Chapter 15, Problem 1FQ

To determine

The possible reasons that make this terrain so intensely channelized.

Answer to Problem 1FQ

The presence of easily eroded earth materials and lack of vegetation make high drainage density. Much runoff is generated by the barren slopes that easily cult gullies in the erodible materials.

Explanation of Solution

The desert sceneries are typically dominated by landforms rather than vegetation. The evaporation and precipitation regimes of a desert climate cause sparse vegetation cover; due to the fact that most processes of weathering require water, it results also in low weathering rates. The moisture-retentive soil cannot accumulate on slopes due to low rates of weathering, insufficient vegetation that is required to break the force of raindrop impacts, and absence of a wide network of plant roots to provide a support to hold fragment of rock in place. As a result, the soil present in those areas tends to be thin, rocky, and discontinuous. The absence of a continuous cover of vegetation and soil provides a unique character to the landforms in deserts.

Much amount of rain that falls in the desert becomes suddenly surface runoff to accomplish fluvial geomorphic work in a surface condition that is characterized by very limited interception and low permeability. Since the ability to hold grains in place is less, the grains that are loosened as a result of weathering will be swept away in surface runoff that is produced by the next storm. The effects resulting from activity of running water are also extensively evident on slopes and also in bottom of valley even though the desert landscapes strongly reflect water deficiency.