---
title: "Lowest Value Polygon Topography Application Method"
slug: "lowest-value-polygon-topography-application-method"
description: "Read about the lowest value polygon topography application method to allow model bed elevations to be set to the lowest existing bed elevation. "
tags: ["2D modelling"]
updated: 2022-07-29T10:24:03Z
published: 2022-07-29T10:24:03Z
canonical: "help.floodmodeller.com/lowest-value-polygon-topography-application-method"
stale: true
---

> ## Documentation Index
> Fetch the complete documentation index at: https://help.floodmodeller.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Lowest Value Polygon Topography Application Method

2D solver includes a new application method for polygons, which allows  any model bed elevations within the polygon to be set to the lowest existing  bed elevation within the polygon.   This feature can be used to model  underpasses in embankments.   

For example, an underpass exists under and embankment whose crest is  at 10.0 mAOD and the base of the embankment is approximately 5 mAOD.   By  drawing a polygon over the area we wish to lower as well as some of the  surrounding, lower ground levels, the minimum value of 5 mAOD will be  applied to the whole polygon, lowering the embankment to allow flow through  the underpass.   

Polygons used for applying the lowest elevation must have an integer  attribute called lowest_val which must be set to a non-zero value.