Collect Additional Field Data. Field programs should be designed to collect only data that will
be required to analyze and design the project. The field reconnaissance discussed previously
is an important tool for the design and implementation of efficient field programs. By
designing and implementing field programs after the field reconnaissance, the collection of
unnecessary data can be avoided, providing more time and funding for collection of essential
data.
It is also advisable that the field crews be supervised in the field by personnel who will be
directly involved in the analysis and design. These personnel should be completely familiar
with the types of data and the methods used to collect the data, providing an interface
between the field and the analysis in the office. In this way, the field work, analysis, and
design can be closely coordinated.
9.4 CONCEPTUAL EXAMPLES OF RIVER ENCROACHMENTS
This section discusses conceptual examples of river response to highway encroachments.
Sixteen hypothetical cases are tabulated in Table 9.1. Each individual case is identified in the
first column to show the physical situation that exists prior to the construction of the highway
crossing. In the following three columns some of the major effects (local, upstream, and
downstream) resulting from construction of a particular crossing are given. Only the gross
local, upstream and downstream effects are identified in this table. In an actual design
situation, it is worthwhile first of all to consider the gross effects as listed in Table 9.1 (Level 1
analysis).
9.8
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