FLOOD08379

• County: Statewide
• Community: State
• Stream Name: All
• Basin: Statewide
• Title: Procedures for Determining Peak Flows in Colorado
• Date: 3/1/1984
• Prepared For: State of Colorado
• Prepared By: USDA Soil Conservation Service
• Floodplain - Doc Type: Educational/Technical/Reference Information

I

I

SECTION 3

I

HYDROLOGIC SOIL GROUPS

I

This section gives definition of four soil groups that are used in determin-
ing hydrologic soil-cover complexes, for estimating runoff from rainfall.

Definit ions

I

The hydrologic soil groups, according to their infiltration and transmission
rates, are:

I

A.

(Low runoff potential). Soils have high infiltration rates even
when thoroughly wetted. These consist chiefly of deep, well to
excessively drained sands or gravel. These soils have a high rate
of water transmission in that water readily passes through the~

I

\

B.

Soils having moderate infiltration rates when thoroughly wetted.
These consist chiefly of moderately fine to moderately coarse
textures. These soils have a moderate rate of water transmission.

I

I

C. Soils having slow infiltration rates when thoroughly wetted. These
consist chiefly of soils with a layer that impeded downward movement
of water or soils with moderately fine to fine texture. These soils
have a slow rate of water transmission.

I

I

D. (High runoff potential). Soils having very slow infiltration rates
when thoroughly wetted. These consist chiefly of clay soils with a
high swelling potential, soils with a permanent high water table,
soils with a claypan or clay layer at or near the surface, and
shallow soils over nearly impervious material. These soils have a
very slow rate of water transmission.

I

Source of Data

I

Local Soil Conservation Service field offices have soil survey data for
their respective areas. Much of this existing data was mapped with soil
symbols or with soil series names that may not be current. These symbols or
soil series names may be converted to current names with assistance from
respective SCS offices. The 1979 publication, "Soils of Colorado" has
current soil series names and hydrologic groups. This information is
included in Table S-2 of this publication.

I

I

I

I

I

3

I