Overview: OptiSurface 1Way is a Surface Type in OptiSurface which can drain to one direction (1Way). This suits crops grown with furrows where the water needs to drain in one direction along the furrow to exit the field.  All furrows will have positive slope to one end.  An example application is furrow irrigated corn where water is added at the top end of the furrowed row and must drain out the other end.

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Example
An example application is a furrow irrigated field where water is fed using a polypipe from the top of the field and water can drain out to the lower end. 

The field is currently grown with dryland corn and the client is looking for ways to improve the yield by irrigating. It will be designed with furrows running north-south and is located on the NW corner of the field.

Significant ponding was shown on the Drainage Analysis but these will be fixed with OptiSurface 1Way landforming design.

Existing Topography

Existing Drainage Analysis

Proposed Topography

An OptiSurface 1Way Surface Type was used with main slope set at 0.086% to 0.172%. We have done some irrigation analysis that shows that varying the furrow slope by up to 200% doesn't significantly impact irrigation performance.  Additionally, the Max Cross Slope to Main Slope Ratio was set to 2 to reduce the risk of water over topping the furrows on areas where the cross slope is significantly higher than the main slope.

Field Long Section

Subzones were used to force water direction on the headland (polypipe pad) to fall in one direction (from west to east) as shown below.

Cut/Fill Map

Earthworks ended up at a very reasonable 105 yd3/ac.