Toward a dynamic representation of hydrological connectivity at the hillslope scale in semiarid areas

Hydrological connectivity has emerged as an effective means to understand and manage fluxes of water and transport of nutrients and sediment at the catchment scale, especially as fluxes are modified by changing climate and land use. However, hydrology has not yet adopted it as a unifying concept given uncertainties regarding different conceptions and gaps in understanding of how connectivity functions at different temporal and spatial scales. This paper outlines a conceptual model of hydrological connectivity for semiarid hillslopes and highlights the direction that future attempts to quantify dynamic hydrological connectivity might take. Rainfall-runoff analysis emphasizes the influence of antecedent moisture and temporal storm structure on hillslope-scale flood generation. Plot-scale field flume experiments demonstrate the spatial and temporal variability of flow resistance. The morphological runoff zone framework is presented as a method to upscale such results to the hillslope and incorporate the broader-scale issue of hillslope form. The need to design field experiments to inform attempts to model feedbacks between runoff depth and flow resistance forms the central argument of this paper. Patterns of infiltration and resistance across entire flow paths and their variability throughout a storm event are the key to understanding dynamic hydrological connectivity at the hillslope scale.