Simulating effect of channel changes on stream infiltration

We use a saturated-unsaturated flow model (UNSAT2) to study the effect of soil cementing and channel widening on infiltration and recharge in two idealized profiles along the Rillito River of southern Arizona. The channel sections associated with the profiles are 202-ft (61.6-m) and 326-ft (99.4-m) wide. A synthetic 10-yr runoff in the river provides head values for generating infiltration before and after bank protection in these two sections. Results from the two base simulations are combined to produce four additional cases. Soil cementing the banks of the river without widening the channel reduces infiltration and recharge by 15% for the 326-ft wide (99.4-m) channel and by 25% for the 202-ft wide (61.6-m) channel. Increasing channel width together with bank protection increases infiltration 25% for our two sections. Increasing channel width without bank protection, however, increases infiltration by 46% for our conditions. Channel narrowing with bank protection markedly increases infiltration rates, about 50% for the two sections.