APPLICATION OF ELECTROMAGNETIC INDUCTION FOR ESTIMATING THE INFILTRATION RATE OF STORMWATER BASINS

Stormwater management is crucial due to the rising frequency of extreme floods, which severely impact the economy and daily livelihood of rural and urban populations. Increasing urbanization and climate change are expected to intensify these risks. Stormwater basins are highly effective tools for mitigating flood hazards by temporarily storing excess stormwater and releasing it in a controlled fashion. They also aid groundwater recharge by facilitating stormwater infiltration during storage and release. In practice, soil type and infiltration rate are determined using double-ring infiltrometer tests, well permeameter tests, and infiltration basin percolation tests. However, these in-situ measurement techniques are limited in spatial resolution and time-consuming. This research applies a non-invasive, expedient, and high-resolution electromagnetic induction method to generate geophysics-aided high-resolution infiltration rate maps. The study was conducted over an experimental stormwater basin at the University of Mississippi, with two inlets and one outlet pipe. An empirical relation between electrical conductivity and infiltration measurements from the double-ring infiltrometer is established for a limited number of points. High spatial resolution infiltration maps are then generated using the established empirical relation and Green-Ampt model from high spatial resolution electrical conductivity measurements. The geophysics-aided infiltration rates and those from the double-ring measurements are interpolated with the ordinary kriging method. The geophysics-aided infiltration rates map demonstrated strong prediction with R² = 0.90, RMSE = 0.56, and ASE = 0.51,compared to the double-ring infiltration map. At steady-state conditions, the geophysics-aided mean infiltration rate of ~2.60 cm/h closely matched the results of the water balance model. The infiltration rates estimated from both approaches are used to estimate the total volume of infiltrated water and are compared to the infiltration using a water balance for several rainfall events. This study provides guidelines for geophysics-aided estimation of infiltration rates with higher spatial resolution thereby enabling more accurate designs of infiltration basins.

[This work was supported by the USDA under Non-Assistance Cooperative Agreement 58-6060-6-009.]