Hello everyone,

I'm a recent civil engineering grad who currently works for the local DOT as a hydraulics engineer. Our department is in the process of starting to use PCSWMM as our primary software for getting our design flow values for our culverts.

My question is, when modeling we start with a DEM file of the study area and then we use the built-in Watershed Delineation Tool. This tool breaks down the study area into multiple sub-catchments and assigns it different parameters such as area, width and slope based on the DEM file.

For the slope value it assigns it thr average slope of the sub-catchment, but should I be manually calculating the slope of just the channel withing each sub-catchment?

Thanks in advance!

Does anyone else get really high shear stress values in the model? Like above 1PSI. Am I missing something with stable channel design? Doesn't that calculate to 144 lb/ft2 where even concrete or rip-rap wouldn't be enough for withstand those stresses? I feel like I am missing something. Any thoughts?

Edit: I solved my own problem. HEC-RAS 6.3 had a bug for 2D profile lines that was plotting PSI instead of pounds feet that we all use for stable channel design (call it PFT???). Anyways, its fixed, and later versions plot correctly.

Hello,

I am a student currently trying to determine runoff curve numbers for a site. Using TR55 worksheets, they require a designation of land cover along with the hydrologic soil group. Is the best way to determine this land cover using the scale to determine the areas of different uses based on the aerial image, or is there a resource similar to the hydrologic soils group map via the USGS available for land cover designation?

Hello! Is there a minimum value for baseflow index (bfi)? Based on my results, annual bfi varies between 0.4-0.75 but there was one year whose value is 0.048. Is this value still acceptable or is not realistic. Thanks!

Can someone recommend an excellent course on hec ras 2D.online

Good day!

I am currently a college student and I am interested in estimating an inflow hydrograph for a reservoir. Can I use a Digital Terrain Model and rainfall data? What softwares should I use? I would appreciate if someone answers in this post. Thank you!

I understand generally what they do but having examples of projects would be nice. For it really helps. It's how i came to understand seismologists and stuff better.

Anything to read would be great

Hi guys,

I am looking for download feflow but I could not find any link to download free the feflow.

Do you have sth there?

Regards!

Hi everyone. I am working on a parcel of land in Florida that has a partial designation of AE - 5 on the FEMA map. It appears that the extent of the FEMA floodplain line goes well above the actual 5' contours of the property. The agencies are only going by the FEMA floodplain map and in their eyes the extent of the floodplain is where it is shown on the FIRM. In order to have this adjusted, is my only recourse to submit a LOMC to FEMA and does anyone have an idea on the length of time to get a LOMC approved once submitted? Thank you for any assistance and help! :)

Hi all. This is a followup from an old post.

Does anyone know how to download CHAMP (Coastal Hazard Analysis Modeling Program)? It seems like all the links via FEMA are dead.

Novice here so any comments please consider that I am totally new to this space.

I'm working on a project where I am looking to estimate the flood depth for specific geolocations. In this particular example I am looking at:

latitude = 32.786750
longitude = -96.794950

I know that FEMA provides Geodatabase, tif and shapefiles for specific areas, but they aren't available for all areas. For the specific location that I choose above Flood risk data is available so I have chosen it as a reference point.

The base flood elevation for the geolocation above is approximately 471.2ft (NAVD 1988) as provided here: https://webapps.usgs.gov/infrm/estbfe/report.html?lat=32.78675&lng=-96.79495&theme=dark

However, in the FEMA NFHL state file for Texas (Product ID: NFHL_48_20241230) the estimated base flood elevation (using the S_BFE layer) is approximately 427ft for the same location (my screen shot from Geopandas is below).

My question is, why would there be such a huge difference in estimated base flood elevation? The difference is large enough for me to believe I am doing something wrong. Can you point me in the right direction?

Also, im using Python as I need to be able to do this in an automated way.

Thanks in advance!

https://preview.redd.it/op19j2xvjebe1.png?width=517&format=png&auto=webp&s=a7c382af1c346650f7728255db431de234fab658

Curious on what everyone's take is on hydraulic/hydrological software. I currently use Tuflow, in grad school and with other companies I used Mike, SWMM, Arc Hydro,IRIC, HEC-RAS/HMS, SRH-2D, optimatics XPSWMM/PCSWMM. Down to the nitty gritty, I always prefer hand calcs/spreadsheets checks or python and my own judgement. Sometimes, models tend to just be models and not fundamental enough for my sanity, but billable hours are billable hours.

I know flood modelling is very model based, but other applications like pipe and channels can have a bit of both depending on the problem at hand, and scour problems are reliant on cfd setups. I was curious, what's everyone's opinion on the state of the art tools, and preferred tools?

I am an intermediate with a little bit of knowledge in geotech/channel & integrated hydraulics, but there's so much to learn out there! I'm looking nto the comunity to see what you all think. --Also tuflow vs Mike??

Hello people, I have some issues defining the runoff coefficient for a specific area, which is 'gardening above basement', while using the rational method, for open area gardening I usually use 0.3-0.4, but let's assume that if it's above the parking basement, it has a certain depth of soil (not sure how much, it might affect the coefficient) let's say at least 1 meter depth. is it okay to still consider it 0.4? or because it's not going to the groundwater it by definition needs to be higher? but when the rain starts, the soil can hold the water and contribute much less than 0.9 (like asphalt), and It can evaporate and contribute less runoff... I'm planning for a 24-hour duration storm? It all depends on the duration of the storm I'm designing? thanks for the help [=

sometimes when boiling toluene w/ my bro's tend 2 4get that spar-me luvs to boil the living daylights outta things till they explode √°^°\ #PROTONatersANONYMOUS

-OGKetamin3Dreamz

I'm somewhat active on r/chemistry but I recently found this sub and am curious if some of the water chemistry questions are better answered here.

Specifically, someone in Colorodo Springs, CO noticed that their aquarium had a high nitrate and nitrite level.

They are using API 5-in-1 strips and I can't find the method API uses. It might be a false positive.

They did repeat testing to confirm, tested their tap water (same high nitrate/nitrite) and tested a control (bottled water) with normal values. The water quality report (best I could find) reports a nitrate of < 1 mg/L.

Their tank looks fine - they tested out of curiosity. Nothings dying and the nitrite is returning at 5 ppm for tap and tank, and the nitrate is higher (40-80 ppm).

So, what's happening here? False positive? If so, what might be the contaminant? I really feel like we are overlooking something here.

https://theclimateaccordingtolife.substack.com/p/millan-millan-and-the-mystery-of

After reading this article about Millan Millan's work I've gone down somewhat of a fascinating rabbit hole about how landuse change affects the water cycle and also the climate. I work as a water resources engineer and was familiar with the effects of rainfall-runoff processes but wasn't aware of how this affects the "small water cycle" in terms of generating precipitation. I also wasn't aware that the changes in the water cycle could have such a large effect on warming. I found one study that said that up to 18% of observed warming today can be attributed to landuse change rather than atmospheric carbon. The article argues this is largely ignored because it's a lot easier to draw a direct link to those causing landuse changes whereas atmospheric carbon is a bit more abstract.

Was curious to get thoughts on this topic from this subreddit. Has anyone got any good recommendations of books, studies or reports to read more about these ideas?

This is first time for me using HEC-HMS. I has an assignment to perform basic hydrological analysis of "Subasin 10". Unfortunately I don't have streamflow data of that catchment. I have stream flow data of other 4 breakpoints towards the right of the catchment but not for same time period.
So my question is, do I need to input all the known rainfall and streamflow data or just the shortest time period for which i have the streamflow of (Reach 1: 1996-2010)?

Greetings, I have been looking at houses for sale in a neighborhood that was thinking of buying, and I noticed on FEMA's website they have a blue box around some houses, and I was wondering if that means that the houses located inside the blue box are in a flood plain area? I assume the answer is yes, however I am not an expert and don't want to jump to conclusions as I am uneducated with this topic and am trying to learn about it before making a purchase. Near by is a small creek and a soccer field and some grassy parks, nature preserve. My goal is to buy a house not located in a flood area. Thank you for your help and your time!

Hey r/hydrology!

I am hoping for a bit of advice from those more experienced in the art of Hydrology.

I am trying to calculate additional runoff volumes from rain falling on river catchments under different climate change scenarios (2.6rcp, 4.5rcp etc.).

I have a few questions that I'd be grateful of your recommendations on.

1. How would you recommend I calculate additional rainfall volumes? and for which events would be best? I currently use 50th, 80th, 90th and 99th percentile daily rainfall depth values from the base period to give a range of rainfall depths from average (50th), to significant (80th), to high (90th) and then very high (99th). I then multiply by the max consecutive days daily rainfall reached the aforementioned percentile values within the base period to get event volumes. I feel this is not the best way to do it, but can't find anything better.

2. How do you recommend I account for runoff and infiltration at a catchment scale? I know there are several methods like the curve number and the rational method, but wanting to know if you'd recommend a set method. Doesn't have to be too accurate, I am looking to give approximate values and can state uncertainties in my research.

The data I have to work with to try and make approximate projections are as follows:

Historic daily rainfall data for catchment guagung stations

Climate projections showing rainfall increases

CORINE EU land use data

DTM & DSM data

Thank you so much for taking the time to read this, and any advice would be greatly appreciated. I apologise if I am over simplifying this slightly, I am doing a research project as it is a field I am interested in, but obviously don't have the knowledge or time to go too in depth, hence why I'm looking to do some basic projections and not too worried about them being highly accurate.

Thanks for your time

Happy New Year alll! I'm a college student studying Hydrology, still making my way through prereqs before I start learning the tools of the trade or getting job/internship experience. I was wondering what you all think may be some commonplace software/programs that I should get myself familiar with so that I could be useful when I finally get a position, or to get ahead with my studies?

Specifically, what context have people used the outputs of this model? I'm vaguely familiar with mission behind Riverscape, but haven't ran the model myself to truly understand what benefits the outputs provide.

Hi there! I have a study about determining the impacts of baseflow to the flood occurrences/behaviour of a river with the aim of identifying the role of groundwater via baseflow in driving floods. I have temperature, precipitation, and baseflow obtained from daily streamflow data of 13 years. A similar study I read implemented quantile regression analysis, are there other specific ways/method i could use to perform the study and show how baseflow affects flooding? Thanks a lot!

Hello everyone, I am currently working in IBER software. Every postprocess animations seems fine. The animations such as velocities or suspended transport are going on right in the channel (as it should be), but in the case of erosion, I can see the erosion in the river channel but in the shapefile there is this blue fill. Anybody know what to do?

https://preview.redd.it/limjp8vpaz9e1.png?width=1259&format=png&auto=webp&s=29407047a8db4dfffe1deab50f644b0204256c98