Mohammed Jaafar Ali Alatabe

I have found that the US Geological Survey tools and equations very helpful. The tools are often developed by State or physiographic area within States, and based on their extensive network and history in gauging streams across our nation. In addition, they often visit various stations after major floods, identify high water marks, make flood estimates. Learning to identify bankfull indicators can also be helpful, as indicative of the mean annual flood typically every 1-2 years. Dr. David Rosgen suggests from his various studies of stream types, to double the bankfull depth at the thalweg to estimate the 50 year flood. Soil scientists are experienced in identifying alluvial soils and colluvial soil interface, that can also be helpful. Some paleo-geomorphologists have experience in identifying paleo-flood indicators. If you have detailed cross section data and access to associated flow records, you might try out the Rivermorph software. Some people use HEC RAS as a software tool. Some landowners, communities and cultures keep records of local floods, and this can be a good source of information, however some stream and river flooding changes with time due to sediment and other activities. Some forest trees and vegetation withstand flooding, other do not, so this can be another indicator. Since I have always had access to USGS data and tools, as well as collected site data and observations, etc., I generally did not have to rely on other software, but did refer to land use, area based rainfall distribution, aerial photos, topographic DEMs, LiDAR, geology and soil maps, bankfull, debris deposits and other indicators, etc.

These models are available in both open-access and paid ones with different capacities [82,83]. An important concern about hydrodynamic modeling is selecting an appropriate modeling approach. This primarily depends on the purpose of the study, flow conditions, and available data. Geospatial data and techniques have outperformed conventional comprehensive monitoring and assessment approaches, particularly in dynamic and complex urban environments [84]. Despite their benefits, the chaotic and complex nature of floods makes it challenging to develop a credible flood inundation model [85].

https://www.mdpi.com/2073-445X/12/3/627

Generally the flood or water managers would prefer customised tools because off the shelf software cannot provide for the heterogeneities of soil water behaviours and then to incorporate the stakeholder expectations. As most flood management institutions do not have sufficient inhouse experts, these customisation tasks are outsourced and new products are developed on Contract. However such products or details of product development or the utilisation of such products do not get reported since they are not public domain information (have copyrights). Unconfirmed information is that such customisations do not lead to sustainable continued products due to development issues, contractual issues, maintenance agreement issues etc. Hence instead of developing sustainable tools by learning from others, most tools use off-the-shelf application software and then reinvent the wheel. This individual and independent reinventing efforts lead to unproductive work and hence, poorly contribute to the efforts of flood and water management. We all should try to get the customisation efforts into light and capture the reason for unsuccessfulness of such customisations. or unsustainability of such customisations.

William F. Hansen thank you very much for sharing your experience. If it is possible can you give a your comments on following,

1. Are those tools totally match your practical work (means the tools provide the required sequence of the process) or

2. do you utilise the tools to get the required results in the different steps of the process

3. what do you think of the idea given by Sohan Nallaperuma Thantrige Wijesekera above?

thank you very much

I have been very fortunate to be involved with experimental watersheds, gauging streams and interacting at times with Official stream gauges, installing, measuring flow, data analysis, etc. In the US, the US Geological Survey is the preeminent agency for this work, and the US Forest Service and many Universities, and States set up their own experimental catchments, or specific needs for stream gauging, water balance, flood and drought estimates, and often rainfall and other meteorological associated data. The long term network of water based stations has been relied heavily upon. The guidance provided by USGS based on this information is extremely helpful, but as suggested by other commenters, hydrologic analysis may include other factors. My training, experience did not depend on flood models or software for the most part. It was more data based, observational and included site evaluations, such as for culverts, bridges or other crossings, evaluation of floodplain or flood prone areas for example. To the greatest extent, estimates of flooding had a strong relationship to watershed size, with considerations associated with physiographic area, topography and rainfall amount and frequency data. Presence of accumulations of large wood, signs of excess sediment or bedload, potential of landslides would be some of the considerations in assessing conditions. I would recommend if models are used, to try to validate them first with existing data available. If no data, when you drive your roads and highways, as you come by stream crossings, try to find when they were installed, have they failed or been overtopped/damaged, measure their size, use GIS or topographic maps to determine watershed size, aerial photos for land use, geology and soil maps, if you have time bankfull and floodplain cross section, any local information on past flood(s), etc. If you ever have a major flood, when travel is safe, drive the roads, looking for flood water marks, signs of culvert or bridge overtop with deposited debris, sediment, damage. Flood gauging high water can also be done with crest gauges. If culverts and bridges remain in place for many years or the structure lifetime, the local guidance is probably sufficient.