Connectivity of overland flow by drainage network expansion in a rain forest catchment. Issue 2 (22nd February 2014)

• Record Type: Journal Article
• Authors: Zimmermann, Beate; Zimmermann, Alexander; Turner, Benjamin L.; Francke, Till; Elsenbeer, Helmut
• Is Part Of: Water resources research. Volume 50:Issue 2(2014:Feb.)
• Page Start: 1457
• Page End: 1473
• Publication Date: 2014-02-22
• Subjects: connectivity -- overland flow -- stormflow -- suspended sediment -- phosphorus -- drainage network expansion; Hydrology -- Periodicals; 333.91
• DOI: 10.1002/2012WR012660
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Soils in various places of the Panama Canal Watershed feature a low saturated hydraulic conductivity ( K s ) at shallow depth, which promotes overland‐flow generation and associated flashy catchment responses. In undisturbed forests of these areas, overland flow is concentrated in flow lines that extend the channel network and provide hydrological connectivity between hillslopes and streams. To understand the dynamics of overland‐flow connectivity, as well as the impact of connectivity on catchment response, we studied an undisturbed headwater catchment by monitoring overland‐flow occurrence in all flow lines and discharge, suspended sediment, and total phosphorus at the catchment outlet. We find that connectivity is strongly influenced by seasonal variation in antecedent wetness and can develop even under light rainfall conditions. Connectivity increased rapidly as rainfall frequency increased, eventually leading to full connectivity and surficial drainage of entire hillslopes. Connectivity was nonlinearly related to catchment response. However, additional information on factors such as overland‐flow volume would be required to constrain relationships between connectivity, stormflow, and the export of suspended sediment and phosphorus. The effort to monitor those factors would be substantial, so we advocate applying the established links between rain event characteristics, drainage network expansion by flow lines, and catchment response for predictive modeling and catchment classification in forests of the Panama Canal Watershed and in similar regions elsewhere. Key Points: Overland-flow connectivity occurs along an ephemeral drainage network Connectivity is nonlinearly related to catchment response The connectivity concept could be used for catchment classification