Assessment of Hydrologic Alteration Metrics for Detecting Urbanization Impacts

Reid D Mcdaniel,Frances C O’Donnell

doi:10.3390/w11051017

Reid D Mcdaniel, Frances C O’Donnell

Open Access

https://doi.org/10.3390/w11051017

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Journal: Water	Publication Date: May 15, 2019
Citations: 13	License type: CC BY 4.0

Affiliation: Auburn University

Abstract

Urbanization is increasing rapidly and has the potential to alter the hydrologic cycle. It is uncertain if hydrologic alteration metrics developed for large-scale analyses detect the impacts of urbanization. This study tests the ability of two such methods, Indicators of Hydrologic Alteration (IHA) and streamflow signatures, to detect the effects of urbanization in two watersheds in the southeastern U.S.A. A hydrologic model (HEC-HMS) was used to simulate flows in ungauged upstream tributaries to determine if analysis of flow from a large gauged watershed detects urbanization effects on upstream tributaries. IHA analysis detected trends in time in the watersheds, but the results were the opposite of what would be expected as urbanization increased minimum flows, decreased maximum flows, and decreased flashiness based on the trend in time and comparison with an undeveloped watershed. IHA parameters were more sensitive to urbanization than streamflow signatures. Subcatchments that transitioned from low to moderate or high levels of urbanization had greater levels of hydrologic alteration than was detected at the watershed outlet. Analyses of stream gauge network data may underestimate the importance of urbanization as a watershed characteristic due to scale issues, the variable effects of water management, and the dynamic nature of urbanization.

Highlights

IntroductionBy 2030, it is expected that 84% of the U.S. population will reside in urban areas [1], with urban land cover expanding to three times its area in
Most land cover change over the study period was the conversion of area classified as forest or as pasture and hay to suburban/residential or medium intensity commercial classifications, representing urbanization
Indicators of Hydrologic Alteration (IHA) analysis was more effective than streamflow signatures in detecting trends in hydrologic parameters during urbanization in large gauged watersheds, though the effects detected for urbanizing watersheds were the opposite of what would be expected based on studies of smaller catchments

Summary

Introduction

By 2030, it is expected that 84% of the U.S. population will reside in urban areas [1], with urban land cover expanding to three times its area in. The increase in impervious area associated with urbanization alters the hydrologic cycle by decreasing infiltration and evapotranspiration and increasing surface runoff [3,4]. This can have negative impacts for urban communities and those downstream, such as flooding and reduced water quality [5]. Peak flows are expected to increase, and recession times are expected to decrease due to the reduction in travel time of water over impervious surface versus undeveloped land [9]. The low flows of some streams have been shown to decrease after urbanization due to the reduction in subsurface flows [10], though the effect of urbanization on baseflow is complex and may lead to increases or decreases [11]

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Conclusion