IAG 1999 Regional Conference on Geomorphology
Gloria Hotel of Rio de Janerio, Brasil, July 17-22, 1999
Abstracts - Sandra Baptista da Cunha and Antonio Jose Teixeira Guerra (Eds.)

DISCONNECTED AND DISCONTINUOUS GULLY EROSION DEVELOPMENT ON VALLEY HEADS: THE "COLÔNIA QUERO-QUERO " STUDY CASE

Paisani, J.C.1 and Oliveira, M.A.T.2

1 Universidade do Extremo Sul Catarinense, SC, Brasil
2 Universidade Federal de Santa Catarina, SC, Brasil
E-mail: paisani@cfh.ufsc.br, marcelo@cfh.ufsc.br


Discontinuous gullies are erosive features formed by independent incisions which may coalesce through time. Disconnected gullies are erosive features, identified frequently into valley heads, which incisions envolve disconected from the main drainage outlet. This work presents results of field experiments designed to investigate the main processes related to the development of a disconnected system of discontinuous gullies. The investigation followed three main axis:

A) development of water flow from the source area;
B) measurenent of water flow into the gully incision;
C) evolution of the gully system.

The flow from the source area was studied through tensiometric measurements, which enabled the study of saturated zones during a hidrologic year. Water flow into the gully incision was estimated by the use of na artesian retangular spillway with thin walls. The evolution of the gully incision was followed by the use of topographic measurements through time and by estimating global erosion rates. The main inputs, related to natural precipitation, was analysed by pluviometric and pluviographic data. Due to a strong "El Niño" event during the monitoring year, erosion rates are stronger then previous rates estimated to the area. "Potholes" created at the interface between disconnected incisions, presented the highest erosion rates. Although the experiment design failed to furnish a precise account of all mechanisms effective to the development of the erosive system, we hypothesize that the conjoint action of several individual mechanisms promotes the integration of discontinuous gullies into a disconnected gully.


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