Hi, I need help regarding IPCC latest SSP scenarios for Victoria, Australia at regional scale (RCM) for research purposes. I would appreciate suggestions for any open source data/websites/organization, which I can use to download. Anyone who used these latest RCM data. Please share the source.

Thank you..

Hey everyone,

I am working on an interesting project and would really appreciate a second opinion to see if my approach is correct. I'm posting here because it's mainly a hydrology question, but it also involves HEC-RAS.

I won’t go into the exact project location, but I’ll be as descriptive as possible so you can understand my doubts. The task is to confirm or verify the 100-year flood storm results from earlier studies (which covered a much larger area than what we're now focusing on). The objective is to model a drainage channel that will protect a lot on the north side from a combination of sheet flow and channelized flow flooding.

I’ve built a 2D rain-on-grid model in HEC-RAS using the available data, including high-quality LiDAR, gSSURGO soils data, land cover/use data, and NOAA 24-hour precipitation depths, distributed using SCS Type II 24-hour storms. The project area includes two catchments that intersect the proposed channel. To capture the system's dynamics, I merged the catchments into a single 2D flow area and applied boundary conditions at their outlets. For downstream boundary conditions, I used a normal depth of 1% and 1.2% for the two catchments, placing these conditions far enough downstream to avoid affecting the area of interest.

The computational grid is 15x15 feet and I’m using the diffusion wave method with a Courant-controlled time- step.

The Issue:

The earlier study provided results but didn’t include much detail about the modeling approach, apart from Manning’s n values. For simplicity, let’s say their study estimated a peak flow of 900 cfs at the channel location. However, when I introduce all the layers—land use , impervious percentages, and infiltration (using the SCS method with Curve Numbers)—my model produces much lower flow, around 350 cfs .

The lower flow seems to be driven by the land cover and soil data: much of the area is classified as shrubland with hydrologic soil types A and B, and only small areas of type D soils. This results in low Curve Numbers (CNs) ranging from 33 to 45, which generate minimal runoff and high infiltration.

BUT —when I exclude infiltration layers, the model produces flows closer to their study's results (~900 cfs). This suggests that their study did not account for infiltration. While this is arguably the safer approach for estimating peak flows, it also leads to an overdesigned channel with a capacity about three times greater than necessary.

My Questions:

1. I drew a profile line at the planned channel's location and extracted the flow hydrograph from it. The plan is to use the peak flow from this hydrograph as the input for sizing the channel. The profile line extends across the entire northern edge of the lot to capture all incoming water. Would you recommend this approach, or is there a better alternative?
2. The project is in the USA, but I can’t find clear guidance on whether infiltration should be included or omitted for safety. Is there a standard approach in cases like this?
3. How realistic would it be to "calibrate" (not true calibration since there’s no observed data) to match their flow by adjusting parameters? For example:
   • CN values for shrubland (type A soils) can range from 33–45, but even using 45 doesn’t approach 1,000 cfs.
   • Could I justify assigning a percentage of imperviousness (e.g., 20%) to shrubland, even though it’s not truly impervious?
4. I’ve already increased Manning’s n to the maximum recommended values for the land cover, but it didn’t significantly affect the results?
5. Are there other techniques or adjustments I should consider for this predominantly shallow flow system, with limited channelized flow?

I’m attaching all the relevant data and figures for reference. Hopefully, it’s clear enough to follow.

Looking forward to your insights!

Two Catchments at the project location with outlet locations and location of the planned channel at the norther boundary of the lot (red line)

Rain on grid model depth map model results

Hydrograph with peak flow WITH Infiltration layer

Hydrograph with peak WITHOUT Infiltration layer

Infiltration SCS CN Map

Land Cover Layer

2D model with brakelines and profile line representing the planned channel

Soils Layer

24 hour rainfall modeling is the standard for estimating flood risk.

But who ever decided that a perfectly normal 24 hour rainfall distribution, at an intensity expected approx once per 100 years, is the right way to figure out how high the water will get for a 100 year recurrence interval?

Isn't this totally dependent on the local landscapes?

I guess the 24 our rule of thumb makes some since for rivers. It takes hours (or more) for surface water to get from upstream to downstream. But for more upland hydrology with short times of concentration... wouldn't higher intensity / shorter duration storms tend to produce higher water surface elevations?

I'm evaluating a flood study right now and am just kind of rolling my eyes at the thought that the 100 yr 24 hour storm predicted flood depths are representative of actual high water marks in upland hydrology settings.

Hello, I have to find some scientific reference over the attached Q500 Q1000 estimation equation from Q10 and Q100. I found a reference that says they are from Handbook of Applied Hydrology: A Compendium of Water-resources Technology, Ven Te Chow McGraw-Hill, 1964, but I couldn't find an online source the confirm it. If anyone has the book or name of the method that I can search, it is much appreciated. I only need validation or a simple photo of the method page. Thanks in advance.

https://preview.redd.it/2ghozmpsxo6e1.png?width=261&format=png&auto=webp&s=ae0fe183fefa434113701f51a055c029db8ee2f8

I was wondering which topic direction would be most suitable for increasing my chances of getting Hydrology & Hydraulics / stormwater / flood engineering positions in industry or state/federal government.

My topic proposals:

Hydrology: Hydrologic and Catchment Modelling, flood modelling, urban flood impact and risk assessment, urban flood forecasting and mitigation, rainfall bias, Monte Carlo method.

vs

Hydraulics: Culvert hydraulics - hydraulic performances of culverts, design and hydraulic geometry of culverts, flow capacity, scouring, energy dissipation, open channel flow.

I am starting a master’s coursework degree in civil (water) engineering in 2025 in NSW, Australia, that has a research thesis project component.

I am interested in the quantitative modelling aspects of both Hydrology and Hydraulics, but it seems like the supervisors are more specialized in one or the other.

Interestingly, at my university, there seems to be a lot more open slots for research thesis topics in hydrology, than in hydraulics.

I am open to opinions and suggestions. Thanks.

• Australian Citizen
• Australian BEng(Civil) Degree
• Master's degree duration reduced to 1 year, due to recognition of my BEng(Hons) degree.
• Like quantitative aspects of H&H Modelling
• Like the symbolic manipulation aspects of the equations in hydraulics: continuity equation, energy equation, momentum equation, Froude number, Manning's roughness n, critical flow depth etc.
• Liked modelling in HEC-HMS and HEC-RAS in undergrad subject.

Hi everyone,

I'm a final-year civil engineering student with an interest in water engineering, and I’m currently brainstorming ideas for my final year project. I’d love suggestions for topics or project ideas in areas like:

• Water resource management
• Hydraulic structures
• Sustainable water supply systems
• Coastal and marine engineering
• Innovative solutions for water-related challenges
• Or any other related to water engineering

I want a project that’s practical and impactful, and ideally, something I can complete within a semester or two. If you’ve worked on similar projects or have any ideas, I’d appreciate your input!

Thanks in advance for your help!

Hey there! Wanted to see if there were any other US government hydrologist here. I'm a recent graduate with a BS in Earth Sciences with research distinction in Ecohydrology and a minor in Hydrogeology. Right now, I'm working as a permanent seasonal hydrologic technician for a National Forest in Wyoming. Most hydrologist positions in the federal government require 30 credits of science courses, with 6 hours of differential & integral calculus (I have 10) and 6 credits of physics (I only have 5). I qualify for most GS-7 grade hydrologist positions with the exception that I am one credit short in physics. I applied to Oregon state's ecampus online program to take another physics class.

Any recommendations for certain types of physics that are best for hydrology? I've already taken the basic calculus-based intro class with mechanics, waves, thermodynamics, etc. I may just end up taking one of their more popsci courses because I don't feel like taking the exact same physics course again, and don't need to learn more complicated topics like those related to electricity/electromagnetism. Thoughts?

I am a second-year undergrad hydrology student looking to go the engineering route by getting a master's in water resources/environmental engineering and getting licensed as a professional engineer. I just got hired as a water resources engineering intern at a county water agency, which is appealing because I would love a career in federal/state agencies (the dream would be USGS, NOAA, USFS, etc.). I also just received interview offers for a few engineering and hydrology Pathways internships with USGS and NRCS that I applied to before receiving my job offer. Is it a good idea to interview even though I am very happy with my new job and likely will not be interested in moving forward with the other internships? Is it stupid to turn down pathways internships that could lead directly to jobs with federal agencies?

Looking for some direction here. Long story short - i'm involved in conversations regarding the development of a subdivision about 40 miles Northeast of Denver. The water data that I've seen so far in these meetings is largely point-in-time data: water depth, pressure, and chemistry from a few months of surveying this year.

I've heard no mention of past or predicted trends RE: inputs (direct infiltration from rainfall here) or historic monitoring well data. Do such things exist, and where should I find them? I'd love suggestions for open source data, pertinent published studies, etc.

For context, I have a farmer's working knowledge of water and was once cruising toward a geology degree before life steered me elsewhere, so digesting technical data is right up my alley - i just need to know where to start looking. If you happen to be in NW WA state I'd happily pour your coffee or beer and discuss. Cheers!

Global Engineering Firms - What is it like?

I’m a water resources engineer a few months away from licensure. I’m considering moving to a global firm for the opportunity to collaborate/work on global/abroad projects, and maybe in the future even apply to move abroad.

Anyone who works at one now (the ones I am looking at the most are Stantec, Black and Veatch, Tetra Tech, Burns and McDonnell, CDM Smith, Arcadis) what is it like?

Are the hours crazy? Does it feel like fair wages/benefits for what you do? Did you get the chance to work on abroad (non USA for me) projects/does your company have a good program for doing that? Overall, do you like it?

Things important to me are work life balance (which the amount of public projects in water resources normally allows for that, even tho I work at a private firm) and PTO. WFH is also a huge plus as my current and last firm didn’t offer that. I’m based in Charlotte, NC and almost have my 4 years experience. Any and all commentary appreciated.

Thanks!

We are a group of three ( beginner )students working on a project on flood modelling.The main problem we are facing is of work division. If one of us changes a geometry or a numerical value, then all of us will have to repeat the same thing in each of our laptops.We have very limited time for this project and this issue is not helping at all.Can someone experienced please provide a solution to this problem?

For example: for a large terrain with multiple tributaries, it would be too time consuming for one guy to draw all those breaklines.Even if one of us draws all those breaklines, remaining members will be unable to proceed with other works during that time as those breaklines are the prerequisites for further computation.This is just one example of the many issues we are facing regarding time-effective work division.The solution we would want is 3 of us drawing breaklines each for one tributary and then merging them and proceeding for further work.

Hello, I'm posting this to ask someone that have had similar issues with the reading of certain levelogger data. I'm doing a monthly field survey on certain water wells that are located in a high Andean wet-pasture, where water levels fluctuate a lot due to the nature of the ecosystem. I've been analyzing the data, and the compensated water levels data I get from the levelogger software, is not always the same as the water levels I measure in the field with my water level meter. For example, since september, the data is telling me that the water is rising, but in the field I can see and measure with my water level meter that the water is in fact 0.70 m below that what it used to be.

Someone know a way to identify possible calibration issues with the levelogger? If the levelogger isnt submerged in water anymore even inside the water well, could it cause the sensors to misread the barometric conditions of the well?

Hi, I am wondering if AutoCAD is ever used for hydrology related activities? If so, when?

I am looking to develop skills with softwares that are commonly used in the hydrology field. I will ml begin with HEC-HMS (and probably HEC-RAS) and either ArcGIS or QGIS. Any suggestions on softwares/programs (or anything really) to learn which might be useful in the hydrology field?

I am currently a student, I can likely get both AutoCAD and ArcGIS for free, so wondering if I should take advantage of this while I have the chance.

Hello Again to the helpful community of r/hydrology.

Rather than going into the subreddits of each software, I figured people on here would be able to point me in the right direction.

I am looking to model the impacts of adding additional areas of temporary water storage within a catchment on flood depths, extent, flows etc. I am researching the catchment-scale suitability of using additional temporary water storage to mitigate the impacts of climate change (increased rainfall) on flood risk. I'd be looking to do a "before and after" type comparison to show impacts of additional storage.

Do you know if/how this can be done?

Any input is appreciated. Thanks again guys!

Hello people! I need some help in a problem I'm solving. I'm a environmental engineering student and I'm having a massive problem in solving a problem regarding building a reservoir model. I'd really appreciate if someone can help me in this.

hi everyone, what do u do when hec-hms cant identify streams? i tried to preprocess it in qgis but the strahler order can't seem to connect the streams properly, i edited the channel lines (vector) to manually connect it, but how do you integrate this with the current dem so that hec-hms can recognize it? 🫤 i've read about burning the streams but will it matter once i use it in hec-hms?

I am currently an undergrad hydrogeology major and am in my third year at my school. I’ve received an offer to work for a pretty good civil consulting firm to do water supply management, which is something that I’ve always been interested in. However, i worked in water resource engineering this past summer for a different civil consulting firm and was honestly not into it. As of this year, I’ve become more interested in hydrological science and government agencies that I could try and work for, such as NASA, NOAA, and maybe even the UN. I know these are harder to get internship positions for, but they seem more rewarding as I would get to help pursue water resource sustainability on a national and maybe even global scale. Should I reject this current offer and try to do something that I think im more interested in? Or just say fuck it and take the offer I have.

Hey r/hydrology, I am back again to tap the well of knowledge in this community. This is hopefully an easy one!

I am trying to project additional rainfall volumes for certain rainfall events, in different climate change scenarios, for several river catchments. I have come up with a basic method, but I am worried it's wrong/overly simplified and want to get your take.

The data I have available includes:

•rainfall change projections based on changes from 1981-2000 rainfall base period

•historic daily rainfall depth data for the 1981 - 2000 base period for each river catchment

•historic average daily river flow data for the same base period

•river catchment area

My Method:

1. calculate 50th, 90th, and 99th percentile daily rainfall depths for the base period to represent average, high, and very high rainfall.

2. count the maximum number of consecutive days where rainfall reached or surpassed the 50th, 90th and 99th percentile daily rainfall depths within the base period. This is what I am classing as a "rainfall event". There are no projected changes to rainfall event duration in climate projections, therefore taking it as no change, and using the base period durations.

3. Apply projected rainfall changes to the 50th, 90th, and 99th percentile rainfall depths from the base period.

4. Multiply the rainfall depths calculated in step 3 by the rainfall event duration from step 2 and the river catchment area.

This, I hope, gives projected rainfall event volumes for different scales of rainfall event, in different climate change scenarios.

How does this sound to you guys who actually know about this topic?

Thanks Again if you've made it this far, you guys are the best!

I have a question about HEC-RAS on Linux. I am encountering a “forrtl:severe (174): SIGSEGV, segmentation fault occurred” error with RasUnsteady while running the run_unsteady.sh. Has anyone successfully run unsteady HEC-RAS 2D on Linux and faced this issue? Any suggestions would be greatly appreciated.

This is my first time modeling a site with a creek that runs through it. Specifically I am aiming to get a hydrograph for different return periods and get a volume quantity for detention basin purposes. I'm using hec hms.

My question is, do I need to factor in the creek to obtain this information? The creek has a small amount of standing water under dry conditions, and I don't have any other information on it. All water drains to the exit point where it runs through a culvert that passes underneath a road. Would setting this up simply as two subbasins be an incorrect approach?

Thanks in advance.

Hey! I am undertaking a project on water management and specifically looking at water storage. Is there a reliable way that I could calculate what percentage of total catchment rainfall reaches the reservoirs within the catchment? My water supply company states less than 1%, but to project the impacts that rainfall change may have on future levels, it would be great if there were some way to calculate a reasonably accurate percentage. Any suggestions? Sorry if this is a stupid question, figured I'd ask here before completely ruling it out.

I dont know how to make it. Can you help me to find solution?

I’m currently in community college and I’m trying to pick a major/career and hydrology sounds super interesting as a career. It combines a lot of my interests: water, geology, environmental sciences and a bit of engineering. My only concern is I am very bad at math it doesn’t come to me naturally and anytime I have to do a math class I have to work my ass off. What I have read online that it’s better to have an engineering degree/background with hydrology rather than geology so my question is it worth the struggle to get a background in engineering rather a science one

This is a post for anyone searching for this error in the future, because I could not find any mention of it online and it's been driving me crazy for days now.

If you are running the ArcHydro tool "Create Overland Flow Connectors" tool and getting "Error 000878: Output raster: The length of the grid based name in C:...\scratch\outpth1_... is longer than 13" it's because the script uses the time of day to generate the file name. What you need to do is go into the script and on line 714 go in an edit the output file (I just removed "pth1 and kept the underscore).

This was driving me insane because obviously it doesn't always throw an error. Why the coder decided to do it this way I will never know. But there you go, that's the fix.

Hello. I have a general question as to how you would run a 2-D unsteady flow model in HEC-RAS 6.3.1. given geometries and results. This is for a watershed where rainfall is constantly being applied over an entire day irregularly:

Rainfall over a 1-day period.

I believe rainfall is the sole input that generates flows.

https://preview.redd.it/fpghjk44eg4e1.png?width=443&format=png&auto=webp&s=9c37b3b9b8a100beec01d835182ea2097ffc363e

Current Project Components

Geometries already created:

https://preview.redd.it/5tk8udq5eg4e1.png?width=640&format=png&auto=webp&s=c225d7304d170367c14d56d5fa49d710fbea7953

Pink are boundary conditions and light blue are reference lines.

Results have been run for various design storms:

https://preview.redd.it/db41tkc7eg4e1.png?width=375&format=png&auto=webp&s=f7e30f7778b754973928dfa117980345fcb987b1

Results for the 500,100,50, and 10yr storms Hydrographs

https://preview.redd.it/ktcyjrb9eg4e1.png?width=640&format=png&auto=webp&s=d4c8a3fe2bb0e2932bd2b02c15fbafc3118a487d

My question is how would you use this data to then run simulations for a 2, 5, and 10yr design storm? The goal is to be able to display water surface elevation, water depth, and flow data at another cross section (orange line) (an internal cross-section of one tributary) for these three additional design storms. In other words, how would I apply new rainfall values to generate that same output for water depth/elevation and flows? Would I need to create a unit hydrograph from their rainfall values and associated flows and then scale that to the new rainfall amount or is there a simpler way to go about this? Sorry in advance, I am very new to HEC-RAS 2-D.