# Depression

Localized pavement surface areas with slightly lower elevations than the surrounding pavement. Depressions are very noticeable after a rain when they fill with water.

- Canonical URL: https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/depression/
- Last updated: 2018-09-19
- Review: reviewed by licensed professional engineers on the previous Pavement Interactive site, where reviewers were not recorded by name

## Description

Localized pavement surface areas with slightly lower elevations than the surrounding pavement. Depressions are very noticeable after a rain when they fill with water.

![Depression in a parking lot.](https://pavementinteractive.org/wp-content/uploads/2009/04/Depression1.jpg)

![Depression in a parking lot.](https://pavementinteractive.org/wp-content/uploads/2009/04/Depression2.jpg)

*Figures 1 and 2.* Depression in a parking lot. Depression in a parking lot.

## Problem

[Roughness](https://pavementinteractive.org/reference-desk/pavement-management/pavement-evaluation/roughness/), depressions filled with substantial water can cause vehicle hydroplaning

## Possible Causes

Frost heave or subgrade settlement resulting from inadequate compaction during construction.

## Repair

By definition, depressions are small localized areas. A pavement depression should be investigated to determine the root cause of failure (i.e., subgrade settlement or frost heave). Depressions should be repaired by removing the affected pavement then digging out and replacing the area of poor subgrade. [Patch](https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/maintenance/hma-patching/) over the repaired subgrade.