fan-head trench

geology

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

June 26, 2026

Quick Summary

A fan-head trench is a geological feature formed when a river entrenches itself into the surface of an alluvial fan. This trench has a gentler gradient than the fan itself, becoming shallower as it extends down the fan. Sediment can be transported and deposited further down the fan within this trench than it would in a normal surface channel. The location of deposition on the fan can therefore be influenced by where the trench emerges onto the fan surface. These trenches can be temporary, with alternating episodes of trenching and filling, or permanent, especially if base-level decline causes significant incision.1

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

3 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

river
Fan deposits and depositional processes
…the fan apex produces a fan-head trench, which has a lower gradient than the fan surface. The trench is thus deepest at the apex and becomes shallower as it progresses down the fan; it eventually becomes part of the normal drainage system on the fan surface. This property is significant…
Read More
…the fan apex produces a fan-head trench, which has a lower gradient than the fan surface. The trench is thus deepest at the apex and becomes shallower as it progresses down the fan; it eventually becomes part of the normal drainage system on the fan surface. This property is significant…
Read More