Rainfall does not need to cause widespread flooding to expose a drainage problem. A single intense storm can leave water standing in a parking lot, overwhelm a detention basin, erode a slope, or send runoff toward a neighboring property. These issues may indicate that a site drainage system is no longer performing as intended. 

A current drainage study can help developers, property owners, and municipalities understand how water moves across a site and whether existing or proposed infrastructure can manage it. At REGA, our civil engineering team evaluates grading, stormwater runoff, detention, drainage infrastructure, and erosion risks for developments throughout Nebraska and the Midwest. 

 

How Rainfall Patterns Affect Existing Developments 

Many existing drainage systems were designed using the rainfall data, land conditions, and development patterns available at the time. Since then, rainfall trends may have changed, surrounding properties may have been developed, and paved surfaces may have replaced areas that once absorbed water. 

The U.S. Environmental Protection Agency reports that heavy precipitation and flooding can overwhelm stormwater systems, increase runoff, affect water quality, and damage buildings and infrastructure. When a large amount of rain falls within a short period, water may reach storm sewers, culverts, channels, and detention facilities faster than those systems can manage it. 

These conditions do not always mean the entire drainage system has failed. However, they are signs that the site should be evaluated before the problem becomes more disruptive or expensive. 

 

Why New Development Changes Drainage Conditions 

Development changes how water interacts with the land. Rooftops, streets, sidewalks, and parking lots prevent rainfall from soaking into the soil. As the impervious surface increases, more water becomes runoff and may move across the site more quickly. 

A drainage study helps engineers estimate runoff volumes and flow rates, identify where water will travel, and determine how it should be collected, stored, and released. For planned developments, this information informs site grading, storm sewer design, detention or retention facilities, culvert sizing, and erosion-control measures. 

Drainage planning should begin early in the design process. Waiting until construction documents are nearly complete can lead to redesigns, permitting delays, conflicts with utilities, or the loss of otherwise developable space. 

 

When Should a Drainage Study Be Updated? 

An updated drainage study may be appropriate when conditions on or around a property have changed since the original analysis. Common reasons include: 

• A proposed addition or redevelopment will increase impervious surface 
• Recurring ponding, flooding, or erosion has appeared 
• Upstream development is sending more runoff toward the property 
• Downstream changes affect how quickly water can leave the site 
• A detention basin, culvert, channel, or storm sewer is no longer performing as expected 
• Current permitting requirements call for updated stormwater documentation 
• The original drainage calculations no longer reflect current site conditions or design criteria 
• A property transaction, insurance claim, or dispute requires a technical assessment 

For drainage failures, construction concerns, or property disputes, REGA’s investigative engineering team can evaluate stormwater drainage, flooding, erosion, grading, and related site conditions. 

 

How Drainage and Erosion-Control Planning Protects a Site 

Effective stormwater planning manages how runoff enters, moves across, is stored on, and leaves a property. Proper grading, detention systems, stabilized slopes, and erosion-control measures can direct and slow water while protecting soil, pavement, utilities, water quality, and neighboring properties. These strategies can also help projects meet local stormwater requirements. 

 

Plan for Long-Term Site Performance 

Drainage problems rarely improve on their own. Ponding, sediment buildup, and erosion may become more severe with repeated storms, while a planned development can create new concerns if runoff is not addressed early. 

REGA provides civil engineering services for commercial, residential, institutional, and municipal projects. If an existing property is experiencing drainage issues or a planned development needs a drainage study, contact REGA to discuss the site and next steps. 

 

Frequently Asked Questions About Drainage Studies 

What is a drainage study? 

A drainage study is an engineering evaluation of how stormwater enters, moves across, is stored on, and leaves a property. It may include runoff calculations, site grading review, drainage-area mapping, and analysis of storm sewers, culverts, channels, detention basins, and other stormwater infrastructure. 

When should a drainage study be updated? 

A drainage study should be updated when flooding, ponding, or erosion occurs; surrounding development changes runoff patterns; the property is expanded or redeveloped; or current permitting and design requirements differ from the original analysis. An updated study can help identify drainage problems before they lead to property damage, construction delays, or disputes. 

Can a drainage study help prevent erosion? 

Yes. A drainage study can identify concentrated or fast-moving runoff that may erode slopes, channels, outfalls, and other areas. Engineers can then recommend grading, stabilization, detention, drainage improvements, or erosion-control measures based on the site’s conditions.