Submitted to: Journal Hydrologic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2013
Publication Date: 6/1/2013
Citation: Kennedy, J., Goodrich, D.C., Unkrich, C.L. 2013. Using the KINEROS2 modeling framework to evaluate the increase in storm runoff from residential development in a semi-arid environment. Journal Hydrologic Engineering. 18:698-706. https://doi.org/10.1061/(ASCE)HE.1943-5584.0000655. Interpretive Summary: Growth and urbanization occurred rapidly in the American Southwest and is projected to exceed the growth of other regions of the United States in the future. Computer models used to predict the effects of urbanization on runoff typically account for the impervious areas (e.g. roads, roofs, driveways) but not the effect of changes in the soil’s ability to absorb rainfall in the constructed area (e.g. yards, common areas). In this study detailed hydrologic measurements collected in a residential development and adjacent natural watershed in southeast Arizona were used with a novel ARS watershed model (KINEROS2) to demonstrate that compaction of soils done for construction resulted in roughly a 50% decrease in the amount of water that can infiltrate into the soils. Because of this change, about 25-30% of the total runoff due to urbanization was caused by soil compaction with the remainder caused by constructed impervious areas. Overall, the urbanization resulted in a nearly 20-fold increase in runoff over the natural watershed. The study also validated the new KINEROS2 model “urban element” which simplifies how a sub-division can be represented in the watershed computer model. In recent years, the increase in runoff associated with urbanization in the Southwest has begun to be considered as a potentially renewable water source so it is important to accurately estimate the amount of this extra, manageable water.
Technical Abstract: The increase in runoff from urbanization is well known; one extreme example comes from a 13-ha residential neighborhood in southeast Arizona where runoff was 26 times greater than in an adjacent grassland watershed over a 40-month period from 2005 to 2008. Rainfall-runoff modeling using the newly described KINEROS2 urban element, which simulates a contiguous row of houses and the adjoining street as a series of pervious and impervious overland flow planes, combined with tension infiltrometer measurements of saturated hydraulic conductivity (Ks), indicate that 17 14% of this increase in runoff is due to a 53% decrease in Ks in constructed pervious areas as compared to the undeveloped grassland. Ks in the urban watershed identified from calibrating the rainfall-runoff model to measured runoff is higher than measured Ks but much lower than indicated by a soil texture–based KINEROS2 parameter look-up table. Tests using different levels of discretization found that watershed geometry could be represented in a simplified manner, although more detailed discretization led to better model performance.