Soil survey maps with engineering interpretations are available for a significant proportion of
the United States. They may be helpful in selecting layouts and assessing the suitability of fill
8.1.7 Climatologic Data
Stream gaging stations have been established on many streams throughout the United States.
However, there are some streams where either a gaging station does not exist near the project
site or a gaging station does not exist at all. In such cases, it is necessary to estimate flood
flows. These estimates may be based on regionalized estimating procedures or other
prediction models using meteorological and watershed data inputs. These meteorological data
are available from the National Weather Service (NWS) Data Center of the National Oceanic
and Atmospheric Administration (NOAA), and estimates of average conditions can be made
from rainfall data published by the NWS. Temperature records are helpful in making snowmelt
estimates, and wind data are helpful in making wave height estimates on rivers, lakes and
reservoirs as well as for coastal areas.
8.1.8 Hydraulic Data
Whenever possible, sediment load data should be provided as auxiliary data for river analyses.
Bed-material load, suspended load and wash load data may be obtained for some rivers in the
water supply papers published by the U.S. Geological Survey, state engineers' reports, flood
control and other water resources investigation reports. Information may also be obtained by
direct sampling of the river.
Riverbed cross sections and profiles may be obtained with an ultrasonic depth sounder and are
helpful in sediment transport and backwater studies. It is also helpful to know water
temperatures. Direct measurement of flood flows should be made when historical records may
be deficient. Depth and velocity measurements need to be made at a sufficient number of
subsections in a cross section to determine total flow rate. Discharge measurements made at
various stages at a gaging site can provide data for developing a stage-discharge rating curve.
Observations of high water marks along the river reach should be made. Each high water
mark and relevant profile should be established. These are helpful in calculating historical
flood discharges. Also, stages achieved by ice jams at specific locations should be noted.
Records of the performance of existing bridges and other drainage structures should be
obtained. Data on scour at piers of existing bridges (or at bridges which have failed) in the
vicinity should be obtained. For bridges which have failed, as much information as possible
should be obtained relative to direction of flow (angle of attack) at the piers or embankment
ends. Flood duration, debris in the river, distribution of flows, and magnitudes of scour are
useful information. Historical records of damage to adjacent property and results of legal
actions brought about because of damage are useful information also.