Chapter 1. Introduction and Summary of
Ordinary High Water Mark Indicators
ROBERT W. LICHVAR AND JAMES S. WAKELEY
1.1
PROJECT BACKGROUND
Arid-land fluvial systems are critically important environments that provide
valuable ecological benefits to the Nation. Small streams and rivers convey
floodwaters and help ameliorate flood damage; maintain water quality and quan-
tity; provide habitat for plants, aquatic organisms, and wildlife; and determine the
physical characteristics and biological productivity of downstream environments
(Brinson et al. 1981, Davis et al. 1996, Meyer et al. 2003). Ephemeral and inter-
mittent streams dominant the stream types of the arid southwestern United States.
For example, in Arizona most of the stream networks--96% by length--are clas-
sified as ephemeral or intermittent (Beven and Kirby 1993). Arid stream systems
are located within montane, piedmont, or basin landscapes and have rough bed
surfaces that are related to the stream gradient and watershed lithology, slowing
the movement of water and allowing for water infiltration and recharge of