# Importance of Hydrology in Civil Engineering

**Importance of Hydrology in Civil Engineering**

Critically important! As a civil engineer, I’m always analyzing how storm water will flow around a structure, through a pipe, or detained by a pond.

Examples:

- Developer wants to build a shopping mall, but his parking lot for the customers who will visit his shopping mall will increase the amount of storm water on his neighbors. His neighbor Awill be extremely upset when the increased runoff floods his house. Therefore, the developer’s civil engineer needs to design a detention pond to prevent the parking lot from flooding the neighbor.
- A town has problems with a river that floods. They hire a civil engineer to design a levee to contain the flood waters. The civil engineer does a hydrologic study to determine the size of the levees.
- A contractor builds a house, but before the town will allow the homeowner to move, they require the contractor to verify that there will not be any adverse drainage with the house. They hire a civil engineer to analyze the site.
- The town wants to improve a rundown neighborhood to bring in business and upgrade their tax base. There is major drainage problems in the neighborhood. A civil engineer is hired to find the best solution (in this case, a storm sewer) and size the pipes to carry the storm water away.

All of the above examples, except the levee, I was personally involved in. I had to conduct a hydrologic study to determine how much storm water I had to manage. Only then can I solve the actual problem.

You as a civil engineer have been asked to design the sewer system of a city.

(In laymen’s term designing means finding the diameter of sewer line.)

For designing any engineering structure, there are two conditions which we try to fulfill.

- It should serve the purpose with sufficient factor of safety.
- It should be economical enough to fit in the budget.

Best choice is to take smallest diameter pipe to cut the cost.

But small diameter pipe will get chocked if the inflow in the pipe is more than it can accommodate.

So, if we can know the amount of inflow which is going to come in the sewer line, we can find a minimum diameter so that it doesn’t get chocked.

By doing this our design will serve the porpose as well as we can reduce the costs to minimum.

Now, for knowing the inflow, you need to know how much water comes into drain during storm season.

For knowing the amount of water in the drain, you should know, how much rainfall happens in the city? Out of total rainfall what part of it reach into drain?

Answer to these question can be provided by an experienced **hydrologist** by doing mathematical modeling of urban storm water.

This is just an example. Civil engineer faces many problem related to water in various channels and hydraulic structure.

**Hydrology is one of the most useful science for civil engineers.**

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