Abstract
Abstract. There is little information in scientific literature regarding the modifications induced by check dam systems in flow regimes within restored gully reaches, despite it being a crucial issue for the design of gully restoration measures. Here, we develop a conceptual model to classify flow regimes in straight rectangular channels for initial and dam-filling conditions as well as a method of estimating efficiency in order to provide design guidelines. The model integrates several previous mathematical approaches for assessing the main processes involved (hydraulic jump, impact flow, gradually varied flows). Ten main classifications of flow regimes were identified, producing similar results when compared with the IBER model. An interval for optimal energy dissipation (ODI) was observed when the steepness factor c was plotted against the design number (DN, ratio between the height and the product of slope and critical depth). The ODI was characterized by maximum energy dissipation and total influence conditions. Our findings support the hypothesis of a maximum flow resistance principle valid for a range of spacing rather than for a unique configuration. A value of c = 1 and DN ~ 100 was found to economically meet the ODI conditions throughout the different sedimentation stages of the structure. When our model was applied using the same parameters to the range typical of step-pool systems, the predicted results fell within a similar region to that observed in field experiments. The conceptual model helps to explain the spacing frequency distribution as well as the often-cited trend to lower c for increasing slopes in step-pool systems. This reinforces the hypothesis of a close link between stable configurations of step-pool units and man-made interventions through check dams.
Highlights
A check dam is a small transverse structure designed mainly for three purposes: control water flow, conserve soil and improve land (Doolittle in Conesa-García and Lenzi, 2010)
Despite the fact that the model proved to be successful in providing insight into the key processes involved in gully control, it does not account for many phenomena occurring in more realistic situations, such as those derived from complex gully geometries, meanders, presence of pools, stones or weeds and sedimentation dynamics, all of which may have a strong impact on flow characteristics
The conceptual model has combined in a single framework different previous approaches related to hydraulic processes to explain the basic flow modifications that check dams produce
Summary
A check dam is a small transverse structure designed mainly for three purposes: control water flow, conserve soil and improve land (Doolittle in Conesa-García and Lenzi, 2010). One of its most common functions is to enhance sediment deposition, reducing the bed gradient and flow velocity in order to check soil erosion within a stream, such as a gully. Based hydraulic models have been used to evaluate flood regimes and the influence of channel geometry in ephemeral channels in arid regions (e.g. Merrit and Wohl, 2003) and may become a useful tool for contrasting the performance of conceptual models which aim to predict the free-surface water profiles in gullies controlled by hydraulic structures. Different alternatives have been proposed for determining the spacing between adjacent check dams and there is no single universally accepted criterion. The three criteria most commonly found in the literature are (a) the head-to-toe criterion, namely, the toe of the Published by Copernicus Publications on behalf of the European Geosciences Union
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
