Analysis of Changes in Runoff Due to Land Cover Change

Document Type

Conference Proceeding

Publication Date


Publication Title

Watershed Management Conference 2020


American Society of Civil Engineers

Publisher Location

Henderson, NV

First page number:


Last page number:



Land cover change is a source of hydrologic problems across the southwestern United States. This study investigates the effects of land cover change on hydrograph simulation. The study area is the Santa Clara Valley, California. The study employs HEC-HMS software to estimate the runoff rate. Percentage of grass cover and built up land were extracted using the National Land Cover Database (NLCD). Two scenarios were generated using a calibrated model of the watershed. The two scenarios increased the percentage of imperviousness by 5% and 10%, respectively, of each sub-basin from the base scenario. The base scenario was calibrated using a 2017 events. The model was validated using a 43-day rainfall event. Both calibration and validation values are within allowable limits. The study employs the Natural Resources Conservation Service (NRCS) curve number (CN) method to estimate the runoff rates. The land covers were represented by different curve numbers. The results were validated using discharge data of stream gage with a bias of 12.30% and NSE of 0.63. The analysis shows that a 5% (scenario 1) and 10% (scenario 2) increase in the percentage of built-up land increases the runoff rate by 8% and 22%, respectively, due to a decrease in infiltration. Consequently, the peak discharge, for scenarios 1 and 2, was 18% and 48% higher than the base scenario, respectively. Whereas, the time for peak discharge was 3 and 8 h earlier than the base scenario. This study is helpful for urban planners and watershed managers to understand the dynamics of land cover on surface runoff.


Validation; Watersheds; Runoff; Runoff curve number; Calibration; Hydrology; Water discharge; Hydrographs; California; United States


Water Resource Management



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