Hydrologic and Hydraulic Analysis. Conduct required H&H analyses to assess existing and proposed conditions. Analyses should be performed for the 2-year (50% annual exceedance probability (AEP)), 10-year (10% AEP), 100-year (1% AEP), and 500-year (0.2% AEP) storm events. The existing condition modeling will be based on the Xxxx-Xxxxxx Big Creek model completed in 2020 for Fort Bend County. This model includes updated rainfall per recent revisions to Atlas
Hydrologic and Hydraulic Analysis. Rapid 2D Assessment
Hydrologic and Hydraulic Analysis. This project is located in the Floodway of the West Fork Trinity River and within the Trinity Corridor Development Certificate (CDC) floodplain boundary. The preliminary alignment of the trail crosses the Unnamed Tributary to the West Fork Trinity River as well as the Unnamed Tributary to Walnut Creek 2. The trail is also located within the FEMA SFHA floodway of the West Fork Trinity River. Due to the location of the project, permitting applications are required through the City, TXDOT and the CDC. The project is not anticipated to cause changes to the FEMA floodplain or floodway, so a CLOMR/LOMR is not included in the scope of this project. The items below describe our understanding regarding drainage for the scope of this project.
1. Data Collection and Site Visit - Collect and review available information, including GIS data, existing models and proposed trail plans and perform one site visit
2. FNI will model any proposed changes to the West Fork Trinity River using the effective CDC model updated May 2013. FNI will compare the results to determine impacts to water surface elevations and valley storage, if any, to the West Fork Trinity River.
3. FNI will submit a Floodplain Development Permit and No Rise Certificate to the City and will coordinate with the City Floodplain Administrator for approval. A cut/fill balance will be provided to show no net loss in storage within in the floodplain.
4. FNI will submit a flood study in the form of a technical memorandum documenting the results from the hydraulic analysis to be submitted with the Floodplain Development Permit to the City and to TXDOT Fort Worth District.
5. FNI will address City comments on the flood study and floodplain development permit.
6. FNI will prepare and submit Part I of the CDC permit. It is assumed that this project will be considered “small-scale” and be eligible for a variance to the CDC permit. Part II of the permit process will be additional services, if a variance is not granted. FNI will coordinate with the City’s Floodplain Administrator for approval. The CDC permit application process will not begin until 60% design plans are available.
7. FNI will address up to one round of comments for the CDC permit.
8. FNI will coordinate with the Section 404 permitting requirements and TXDOT Categorical Exclusion documents.
9. FNI will submit a memo stating that the bridges shall be protected to prevent scour. Modelling and a full scour analysis will be considered additional services. A s...
Hydrologic and Hydraulic Analysis. Data Collection for Hydrology/Hydraulic Tasks: Hydrology and Hydraulic Modeling
Hydrologic and Hydraulic Analysis. Since Task 3 includes development and evaluation of alternatives, to some extent, it must occur concurrently with Task 5, Preliminary Design. After the initial review of flooding issues and potential treatment facilities with the City, we propose that the design team and the City conduct a series of meetings to develop alternatives and specific information needs to confirm that each alternative is indeed technically feasible. Many objectives, such as stabilizing road shoulders and replacement of undersized storm drains, will be straightforward and will not require such an approach. However, development of alternative treatments related to the location and function of treatment basins, possible stormwater diversions, and floodplain restoration measures will be most effectively done using a team approach to identify information needs and to also provide an initial assessment of cost feasibility where easements or land acquisitions may be required. In essence, we propose an alternative development and feasibility screening process as an additional Task 3 subtask. We believe this will reduce costs associated with surveying, geotechnical, and NEPA/CEQA analysis as the design progresses. The stormwater treatment facilities designed as part of the alternatives analysis shall at a minimum capture, treat, and infiltrate storm water runoff from the 550-acre contributing drainage area (watershed) and infiltrate 72 acre-feet of stormwater. We propose to undertake Task 3.2 as shown in the RFP prior to initiation of Task 3.1 since it provides the information prerequisite to the design process.
Hydrologic and Hydraulic Analysis. The horizontal screen design process must include an analysis to verify that sufficient hydrologic and hydraulic conditions exist in the stream so as not to exacerbate a passage impediment in the stream channel (see Section 4.1), or in the off- stream conveyance, including the screen and bypass. This analysis must conclude that all criteria listed below can be achieved for the entire juvenile outmigration season, as defined by section 3. If the criteria listed below cannot be maintained per this design analysis, a horizontal screen design must not be used at the site. If this analysis concludes that removal of the bypass flow required for a horizontal screen from the stream channel results in inadequate passage conditions or unacceptable loss of riparian habitat, other screen design styles must be considered for the site and installed at the site if adverse effects are appreciably reduced.
Hydrologic and Hydraulic Analysis. The existing and proposed condition XPSWMM models within the City’s Storm Drain Master Plan will be reviewed and adjusted to facilitate the final design of the preferred alternative storm drain alignment. It is anticipated that the proposed condition models will include identifying a new storm drain alignment that will route flows to the North Truckee Drain. As part of this realignment, an inlet analysis will be performed. If the proposed storm drain cannot be constructed or design criteria cannot be met to meet City standards due to utility location or other constraints, coordination with the City will be conducted to determine the optimal design condition. It is assumed that: • Drop inlet locations will not change in the proposed condition and that an analysis will not be required as no known problems exist in this area. • Drainage basins will not be modified from the master plan basins. • Tailwater conditions on the North Truckee Drain will be evaluated for the design and agreed upon with the City. • While the City’s Storm Drain Master Plan was modeled with XPSWMM, the City may want the final design completed with InfoSWMM. The post-project hydraulic analysis results will be summarized in Task 5 to identify the additional storm drain capacity that will be achieved with the construction of this project. In addition, the final report will show that there will be no adverse impacts associated with the preferred design.
Hydrologic and Hydraulic Analysis. Inter‐Fluve will review the existing one‐dimensional HEC‐RAS model and modify based on updated survey information. The existing conditions model will cover the entire project area. The model will be run for a series of flow events (base, 1.5, 2, 10, 25, 50, 100 and 500‐year return interval flows). Boundary conditions will be examined for the project reach. Inter‐Fluve will develop proposed conditions and model the necessary design iterations appropriate for final design.
Hydrologic and Hydraulic Analysis. 4.1. Perform a hydrologic analysis of the Sheridan Drain and unnamed tributary (UNT) to the Upper Trier regulated drain watersheds. The analysis will separate the watershed into a maximum of six subareas. Existing and proposed condition flow rates will be determined for the 10%, 2%, and 1% exceedance probability storm events. The proposed watersheds will include as much of the Sunnymede Subdivision that is able to be discharged to the selected outfalls. The calculation methodology will be determined based on the watershed characteristics and the Allen County Stormwater Technical Standards Manual.
4.2. Perform a hydraulic analysis of the Sheridan Drain conveyance system within the project limits using HEC-RAS. This analysis will include the following:
4.2.1. Determination of appropriate boundary conditions. This will include a joint probability analysis with the Maumee River.
4.2.2. Development of an existing conditions model which will include approximately 6,550 feet of drain and 11 crossings.
4.2.3. Development of a proposed conditions model which will include improvements to the conveyance capacity and alignment of the channel and structures as appropriate. Proposed structures will be sized using applicable standards (i.e., local, State, or railroad) for each crossing.
4.2.4. Evaluation of remaining capacity in the proposed system. Based on this, recommendations will be made regarding potential future development areas that could be drained to the proposed system.
4.3. Perform a hydraulic analysis for a proposed alternative to discharge stormwater to the Upper Trier via an enclosed system generally running parallel to the existing unnamed drain located along Maplecrest Road approximately 0.5 miles south of State Road 930. This analysis will include the following:
4.3.1. Determination of appropriate boundary conditions. This will include a joint probability analysis with the Upper Trier.
4.3.2. Preliminary sizing for a proposed system of stormwater piping to discharge the Sunnymede Subdivision watershed area to the Upper Trier.
4.4. The methodologies and results of the hydrologic and hydraulic analysis will be documented in a hydraulic memo. This memo will be stamped by a licensed Professional Engineer and will be suitable for submittal to INDOT and the railroad as part of the anticipated permitting requirements.
Hydrologic and Hydraulic Analysis. Hydrologic and hydraulic analysis will continue building off of the efforts completed during Phase 1 in order to investigate new alternatives introduced during the later stages of 30% design and support design development as it moves through 60% and 90% detail levels.
