Runoff Group Ma, Struba, Cassandra Springer, Jalen Allen, Derek Risch, Tal Margalit, Tiana Tran
Objective • To assess and interpret rainfall runoff data from September 2016-November 2016 Manoa valley watershed using runoff modeling
Descrip?on • Runoff : The flow of water over the land surface, in rills, in stream channels, and in rivers . (Giambelluca 2016) - Occurs during rainfall events - Soil is saturated to capacity
Why assess runoff? • Understand flow of water after rain event • Understand hydrologic soil groups • Watershed quality • Urban impacts
Methods: Hydrologic Soil Group soilsurvey.sc.egov.usda.gov
Methods: Hydrologic Soil Group
Methods: Curve Numbers
Methods: Daily Precip Aggregation Daily rainfall from September to November
Methods: AMC Curve Numbers Rainfall limits for estimating AMC (Ambient Moisture Conditions) (US Soil Conservation Service)
Methods: SCS Daily Runoff Estimate Soil Conservation Service (SCS) RO estimate and the stream flow
Methods: Baseflow Model
Methods: Temporal Disaggregation Equations (Grid): - Hourly Data: - (Precip. (hr)/Precip.(day)) x Baseflow/Runoff (day)) = Baseflow/ Runoff (hr) - Total Runoff: - (Baseflow (hr) + Runoff (hr)) = Total Runoff (hr)
Results: Total Estimated Runoff vs. Streamflow Figure 6: Total Estimated RO versus Streamflow from Figure 7: Total estimated RO versus Stream Gauge. October to November R^2 = 0.885
Results: Upper vs. Lower Watershed Figure 8: Upper (blue) and Lower (orange) comparison of precipitation Figure 9: Upper (blue) and Lower (orange) comparison of RO
Challenges • Equation is not 100% accurate • Many variables needed • Chance of human error • Theoretical vs reality
Discussion • The Stream Flow and the Es?mated RO closely match the rainfall events • The bo,om 2 graphs show that there is a correla?on between the 5-day/ baseflow average rainfall and the SCS es?mate
Discussion of the Upper vs. Lower Watershed Figure 8: Upper (blue) and Lower (orange) comparison of precipitation Figure 9: Upper (blue) and Lower (orange) comparison of RO
Discussion “In most humid regions, infiltra?on capaci?es are high because vegeta?on protects the soil from rain-packing and dispersal, and because the supply of humus [dark organic material, formed by decomposi?on] and the ac?vity of mircofauna create an open soil structure” (Dunne, Chp. 9) “Under such condi?ons rainfall intensi?es generally do not exceed infiltra?on capaci?es, and HOF does not occur on large areas of the landscape” (Dunne, Chp. 9) Unless its a residen?al area, which is covered in cement or has been developed, where there will be more flooding if the rainfall exceeds infiltra?on.
Resources Dunne, Thomas and Luna B. Leopold. Water in Environmental Planning . W.H. Freeman and Company, 1978 Giambelluca, Tom. Runoff [PDF format]. Fall 2016. Retrieved from GEOG 405 Website: h,p://climate.socialsciences.hawaii.edu/Courses/GEOG405/ index.htm
Ques?ons? Anyone but Tom can ask ques?ons... UHM Geography Department
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