Runoff Group Ma, Struba, Cassandra Springer, Jalen Allen, Derek - - PowerPoint PPT Presentation

Runoff Group

Ma, Struba, Cassandra Springer, Jalen Allen, Derek Risch, Tal Margalit, Tiana Tran

• To assess and interpret rainfall runoff data from September

2016-November 2016 Manoa valley watershed using runoff modeling

Objective

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

soilsurvey.sc.egov.usda.gov

Methods: Hydrologic Soil Group

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 October to November Figure 7: Total estimated RO versus Stream Gauge. 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