Use of terraces to mitigate the impacts of overland flow and erosion on a catchment

Abstract

The paper presents the impact of a historical system of terraces constructed centuries ago to mitigate the effect of a steep slope on overland flow. Systems of this type were constructed in past centuries by land owners, who then ploughed the land and grew crops on it. They used stones collected from the local agricultural fields as their terracing material. The influence of terraces on overland flow was simulated using the KINFIL. The overland flow is therefore reduced by greater infiltration of extreme rainfall excess flows on the terraces, and the KINFIL model shows to what extent the system of terraces can mitigate the resultant flood and soil erosion. The Knínice locality in North-Western Bohemia, with seven terraces and six field belts between them, was selected as the experimental catchment area. The results compare hydrographs with N-year recurrence of rainfall-runoff time, where N = 10, 20, 50, and 100 years, and the hydraulic variables, e.g. overland flow discharges of a design rainfall, hydraulic depths, flowing water velocity, and shear stress. The comparison provides hydraulic results with terraces and without terraces. The contrast between the results with and without terraces shows the positive role of the system of terraces in protecting the field belts.

Keywords

• extreme precipitation
• infiltration intensity
• soil protection